  United States Court of Appeals
      for the Federal Circuit
                ______________________

       LIGHTING BALLAST CONTROL LLC,
               Plaintiff-Appellee,


                           v.


    PHILIPS ELECTRONICS NORTH AMERICA
               CORPORATION,
                 Defendant,


                         AND



 UNIVERSAL LIGHTING TECHNOLOGIES, INC.,
            Defendant-Appellant.
                ______________________

                      2012-1014
                ______________________

   Appeal from the United States District Court for the
Northern District of Texas in case no. 09-CV-0029, Judge
Reed O’Connor.
                ______________________

              Decided: February 21, 2014
               ______________________
2                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


    ANDREW J. DHUEY, of Berkeley, California, argued for
plaintiff-appellee on rehearing en banc. With him on the
brief were JONATHAN T. SUDER and DAVID A. SKEELS,
Friedman, Suder & Cooke, of Fort Worth, Texas; and
ROBERT P. GREENSPOON, Flachsbart & Greenspoon, LLC,
of Chicago, Illinois.

    STEVEN J. ROUTH, Orrick, Herrington & Sutcliffe LLP,
of Washington, DC, argued for defendant-appellant on
rehearing en banc. With him on the brief were STEN A.
JENSON, JOHN R. INGE, T. VANN PEARCE, JR., and DIANA M.
SZEGO.

    NATHAN K. KELLEY, Solicitor, United States Patent
and Trademark Office, of Alexandria, Virginia, argued for
amicus curiae United States on rehearing en banc. With
him on the brief were KRISTI L. R. SAWERT and ROBERT J.
MCMANUS, Associate Solicitors. Of counsel on the brief
was Mark R. Freeman, Attorney, Appellate Staff, United
States Department of Justice, of Washington, DC.

    LAUREL G. BELLOWS, American Bar Association, of
Chicago, Illinois, for amicus curiae American Bar Associa-
tion on rehearing en banc. With her on the brief were
ROBERT F. ALTHERR, JR. and PAUL M. RIVARD.

    CHARLES W. SHIFLEY, Banner & Witcoff, Ltd., of Chi-
cago, Illinois for amicus curiae Intellectual Property Law
Association on rehearing en banc.

     CHIDAMBARAM S. IYER, Sughrue Mion, PLLC, of Wash-
ington, DC, for amicus curiae Sigram Schindler Be-
teiligungsgesellschaft mbH on rehearing en banc.

    ROLF O. STADHEIM, Stadheim & Grear Ltd., of Chica-
go, Illinois, for amici curiae NUtech Ventures, Inc., et al.
LIGHTING BALLAST   v. PHILIPS ELECTRONICS               3


on rehearing en banc. With him on the brief was GEORGE
C. SUMMERFIELD.

    JOHN W. SHAW, Shaw Keller LLP, of Wilmington, Del-
aware, for amicus curiae Delaware Chapter of the Federal
Bar Association on rehearing en banc. With him on the
brief was KAREN E. KELLER.

    HARRY C. MARCUS, Locke Lord, LLP, of New York,
New York, for amicus curiae American Intellectual Prop-
erty Law Association on rehearing en banc. With him on
the brief were ROBERT K. GOETHALS and JOSEPH A. FARCO.
Of counsel on the brief was JEFFREY I.D. LEWIS, Americn
Intellectual Property Law Association, of Arlington,
Virginia.

    JOHN D. VANDENBERG, Klarquist Sparkman, LLP, of
Portland, Oregon, for amicus curiae Microsoft Corporation
on rehearing en banc. With him on the brief was ANDREW
M. MASON.

    DARYL L. JOSEFFER, King & Spalding LLP, of Wash-
ington, DC, for amici curiae Google Inc., et al. on rehear-
ing en banc. With him on the brief were KAREN F.
GROHMAN, of Washington, DC; and ADAM M. CONRAD, of
Charlotte, North Carolina.

    THOMAS G. HUNGAR, Gibson Dunn & Crutcher LLP, of
Washington, DC, for amici curiae Cisco Systems, Inc., et
al. on rehearing en banc. With him on the brief were
MATTHEW D. MCGILL and ALEXANDER N. HARRIS.

     JENNIFER KUHN, Law Office of Jennifer Kuhn, of Aus-
tin, Texas, for amicus curiae Austin Intellectual Property
Law Association on rehearing en banc. Of counsel on the
4                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


brief was ADEN M. ALLEN, Wilson Sonsini Goddrich &
Rosati PC, of Austin, Texas.

     JOSEPH R. RE, Knobbe, Martens, Olson & Bear, LLP,
of Irvine, California for amicus curiae Federal Circuit Bar
Association on rehearing en banc. With him on the brief
were JOSEPH M. REISMAN and SHELIA N. SWAROOP. Of
counsel on the brief was TERENCE STEWART, President,
Federal Circuit Bar Association, of Washington, DC.

    R. CARL MOY, William Mitchell College of Law, of
Saint Paul, Minnesota, for amicus curiae Intellectual
Property Institute of William Mitchell College of Law on
rehearing en banc.

    ANDY I. COREA, St. Onge Steward Johnston & Reens
LLC, of Stamford, Connecticut, for amicus curiae Con-
necticut Intellectual Property Law Association on rehear-
ing en banc. With him on the brief were STEPHEN P.
MCNAMARA and TODD M. OBERDICK.

   CHARLES HIEKEN, Fish & Richardson P.C., of Boston,
Massachusetts, for amicus curiae Paul R. Michel on
rehearing en banc. With him on the brief was JOHN A.
DRAGSETH.

    JANET B. LINN, Eckert Seamans Cherin & Mellot,
LLC, of White Plains, New York, for amicus curiae Asso-
ciation of the Bar of the City of New York on rehearing en
banc.

    PAUL H. BERGHOFF, McDonnell Boehnen Hulbert &
Berghoff, LLP, of Chicago, Illinois, for amicus curiae
Intellectual Property Owners Association on rehearing en
banc. With him on the brief was CHRISTOPHER D. BUTTS.
Of counsel on the brief were RICHARD F. PHILLIPS and
LIGHTING BALLAST   v. PHILIPS ELECTRONICS              5


KEVIN H. RHODES, Intellectual Property Owners Associa-
tion, of Washington, DC. Of counsel was HERBERT C.
WAMSLEY, JR.

    WILLIAM L. RESPESS, San Diego Intellectual Property
Law Association, of Rancho Santa Fe, California, for
amicus curiae San Diego Intellectual Property Law Asso-
ciation on rehearing en banc.

    MAXIM H. WALDBAUM, Eaton & Van Winkle LLP, of
New York, New York, for amicus curiae Fédération Inter-
nationale Des Conseils En Propriété Intellectuelle (FICPI)
on rehearing en banc. With him on the brief was ROBERT
D. KATZ.

    PETER S. MENELL, University of California at Berke-
ley School of Law, of Berkeley, California, for amicus
curiae Professor Peter S. Menell on rehearing en banc.

    ROGER L. COOK, of San Francisco, California, for ami-
cus Ad Hoc Committee of Patent Owners in the Lighting
Industry on rehearing en banc.
                 _____________________

              ON REHEARING EN BANC
                   _____________________
   Before RADER, Chief Judge, NEWMAN, LOURIE, DYK,
    PROST, MOORE, O’MALLEY, REYNA, WALLACH, and
              TARANTO, Circuit Judges. *




   *    Circuit Judges Chen and Hughes took no part in
the consideration or decision of the case.
6                      LIGHTING BALLAST   v. PHILIPS ELECTRONICS


    Opinion for the court filed by NEWMAN, Circuit Judge,
    with whom LOURIE, DYK, PROST, MOORE, and TARANTO,
                     Circuit Judges, join.
          Concurring opinion filed by LOURIE, Circuit Judge.
      Dissenting opinion filed by O’MALLEY, Circuit Judge,
      with whom RADER, Chief Judge, and REYNA and
               WALLACH, Circuit Judges, join.
NEWMAN, Circuit Judge.
    The court en banc granted the petition filed by pa-
tentee Lighting Ballast Control, in order to reconsider the
holding in Cybor Corp. v. FAS Technologies, Inc., 138 F.3d
1448 (Fed. Cir. 1998) (en banc) establishing the standard
of appellate review of district court decisions concerning
the meaning and scope of patent claims—called “claim
construction.” Implementing the Supreme Court’s deci-
sion in Markman v. Westview Instruments, Inc., 517 U.S.
370 (1996) (Markman II), aff’g Markman v. Westview
Instruments, Inc., 52 F.3d 967 (Fed. Cir. 1995) (en banc)
(Markman I), this court in Cybor held that patent claim
construction receives de novo determination on appeal,
that is, review for correctness as a matter of law. Such
review is conducted on the administrative record and any
additional information in the record of the district court,
and is determined without deference to the ruling of the
district court.
    In the case now before us, a panel of this court fol-
lowed the Cybor standard and revised the district court’s
claim construction, applying de novo the statutory re-
quirements of 35 U.S.C. §112 ¶6 and §112 ¶2. 1 Briefly,

      1Lighting Ballast Control, LLC v. Philips Electron-
ics North America Corp., No. 7:09-CV-29-O, 2010 WL
4946343 (N.D. Tex. Dec. 2, 2010), rev’d, 498 Fed. App’x
LIGHTING BALLAST   v. PHILIPS ELECTRONICS               7


the panel held that the claim term “voltage source means”
is a means-plus-function term requiring corresponding
structure in the specification. On this claim construction,
the panel reversed the district court and held the claims
invalid for indefiniteness. The patentee requests rehear-
ing, stating that on deferential appellate review the
district court would not or should not have been reversed.
This court undertook rehearing en banc for the purpose of
reconsidering the standard of appellate review of claim
construction.
     For the reasons we shall discuss, we apply the princi-
ples of stare decisis, and confirm the Cybor standard of de
novo review of claim construction, whereby the scope of
the patent grant is reviewed as a matter of law. After
fifteen years of experience with Cybor, we conclude that
the court should retain plenary review of claim construc-
tion, thereby providing national uniformity, consistency,
and finality to the meaning and scope of patent claims.
The totality of experience has confirmed that Cybor is an
effective implementation of Markman II, and that the
criteria for departure from stare decisis are not met.
                              I
               THE REHEARING ARGUMENTS
    Lighting Ballast argues that de novo plenary deter-
mination of claim construction is improper appellate
practice, stating that the interpretation of documents is
fundamentally factual in nature, and that the district
court’s interpretation of patent claims requires deference
on appeal. Lighting Ballast states that on deferential
review the district court’s claim construction for the


986 (Fed. Cir. 2013), withdrawn, 500 Fed. App’x 951 (Fed.
Cir. 2013).
8                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


patent in suit would be sustained, along with the ensuing
judgment that the claims in suit are valid and infringed.
     This en banc court agreed to reconsider the principle
of de novo review of claim construction, and invited sup-
plemental briefing and amicus curiae participation on the
following questions:
        (1) Should this court overrule Cybor?
       (2) Should this court afford deference to any
    aspect of a district court’s claim construction?
        (3) If so, which aspects should be afforded
    deference?
    The parties as well as the amici curiae were not of one
mind, but divided among three general views, all thought-
ful and well presented. 2 The general positions are sum-
marized:


    2    Thirty-eight entities participated as amici curiae
in twenty-one briefs. The participants are: Amazon.com,
Inc.; American Bar Association; American Intellectual
Property Law Association; Austin Intellectual Property
Law Association; Association of the Bar of the City of New
York; Association of University Technology Managers;
Cisco Systems Inc.; Colorado State University Research
Foundation; Connecticut Intellectual Property Law Asso-
ciation; Delaware Chapter of the Federal Bar Association;
Dell Inc.; EMC Corporation; Federal Circuit Bar Associa-
tion; Fédération Internationale Des Conseils En Propriété
Intellectuelle; Google Inc.; Hewlett-Packard Co.; Intel
Corporation; the Intellectual Property Institute of Wil-
liam Mitchell College of Law; the Intellectual Property
Law Association of Chicago; the Intellectual Property
Owner’s Association; former Chief Judge (ret.) Paul R.
LIGHTING BALLAST   v. PHILIPS ELECTRONICS               9


The first view
    The view favored by Lighting Ballast is that the Cybor
decision is incorrect and should be entirely discarded.
Lighting Ballast argues that this court in Cybor misap-
plied the Supreme Court’s decision in Markman II, in that
the Court had focused only on whether questions of patent
claim construction are subject to jury trial, or whether
this issue should be decided solely by a judge. These
proponents state that the Court in Markman II, in decid-
ing the judge-jury question, did not change the traditional
distinction between fact and law, recognized that there
are factual aspects of claim construction, and did not
address the standard of appellate review.
    These proponents argue that the Court left intact the
protocol of appellate deference to a district court’s fact-
based rulings, whether the facts relate to claim construc-
tion or any other issue, and whether the ruling is by a
judge or by a jury. They state that the Cybor standard of
plenary appellate review is incorrect, and remind us that
the Court in Markman II described claim construction as


Michel; Professor Peter S. Menell; Microsoft Corp.; New-
South Innovations; NUTech Ventures, Inc.; Patent Own-
ers in the Lighting Industry; Public Patent Foundation;
Red Hat, Inc.; San Diego Intellectual Property Law Asso-
ciation; SAP America Inc.; SAS Institute Inc.; Sigram
Schindler Beteiligungs GmbH; the Science & Technology
Corporation at the University of New Mexico (STC.UNM);
the University of Nebraska Medical Center Technology
Transfer Corporation (UNeMed Corp.); Wisconsin Alumni
Research Foundation; TEC Edmonton; the University of
Pittsburgh; the United States; and Yahoo! Inc. At the
court’s invitation, the United States participated in the
argument.
10                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


a “mongrel practice” of law and fact with “evidentiary
underpinnings,” 517 U.S. at 378, 390. They argue that
although the Court stated that “the interpretation of a so-
called patent claim . . . is a matter of law reserved entirely
for the court,” id. at 372, the Court did not strip claim
construction of its essentially factual nature.
     These proponents point out that in construing patent
claims, expert testimony and documentary evidence may
be presented to the district court. They argue that resto-
ration of deferential appellate review on the clear error
standard would not only respect the traditional tri-
al/appellate relationship, but also is more likely to give
weight to aspects involving credibility of witnesses. They
point out that Federal Rule of Civil Procedure 52(a)(6)
requires that the district court’s factual findings receive
review on the deferential clearly erroneous standard, 3
citing Pullman-Standard v. Swint, 456 U.S. 273, 287
(1982) for its statement that Rule 52(a) “does not divide
findings of fact into those that deal with ‘ultimate’ and
those that deal with ‘subsidiary’ facts.”
    These proponents argue that patent claim construc-
tion is most reasonably classified as a question of fact,
and that the Court’s Markman II description of claim
construction as better suited to determination by a judge
rather than a jury does not affect the requirement of
appellate deference to findings of fact made at the trial
level. Thus Lighting Ballast urges that the Cybor stand-



     3   Rule 52 (a)(6) Setting Aside the Findings. Find-
ings of fact, whether based on oral or other evidence, must
not be set aside unless clearly erroneous, and the review-
ing court must give due regard to the trial court’s oppor-
tunity to judge the witnesses’ credibility.
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                11


ard of de novo review is incorrect and should be entirely
discarded.
The second view
     The second approach, favored by some amici curiae
including the United States, may be viewed as a fusion or
hybrid of de novo review and deferential review. These
proponents acknowledge that the Court in Markman II
described patents as “legal instruments” and stated that
interpretation of patent claims is a “purely legal” matter,
517 U.S. at 391, but argue that the correct appellate
approach is for the factual aspects of claim construction to
be reviewed on the clearly erroneous standard, while the
final conclusion receives review as a matter of law. See,
e.g., Brief of Amicus Curiae United States at 4 (“Because
Cybor fails to acknowledge that claim construction may
involve factual findings entitled to deferential review
under Rule 52(a), it should be overruled. But this Court
should reaffirm that the ultimate construction of a patent
claim is a legal conclusion subject to de novo review.”).
The United States draws analogy to the ruling in the
regulatory tariff case of Great Northern Railway Co. v.
Merchants’ Elevator Co., 259 U.S. 285, 292 (1922), that
when ambiguity arises in the construction of certain legal
instruments, the ambiguity is resolved as a question of
fact.
    Some of these amici recognize that difficulties may
arise in practice, in knowing which aspects of the district
court’s claim construction are subject to deferential review
and which aspects receive de novo determination. They
suggest a solution whereby the standard of review would
depend on whether the district court’s claim construction
drew solely from the record of the patent and its prosecu-
tion history (called “intrinsic evidence”), or whether
external information or witness testimony was presented
in the district court (that is, “extrinsic evidence”). Apply-
12                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


ing this distinction, some amici propose that claim con-
structions based on extrinsic evidence would receive
clearly erroneous review, for such evidence may entail
credibility or reliability findings, while constructions
based solely on the patent document and prosecution
history would receive de novo review.
    The proponents of a hybrid form of appellate review
argue that this approach comports with the Court’s posi-
tion in Markman II, yet respects the traditional roles of
trial and appellate courts. Thus it is proposed that the
standard of review of claim construction should vary with
the source and purpose of the evidence, drawing analogy
to review of the determination of obviousness under 35
U.S.C. §103. See Brief of Amicus Curiae American Bar
Association at 12 (“it is well settled that Rule 52(a) gov-
erns appellate review of the factual inquiries underlying
the ultimate legal issue of obviousness”).
The third view
     The third view, supported by some amici curiae, is
that Cybor is both reasonable and correct in view of the
Court’s rulings in Markman II. These proponents stress
the Court’s statements that claim construction is a “pure-
ly legal” matter, 517 U.S. at 391, and that “the interpreta-
tion of a so-called patent claim . . . is a matter of law,” id.
at 372. They argue that de novo review of the scope and
meaning of patent claims conforms to the rule that ap-
plies in all areas of law, that “interpreting a set of legal
words . . . in order to determine their basic intent” is a
“purely legal matter.” Buford v. United States, 532 U.S.
59, 65 (2001). They state that sufficient reason has not
been shown to change this established and effective
precedent in patent cases.
    In Markman II the Court placed claim construction in
historical context, quoting Professor Robinson’s treatise:
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                  13


       The duty of interpreting letters-patent has
   been committed to the courts. A patent is a legal
   instrument, to be construed, like other legal in-
   struments, according to its tenor . . . . Where
   technical terms are used, or where the qualities of
   substances or operations mentioned or any similar
   data necessary to the comprehension of the lan-
   guage of the patent are unknown to the judge, the
   testimony of witnesses may be received upon
   these subjects, and any other means of infor-
   mation be employed. But in the actual interpreta-
   tion of the patent the court proceeds upon its own
   responsibility, as an arbiter of the law, giving to
   the patent its true and final character and force.
517 U.S. at 388 (quoting 2 W. Robinson, Law of Patents
§732, pp. 481–83 (1890)) (emphasis the Court’s). Propo-
nents of retaining the Cybor standard point to the Court’s
emphasis that the judge is responsible for “the actual
interpretation of the patent.” Id. These proponents also
point to the Court’s citation to Miller v. Fenton, 474 U.S.
104 (1985) in support of the Court’s ruling in Markman II
that:
       [W]hen an issue “falls somewhere between a
   pristine legal standard and a simple historical
   fact, the fact/law distinction at times has turned
   on a determination that, as a matter of the sound
   administration of justice, one judicial actor is bet-
   ter positioned than another to decide the issue in
   question.” So it turns out here, for judges, not ju-
   ries, are the better suited to find the acquired
   meaning of patent terms.
Markman II, 517 U.S. at 388 (quoting Miller, 474 U.S. at
114). These proponents argue that Miller confirms that
the Court in Markman II intended to decide—and effec-
tively did decide—both the judge/jury question and the
14                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


fact/law question, as well as the related question concern-
ing appellate review.
    The Court’s reliance on Miller in Markman II illus-
trates the Court’s recourse to general jurisprudence and
practical considerations, suitably applied, in resolving
patent issues. Proponents of adherence to Cybor point out
that Miller reiterated the Court’s recognition in Pullman-
Standard that no principle will “‘unerringly distinguish a
factual finding from a legal conclusion.’” Miller, 474 U.S.
at 113 (quoting Pullman-Standard, 456 U.S. at 288).
Proponents apply that observation to criticize departure
from Cybor that would add, to the already complex laws of
claim construction, a new and uncertain and contentious
inquiry into which aspects of a particular construction fall
on which side of the fact-law line. These proponents state
that Cybor is not subject to these difficulties, and that
there is not sufficient reason to impose this new area of
dispute and peripheral litigation upon the trial and
appeal of patent cases.
     The proponents of stare decisis point to the courts’ and
patent community’s fifteen years of experience with
Cybor, and argue that this experience supports retention
of the Cybor principle. Emphasizing the potential multi-
case and multi-forum litigation of patents on today’s
technologies, they argue that it is particularly important
that this court be able to resolve claim construction defin-
itively as a matter of precedent, rather than allow differ-
ing trial court constructions of the same patent, as may
result from deferential review of close questions. As the
Court observed in Markman II, “treating interpretive
issues as purely legal will promote (though it will not
guarantee) intrajurisdictional certainty through the
application of stare decisis on those questions not yet
subject to interjurisdictional uniformity under the author-
ity of the single appeals court.” 517 U.S. at 391.
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                 15


    Thus it is argued that the meaning and scope of a pa-
tent claim, which sets the boundaries of an exclusionary
right good against the world at large, rather than only for
parties to a voluntary transaction or only for the plaintiff
and defendant in a particular case, should be construed
based on publicly available materials in the record, and
resolved for uniform application throughout the nation, as
a matter of law. No party or amicus disputed that the
only way to achieve uniform construction of the same
claim, a goal recognized in Markman II, is by de novo
appellate construction of the claim as a matter of law.
There is no dispute as to the importance of national
uniformity and finality of claim construction, for it is not
unusual for different district courts to litigate the same
patent against different parties and different assertions of
infringement.
     In sum, these proponents argue that the Cybor stand-
ard of review of claim construction reasonably and appro-
priately implements the Court’s ruling in Markman II,
and urge this court to stand by Cybor and its fifteen years
of experience. Proponents of stability through the princi-
ples of stare decisis stress that consistency of legal analy-
sis and reliability of judicial process are foundations of not
only legal systems generally, but also of the technological
advance and industrial commitment that are goals of the
patent system. See Brief of Amici Curiae Cisco et al. at 15
(“Competing and inconsistent interpretations of patent
claims obscure the boundaries of patents and deeply
undermine their important notice function, inevitably
resulting in more—rather than less—litigation.”); id. at
19 (“Clear scope is important to all potential market
entrants. This kind of horizontal certainty is important to
the entire industry.”).
     The criticism of Cybor is not based on any demonstra-
tion that de novo claim construction is likely to be incor-
16                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


rect, but rather on concerns for judicial roles and relation-
ships. We do not ignore these important concerns. How-
ever, as proponents of stare decisis point out, Cybor is
narrowly focused on the threshold construction of a legal
document, and does not affect the traditional deference to
district court findings of infringement or validity or
damages or any other question of fact in patent litigation.
The proponents remind us that Cybor was adopted in
implementation of the Markman decisions of this court
and the Supreme Court, and is in accord with these
rulings on the nature of the patent grant and the judicial
obligation for correct determination of the legal scope of
the patent grant.
    Thus it is urged that the Cybor standard should not
now be abandoned for a more costly and litigious stand-
ard, with diminished stability of procedure and dimin-
ished reliability of outcome, and no greater likelihood of
correctness of result. These proponents point out that
those who would change Cybor’s system of plenary review
of claim construction have not shown any benefit or
advantage to the law or those served by the law. Thus it
is argued that the values of stare decisis counsel against
overturning Cybor.
                           II
                      STARE DECISIS
    The question now before this en banc court is not the
same question that was before the en banc court in 1998
when Cybor was decided. The question now is not wheth-
er to adopt a de novo standard of review of claim construc-
tion, but whether to change that standard adopted fifteen
years ago and applied in many hundreds of decisions.
There has been extensive experience of Cybor in action, in
the district court and on appeal. “Claim construction” has
become the gateway issue in patent litigation, often
decided in preliminary proceedings before trial and before
LIGHTING BALLAST   v. PHILIPS ELECTRONICS               17


discovery, and often subject to immediate appeal on
summary judgment or injunction grounds. Such experi-
ence enriches the principle that courts will “stand by
things decided” so that prior rulings may be relied upon.
     Stare decisis is of “fundamental importance to the rule
of law.” Hilton v. S. Carolina Pub. Ry. Comm’n, 502 U.S.
197, 202 (1991) (quoting Welch v. Texas Dep’t of Highways
& Pub. Transp., 483 U.S. 468, 494 (1987)). The doctrine
of stare decisis enhances predictability and efficiency in
dispute resolution and legal proceedings, by enabling and
fostering reliance on prior rulings. CSX Transp. Inc. v.
McBride, 131 S. Ct. 2630, 2641 (2011). By providing
stability of law that has been decided, stare decisis is the
foundation of a nation governed by law. The Supreme
Court has said: “we will not depart from the doctrine of
stare decisis without some compelling justification.”
Hilton, 502 U.S. at 202 (citing Arizona v. Rumsey, 467
U.S. 203, 212 (1984)); see Dickerson v. United States, 530
U.S. 428, 443 (2000) (“special justification” is needed to
overrule precedent).
    Stability in procedural as well as substantive law, on
which the public and the courts can rely, guards against
the expenditure of time and resources on aspects that
have been resolved. These values come to the fore when a
court undertakes to reexamine its own precedent, for stare
decisis implements the “prudential and pragmatic consid-
erations designed to test the consistency of overruling a
prior decision with the ideal of the rule of law, and to
gauge the respective costs of reaffirming and overruling a
prior case.” Planned Parenthood of S.E. Pa. v. Casey, 505
U.S. 833, 854 (1992). The principles and policies of stare
decisis operate with full force where, as here, the en banc
court is considering overturning its own en banc prece-
dent.
18                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


    The presumption that a court will adhere to its prior
rulings has “‘special force’” for precedents that resolve
non-constitutional issues, for “‘Congress remains free to
alter what we have done.’” J.R. Sand & Gravel Co. v.
United States, 552 U.S. 130, 139 (2008) (quoting Patterson
v. McLean Credit Union, 491 U.S. 164, 172–73 (1989)). In
Patterson the Court observed that the same issue had
previously divided the Court and that “[s]ome Members of
this Court believe that [the precedent] was decided incor-
rectly”; the Court discussed the principles of stare decisis,
and concluded that “no special justification has been
shown for overruling” the prior decision, for neither “the
growth of judicial doctrine or further action taken by
Congress. . . . have removed or weakened the conceptual
underpinnings from the prior decision.” 491 U.S. at
171-173. The Court observed that no “later law has
rendered the decision irreconcilable with competing legal
doctrines or policies.” Id. at 173.
    In Hohn v. United States, 524 U.S. 236, 253 (1998) the
Court discussed its precedent in light of stare decisis, and
stated that “[o]nce we have decided to reconsider a partic-
ular rule, however, we would be remiss if we did not
consider the consistency with which it has been applied in
practice.” In Global-Tech Appliances, Inc. v. SEB S.A.,
131 S. Ct. 2060, 2067-68 (2011) the Court observed that
although its prior decision on the same issue was “badly
fractured,” the majority holding “has become a fixture in
the law,” warranting application of the doctrine of stare
decisis.
     The purposes of consistency and stability that under-
lie stare decisis led to the formation of the Federal Circuit,
now thirty years past, to provide consistency and stability
to the patent law: “The central purpose is to reduce the
widespread lack of uniformity and uncertainty of legal
doctrine that exist in the administration of patent law,”
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                19


H.R. REP. 97–312, at 23 (1981), in view of the importance
of technology-based advance to the nation’s economy, id.;
S. REP. 97–275, at 6 (1981) (same). Legal doctrine in
patent law starts with the construction of patent claims,
for the claims measure the legal rights provided by the
patent.
     In the Federal Circuit decision that led to the Su-
preme Court’s Markman II ruling, this court explained
that reviewing claim construction as a matter of law
assures “a true and consistent scope of the claims.”
Markman I, 52 F.3d at 979. The Court did not adjust or
criticize that position, which forms the foundation of
Cybor. Cybor, in carrying forward Markman I in light of
Markman II, embodies the view that de novo review will
“help institute a simplified and clarified method by which
both trial and appellate courts address claim construction
issues.” Cybor, 138 F.3d at 1463 (Plager, J., concurring).
    We do not ignore that neither Cybor nor the Markman
decisions were free of contention, then as now. As we
undertake this review of Cybor, we recognize that stare
decisis is not an “inexorable command,” Agostini v. Felton,
521 U.S. 203, 235 (1997). Thus we have considered
whether there are sound reasons for this court now to
depart from this precedent. We proceed with the guid-
ance of history, experience, and the many amici curiae,
while retaining awareness that to overturn an en banc
ruling that has had long and wide application, there must
be more than controversy about the prior rule. See Wat-
son v. United States, 552 U.S. 74, 82 (2007) (“A difference
of opinion within the Court . . . does not keep the door
open for another try . . . .”). As observed in Morrow v.
Balaski, 719 F.3d 160, 181 (3d Cir. 2013) (Smith, J.,
concurring), “the very point of stare decisis is to forbid us
from revisiting a debate every time there are reasonable
arguments to be made on both sides.”
20                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


    However, departure from precedent may be appropri-
ate when “subsequent cases have undermined [its] doctri-
nal underpinnings,” Dickerson, 530 U.S. at 443; or when
the precedent has proved “unworkable,” J.R. Sand &
Gravel Co., 552 U.S. at 139; or when “a considerable body
of new experience” requires changing the law, Pearson v.
Callahan, 555 U.S. 224, 234 (2009).
    Stare decisis embraces procedural as well as substan-
tive precedent. Vasquez v. Hillery, 474 U.S. 254, 266
(1986) (considering whether procedures have so far devel-
oped as to have left the old rule “outdated, ill-founded,
unworkable, or otherwise legitimately vulnerable to
serious reconsideration”); Swift & Co. v. Wickham, 382
U.S. 111, 116 (1965) (overruling procedural precedent
where “unworkable in practice,” among other problems).
Procedures in the litigation-prone arena of patent rights
can affect the cost, time, and uncertainty of litigation, and
in turn affect economic activity founded on the presence
or absence of enforceable patents. Courts should be
“cautious before adopting changes that disrupt the settled
expectations of the inventing community.” Festo Corp. v.
Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 739
(2002).
    Applying these premises, we have reviewed the argu-
ments for changing the Cybor procedure of de novo review
of claim construction. First, we have looked for post-
Cybor developments, whether from the Supreme Court,
from Congress, or from this court, that may have under-
mined the reasoning of Cybor. None has been found, or
brought to our attention. There has been no legislative
adjustment of the Cybor procedure, despite extensive
patent-related legislative activity during the entire period
of Cybor’s existence.
   We have looked for some demonstration that Cybor
has proved unworkable. No proponent of change has
LIGHTING BALLAST   v. PHILIPS ELECTRONICS               21


shown that de novo review of claim construction is un-
workable—nor could they, after fifteen years of experience
of ready workability. Nor has anyone shown that Cybor
has increased the burdens on the courts or litigants
conducting claim construction.
    To the contrary, reversing Cybor or modifying it to in-
troduce a fact/law distinction has a high potential to
diminish workability and increase burdens by adding a
new and uncertain inquiry, not only on appeal but also in
the trial tribunal. No consensus has emerged as to how to
adjust Cybor to resolve its perceived flaws. Despite
probing questioning at the en banc hearing, and despite
the extensive amicus curiae participation, there is no
agreement on a preferable new mechanism of appellate
review of claim construction; there is no analysis of how
deference would be applied to the diversity of old and new
technologies and modes of claiming, no clear exposition of
fact or law as could be applicable to the millions of unex-
pired patents, each on a different new technologic ad-
vance. As will be discussed, no one, including the dissent,
proposes a workable replacement standard for Cybor, no
workable delineation of what constitutes fact and what
constitutes law.
    Disentangling arguably factual aspects, some in dis-
pute and some not, some the subject of expert or other
testimony and some not, some elaborated by documentary
evidence and some not, some construed by the district
court and some not, some related to issues to be decided
by a jury and some not—and further disentangling factual
aspects from the application of law to fact—is a task ripe
for lengthy peripheral litigation. We are not persuaded
that we ought to overturn the en banc Cybor decision and
replace its clear de novo standard with an amorphous
standard that places a new, cumbersome, and costly
process at the gate, to engender threshold litigation over
22                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


whether there was or was not a fact at issue. The princi-
ples of stare decisis counsel against such an unnecessary
change.
     No critic of Cybor has provided any analysis of specific
claims or cases to show, or even to suggest, that deferen-
tial appellate review is more likely to achieve the correct
claim construction. The principles of stare decisis counsel
against overturning precedent when there is no evidence
of unworkability and no clearly better resolution. The
amici curiae agreed that modification of Cybor is unlikely
to change many results, even if it could be defined well
(which it has not been, by any amicus or by our colleagues
in dissent).
     Claim construction is a legal statement of the scope of
the patent right; it does not turn on witness credibility,
but on the content of the patent documents. The court
may indeed benefit from explanation of the technology
and the instruction of treatises, but the elaboration of
experts or tutorial explanation of technical subject matter
does not convert patent claim construction into a question
of fact. The type of evidence that may assist a lay judge
in determining what a technical term meant to one of skill
in the art does not transform that meaning from a ques-
tion of law into a question of fact. Reference to technical
understanding and usage at the time of enactment does
not convert statutory interpretation from law to fact. See,
e.g., Corning Glass Works v. Brennan, 417 U.S. 188, 202
(1974) (applying “the language of industrial relations” to
statutory interpretation).
    Courts routinely look to dictionaries and treatises to
determine the meaning of a statute at the time it was
written. See, e.g., Sandifer v. U.S. Steel Corp., 134 S. Ct.
870 (2014) (looking to dictionaries to determine the mean-
ing of “changing clothes” in the Fair Labor Standards Act
at the time of enactment); Comm’r v. Soliman, 506 U.S.
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                23


168 (1993) (interpreting the tax code by looking to dic-
tionary definitions at the time of enactment); Chapman v.
United States, 500 U.S. 453 (1991) (using dictionaries to
ascertain the ordinary meaning of “mixture” in the drug
statute).
    Similarly, experts in the science or technology may
assist the court in understanding the meaning and usage
of a claim term, but this does not morph the question into
one of fact. Cf. United States v. Stone & Downer Co., 274
U.S. 225 (1927) (relying on expert testimony on the mean-
ing of the tariff term “clothing wool” in the custom of the
trade). The Court stated in Markman II:
   in theory there could be a case in which a simple
   credibility judgment would suffice to choose be-
   tween experts whose testimony was equally con-
   sistent with a patent’s internal logic. But our own
   experience with document construction leaves us
   doubtful that trial courts will run into many cases
   like that. In the main, we expect, any credibility
   determinations will be subsumed within the nec-
   essarily sophisticated analysis of the whole docu-
   ment, required by the standard construction rule
   that a term can be defined only in a way that
   comports with the instrument as a whole.
517 U.S. at 389. This expectation has proven accurate.
The presentation of expert testimony on the meaning of a
claim term does not transform the question from one of
law to one of fact.
    We have carefully considered the arguments for dis-
carding or modifying Cybor, and conclude that they do not
justify departing from the now well-established principles
and procedures. Under any standard of review consistent
with Markman II, most issues of claim construction are
indisputably matters of law, and would receive de novo
24                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


review. Even the critics of Cybor agree that any change
would affect only a small number of claim construction
disputes. Statements at the en banc hearing are edifying;
e.g., Tr. at 1:14:10–1:14:35 (Appellant) (“This court could,
in whatever it does with Cybor, make very clear that this
battle of competing experts is rarely productive, rarely
going to influence claim construction. . . . If you said to
me, why doesn’t stare decisis carry the day? I don’t have a
good answer to that.”); id. at 55:15–55:20 (United States)
(“this court’s law on claim construction requires very little
modification”); id. at 1:06:50–1:07:30 (United States)
(whether a term has special meaning in the art could be
“meaningless ultimately” if inconsistent with the intrinsic
record).
    In response to a question at the hearing, amicus curi-
ae United States could not identify any case that would
have come out differently under the modified (hybrid)
standard of review it proposed. Tr. at 1:07:30–1:08:00.
Certainly stare decisis counsels against overturning en
banc precedent where doing so would change our known,
workable de novo standard to an undefined alternative,
sure to engender peripheral litigation, and which most
agree could affect the outcome of very few, if any cases.
See Pearson, 555 U.S. at 236–37 (criticizing precedent
that “sometimes results in a substantial expenditure of
scarce judicial resources on difficult questions that have
no effect on the outcome of the case”).
    Claim construction is often a preliminary proceeding
in the district court, before trial of infringement, validity,
damages, etc. At the threshold, the court establishes the
metes and bounds of the claims that define the patent
right. The questions of claim construction are not ques-
tions of weight of evidence or credibility of witnesses, but
of the claim scope as set forth in the patent documents.
LIGHTING BALLAST   v. PHILIPS ELECTRONICS               25


    Claim construction is the interpretation of a legal
document that establishes a property right that applies
throughout the nation. The question under review is
whether this court, of nation-wide jurisdiction, should
continue to review claim construction de novo with na-
tional effect, or whether to change to a system whereby a
district court’s claim construction is reviewed on the
deferential standard appropriate to findings of fact, with
or without some sort of hybrid deference to the ultimate
determination. The insistence of some amici curiae that
some form of deferential review is required as well as
superior, is not only contrary to the Markman holdings,
but to the experience of fifteen years of Cybor.
    In the increasingly frequent situation where the same
patent is litigated in different forums against different
defendants, differing district court rulings on close ques-
tions of claim construction could well warrant affirmance
on deferential review. Because differing claim construc-
tions can lead to different results for infringement and
validity, the possibility of disparate district court con-
structions unravels the “uniformity in the treatment of a
given patent” that the Court sought to achieve in Mark-
man II. 517 U.S. at 390. It would restore the forum
shopping that the Federal Circuit was created to avoid.
Just as the Court in Markman II counted such conse-
quences as negatives that its ruling overcame, they count
as negatives in the stare decisis analysis.
    The question that this court has now reconsidered is
whether we should continue to review claim construction
as a whole and de novo on the record, or whether we
should change to a different system that at best would
require us to identify any factual aspects and how the
trial judge decided them, and review any found or inferred
facts not for correctness but on a deferential standard,
with or without also giving deferential review to the
26                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


ultimate determination of the meaning of the claims. We
conclude that such changed procedure is not superior to
the existing posture of plenary review of claim construc-
tion.
    Over these fifteen years this court has applied Cybor
to diverse subject matter, and the body of precedent has
grown large. Deferential review does not promise either
improved consistency or increased clarity. We have been
offered no argument of public policy, or changed circum-
stances, or unworkability or intolerability, or any other
justification for changing the Cybor methodology and
abandoning de novo review of claim construction.
    The proponents of overruling Cybor have not met the
demanding standards of the doctrine of stare decisis.
They have not shown that Cybor is inconsistent with any
law or precedent, or that greater deference will produce
any greater public or private benefit. We conclude that
there is neither “grave necessity” nor “special justifica-
tion” for departing from Cybor.
                         III
                REMARKS ON THE DISSENT
     Our colleagues in dissent offer a few arguments that
warrant response. First, referring to “the materials
submitted to the court,” the dissent states that “a sub-
stantial proportion of the legal community” believes that
Cybor was “wrongly decided.” Diss. at 6. The materials
tell a different tale.
    As listed ante, at n.2, thirty-eight organizations and
individuals filed twenty-one amicus briefs. Contrary to
the dissent’s statements, all of the technology industries
that offered advice to the court, urge retention of Cybor’s
standard. These amici curiae include the largest technol-
ogy companies in the nation, all involved with the system
of patents, all frequent patent litigants both as plaintiffs
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                27


and as defendants—unlike all of the other amici. 4 The
dissent dismisses these voices as merely “some amici” who
support retention of Cybor, Diss. at 6, and offers no re-
sponse to their concerns for stability, national uniformity,
and predictability in claim construction.
    The dissent appears unconcerned that the major in-
dustrial amici urge retention of the Cybor standard, and
instead announces that “no one in the legal community—
except perhaps the members of the majority—has come to
believe that either the wisdom or vitality of Cybor is
settled,” Diss. at 6. This conclusion is curious. For exam-
ple, the amicus brief of Google, Amazon, Hewlett-Packard,
Red Hat and Yahoo! states that departing from Cybor
would “make worse” the uncertainty of claim construction:
       [T]he root causes of uncertainty in claim con-
   struction are vaguely drafted claims and contra-
   dictory claim-construction methodologies, not
   appellate review. Deference would not ameliorate
   those causes of uncertainty; it would make them
   worse.
       ***
       [T]reating claim construction as a factual
   question subject to clear-error review would only
   aggravate the uncertainty and cost issues plagu-
   ing our patent-litigation system.


   4    Amazon.com, Inc., Cisco Systems, Inc., Dell Inc.,
EMC Corporation, Google Inc., Hewlett-Packard Co., Intel
Corporation, Microsoft Corporation, SAP America Inc.,
Red Hat, Inc., and Yahoo! Inc. Other amici in support of
preserving the full Cybor standard are the Austin Intel-
lectual Property Lawyers Association and the Intellectual
Property Institute at the William Mitchell College of Law.
28                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


Brief of Amicus Curiae Google et al. at 4, 5.
     The industrial amici also respond to the argument,
pressed by the dissenters, that treating claim construction
as a matter of law negates settlement and increases
litigation cost. Diss. at 35. These litigants advise that
the contrary is true:
         [C]lassifying claim construction as being at
     least partly factual would make patent litigation
     even more costly by discouraging courts from re-
     solving claim construction disputes at the outset.
     Early claim construction is essential to permit the
     parties to file summary judgment motions, or to
     engage in informed settlement discussions, before
     they have to incur potentially unnecessary discov-
     ery and other pre-trial costs—costs that force
     many defendants to settle even meritless cases
     solely because the exorbitant cost of litigating a
     case would exceed the settlement amount de-
     manded by the plaintiff.
Google et al. Br. at 4-5. Even Appellant’s counsel at oral
argument contradicted the cost-of-litigation and settle-
ment arguments:
         A lot of commentators have said Cybor is pre-
     venting settlements: I don’t believe that. I settle
     cases all the time. No one has ever focused pri-
     marily or even significantly on the standard of re-
     view on appeal. They’re focused on the jury.
     They’re focused on the cost of litigation. So a lot
     of what’s been put up as reasons to change Cybor I
     don’t think are there.
Tr. 1:14:40-1:15:05.
    In the brief filed by Cisco, Dell, EMC, Intel, SAP, and
the SAS Institute, these amici curiae suggest that the
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                     29


proponents of overturning Cybor incorrectly conflate
concepts of uncertainty with appellate reversal rates.
These amici explain that any possible uncertainty of
affirmance on appeal is not the issue in claim construc-
tion; rather, the issue is how to generate accuracy and
uniformity in claim construction, that is, how to construe
claims correctly and predictably.
         Clear scope is important to all potential mar-
    ket entrants. This kind of horizontal certainty is
    important to the entire industry. By contrast, the
    concern that de novo review increases the “dura-
    tion” of a single patent litigation until a final deci-
    sion is reached in that particular case (Cybor, 138
    F.3d at 1476 (Rader, J., dissenting))—what might
    be called vertical uncertainty—matters only in the
    small fraction of cases that reach an appeal. Ver-
    tical uncertainty is more visible than horizontal
    uncertainty, but, as often is the case, here it is the
    unseen effects that are greater. Cf. Frédéric Bas-
    tiat, What Is Seen and What Is Not Seen (1848),
    available     at     http://www.econlib.org/library/-
    Bastiat/basEss1.html.
        For this reason, it is not merely the overarch-
    ing principles of claim construction, but their ap-
    plication, that must be consistent. In claim
    construction as elsewhere, “the relevant legal
    principle can be given meaning only through its
    application to the particular circumstances of a
    case.” Miller, 474 U.S. at 114.
Brief of Amicus Curiae Cisco et al. at 19.
    The Cisco amici emphasize the Supreme Court’s
recognition of “the importance of uniformity” in Markman
II, 517 U.S. at 390, and stress that treating claim con-
30                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


struction issues as “purely legal,” id. at 391, enables
appellate review to supply that uniformity:
         Federal Circuit review, and in particular this
     Court’s application of stare decisis, is critical to
     such uniformity. As the Supreme Court ex-
     plained, “treating interpretive issues as purely le-
     gal” will allow stare decisis to be applied to those
     interpretive questions and thus promote uniformi-
     ty among decisions of this Court (so-called “intra-
     jurisdictional certainty”).
Cisco et al. Br. at 5 (citing and quoting Markman II, 517
U.S. at 391). These amici also discuss the “hybrid” pro-
posal of some theorists, and state:
         “treating interpretive issues as purely legal”—
     not as a mixed question—is the proper approach.
Id. at 5 (quoting Markman II, 517 U.S. at 391).
    Amicus Microsoft discusses another aspect of the Cy-
bor treatment of claim construction, advising that de novo
review
         works well in practice because it allows the
     parties to address questions concerning claim
     scope in pre-trial hearings well in advance of the
     actual trial. Having a jury decide these re-
     designated factual matters could eliminate the
     current practice of pre-trial Markman hearings.
     This would exacerbate the expense and uncertain-
     ty in patent litigation and create new opportuni-
     ties for forum shopping.
Brief of Amicus Curiae Microsoft at 3.
    In sum, the amici curiae record of the nation’s major
innovators is contrary to the dissent’s representation that
“no one in the legal community—except perhaps the
LIGHTING BALLAST   v. PHILIPS ELECTRONICS               31


members of the majority—has come to believe that either
the wisdom or vitality of Cybor is settled.” Diss. at 6. The
amici curiae record is contrary to the dissent’s pro-
nouncement that “the interests of stability and predicta-
bilty are disserved” by Cybor’s access to final, uniform,
national claim construction. Diss. at 29. The nation’s
major innovators do not agree with the criticisms of
Cybor, and so advised the court. These amici direct the
court to the pragmatic value of Cybor as they have experi-
enced it, and urge retention of that value.
    Rather than respond to the concerns of the nation’s
technology industries, the dissent chastizes certain judges
of this court for not “acting on their long-term convic-
tions.” Diss. at 2. While it is comforting to know that our
golden words of the past are not forgotten, those of us
with the majority today who have questioned aspects of
Cybor in the past, now decide this case on the record of
the present and with an eye to the future. The dissent
would discard the experience of the past fifteen years.
However, the court is not now deciding whether to adopt a
de novo standard in 1998. Today we decide whether to
cast aside the standard that has been in place for fifteen
years.
    The dissent offers no superior alternative to de novo
review, nor any workable standard for distinguishing
between legal and factual components of claim construc-
tion. The dissent does not appear to adopt the proposal of
several amici that appellate deference should depend on
whether the district court relied on intrinsic or extrinsic
evidence in construing a claim term. It is surely doubtful
that such a distinction controls whether claim construc-
tion is fact or law. See Phillips v. AWH Corp., 415 F.3d
1303, 1317 (Fed. Cir. 2005) (en banc) (discussing sources
of evidence in claim construction, and stating “while
extrinsic evidence ‘can shed useful light on the relevant
32                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


art,’ we have explained that it is ‘less significant than the
intrinsic record in determining ‘the legally operative
meaning of claim language’”) (citing cases). We have
come upon no rationale for denominating an issue of claim
construction as one of fact or law depending on the source
of the information considered by the judge.
    The dissent seems to embrace (then expand upon) the
“historical fact” notion proposed by Appellant, who states
that the meaning a person of ordinary skill in the art
would give a term at the time of the filing of the patent
application ought to be treated as a question of fact. This
is not a question of fact; it is the very inquiry which
determines the claim construction in nearly all cases.
Claim terms are given their ordinary meaning to one of
skill in the art, unless the patent documents show that
the patentee departed from that meaning. See Phillips,
415 F.3d at 1314; Thorner v. Sony Computer Entm’t Am.,
LLC, 669 F.3d 1362, 1365 (Fed. Cir. 2012). Treating the
ordinary meaning to a skilled artisan as requiring defer-
ence would mean deference on the controlling question of
claim construction in nearly every case. All the more so
with the dissent’s proposed treatment of still additional
issues, such as prosecution disclaimer, as warranting
deference. Diss. at 42.
    Under the dissent’s approach, and even under the
“historical fact” approach, deference would become of
central significance in controlling the determination of
claim construction, and hence of patent scope. The conse-
quence would be heightened forum-shopping and the
inability of the judicial system to arrive at a uniform,
settled meaning for a patent’s scope. Those problems are
grave ones given the increasingly common situation of
multiple cases involving the same patent.
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                   33


    The dissenters do not explain why they choose to
abandon the benefits foreseen by the Court in Markman
II, that “treating interpretive issues as purely legal”
would have benefits of “intrajurisdictional certainty.” 517
U.S. at 391. Nor have they successfully explained away
the analysis in Miller v. Fenton, 474 U.S. at 113–14, that:
         [T]he practical truth that the decision to label
   an issue a “question of law,” a “question of fact,” or
   a “mixed question of law and fact” is sometimes as
   much a matter of allocation as it is of analysis
   . . . . [T]he fact/law distinction at times has turned
   on a determination that, as a matter of the sound
   administration of justice, one judicial actor is bet-
   ter positioned than another to decide the issue in
   question.
(cited in Markman II, 517 U.S. at 388). The Court in
Miller explained that the fact/law distinction is not immu-
table, and may invoke “the sound administration of
justice,” id. at 114, leading to a similar acknowledgement
in the Markman II ruling that claim construction is “a
matter of law reserved entirely for the court.” 517 U.S at
372.
    In addition, the dissent downplays the gravity of over-
turning a previous en banc court in the absence of inter-
vening Supreme Court or legislative action. Of the
several decisions of the Federal Circuit that the dissent
cites as setting a pattern of overturning precedent, all
involve en banc review of panel precedents, with the
arguable exception of Nobelpharma AB v. Implant Inno-
vations, Inc., 141 F.3d 1059, 1068 & n.5 (Fed. Cir. 1998)
(en banc in relevant part), where the court clarified that
this court’s law would govern the question of pa-
tent/antitrust immunity.
34                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


     The major thrust of the dissent is that Federal Rule
52(a)(6) requires deferential review of district court deci-
sions. But Rule 52(a) does not answer the question here.
Rule 52(a) prescribes the standard of review of questions
of fact, but courts must look outside the Rule to decide if a
question is properly characterized as one of fact. As the
Court stated in Pullman-Standard, 456 U.S. at 288, “Rule
52(a) does not furnish particular guidance with respect to
distinguishing law from fact. Nor do we yet know of any
other rule or principle that will unerringly distinguish a
factual finding from a legal conclusion.” The dissent’s
theory that Rule 52(a) demands abandonment of de novo
review of claim construction is a simplistic disregard of
the Markman II guidance that “treating interpretive
issues as purely legal will promote (though it will not
guarantee) intrajurisdictional certainty.” 517 U.S. at 391.
    The dissent argues that de novo review produces a
high reversal rate, although it is established that this is
no longer true. The reversal rate indeed was a matter of
concern, for in the early years of Cybor, this court’s prom-
ulgation of claim construction law led to a higher rate of
appellate adjustment. However, as consistency evolved
and experience grew, rates of appellate reversal for claim
construction came to match the norm for other grounds.
We observe that every amicus brief that complains about
high reversal rates relies on data that are seven to ten or
more years old, while the author of a recent study writes
in his amicus brief that the data “document a significant
drop in the claim construction reversal rate” since 2005,
Brief of Amicus Curiae Professor Peter Menell at 15, and
explains in his study that “[n]ow the reversal rate for
claim construction appeals is much closer to that of other
patent-related issues.” J. Jonas Anderson & Peter S.
Menell, Informal Deference: An Historical, Empirical, and
Normative Analysis of Patent Claim Construction, 108
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                35


Nw. U. L. Rev. (forthcoming), Sept. 9, 2013 manuscript at
37.
     Our colleagues in dissent, citing the obsolete data, ar-
gue that the de novo standard “adds considerable uncer-
tainty and expense to patent litigation,” Diss. at 4, stating
that this standard increases appeals, discourages settle-
ment, and increases the length and cost of litigation. No
evidence of this effect is offered, and all of the amici
curiae who are frequent litigants state the contrary
position. The data published by the Administrative Office
of the United States Courts point the other way. These
data show a long, noticeable decline in the percentage of
district court patent cases that are appealed, belying the
argument that appeals have increased. The following
data are from the Annual Reports of the Administrative
Office for the years 1994 to 2013. The graph shows the
ratio, as a percentage, of the number of patent appeals
filed per year (Report Table B-8), against the number of
district court patent cases filed in that year (Report Table
C-2):
36                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


    The Annual Reports also show the trend in the
percentage of patent cases that proceed to trial in the
district courts. The data from Table C-4 in the Reports
show the percentage declining from 5.9% in 1994 to 2.8%
in 2013:




The data do not support the dissent’s theory that Cybor
has increased patent litigation and inhibited settlements.
In contrast, the industrial amici curiae advise the court
that the Cybor review procedure assists in resolving
litigation before full trial or extensive discovery, for it
often leads to the grant of summary judgment and an
immediate appeal. These amici stress that settlement is
facilitated by final resolution of the scope of the claims.
They also point out that if the claim construction is defini-
tively resolved, any ensuing trial is on the final claim
construction. The dissent does not comment on these
values.
                        CONCLUSION
    We have again considered the standard of review of
district court claim construction rulings, in light of expe-
LIGHTING BALLAST   v. PHILIPS ELECTRONICS               37


rience with the Cybor standard. The ever-enlarging
importance of technology-based industry in the economy
has reinforced the need for an optimum patent system.
     On thorough review, we are not persuaded that dis-
carding de novo review would produce a better or more
reliable or more accurate or more just determination of
patent claim scope. Those who urge change in the Cybor
standard have identified no pattern of error, no indict-
ment of inferior results. No ground has been shown for
departing from the principles of stare decisis. Review of
claim construction as a matter of law has demonstrated
its feasibility, experience has enlarged its values, and no
clearly better alternative has been proposed. There has
arisen no intervening precedent, no contrary legislation,
no shift in public policy, no unworkability of the standard.
    We conclude that the criteria are not met for overrul-
ing or modifying the Cybor standard of de novo review of
claim construction as a matter of law.
          PANEL DECISION REINSTATED
   No costs.
  United States Court of Appeals
      for the Federal Circuit
                 ______________________

       LIGHTING BALLAST CONTROL LLC,
               Plaintiff-Appellee,


                            v.


    PHILIPS ELECTRONICS NORTH AMERICA
               CORPORATION,
                 Defendant,


                          AND


  UNIVERSAL LIGHTING TECHNOLOGIES, INC.,
             Defendant-Appellant.
                 ______________________

                       2012-1014
                 ______________________

   Appeal from the United States District Court for the
Northern District of Texas in Case No. 09-CV-0029, Judge
Reed O’Connor.
                 ______________________

LOURIE, Circuit Judge, concurring.
    I fully agree with the majority opinion and join it. I
write separately to note what I believe are additional
reasons why retaining Cybor is wise.
2                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


    First and foremost is that the Supreme Court has
held that claim construction is a question for the court
rather than the jury. Thus, for us to appear to be cutting
back from that holding by giving formal deference on so-
called fact-like questions, which normally would go to the
jury, to the district court judge, would seem to me to be an
attempt to partially retreat from the Court’s holding,
which is unwise.
    We have held that claim construction is a question of
law, going only minimally beyond the Court’s explicit
holding that it is only a question for the court. Cybor
Corp. v. FAS Techs., Inc., 138 F.3d 1448, 1454–55 (Fed.
Cir. 1998) (en banc). The Court’s holding, including its
statement that it is a “mongrel” question, does not en-
courage fractionation of the process, making part of it
subject to de novo review and part clearly erroneous
review. The Court in Markman stated that construction
of terms of art should be ceded to the judge “notwith-
standing its evidentiary underpinnings.” The “notwith-
standing” applies to any factual as well as legal aspects of
claim construction. Evidentiary underpinnings do not
lean toward a clearly erroneous standard any more than
they do to the jury.
    Equally important, one of the purposes of Congress in
creating our court was to achieve uniformity in the patent
law. Consistent with that goal should be uniformity of
interpretation in construction of patent claims. It is not
rare that a patent is asserted against more than one
defendant in different forums, with conflicting holdings on
infringement. It would hardly promote uniformity of
patent law for us to bless a claim construction in one
district court, based on that court’s judging the credibility
and demeanor of the expert witnesses in one case, when a
different case might lead to a different result based on a
different district judge’s appraisal of different witnesses.
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                 3


We in fact might be confirming conflicting claim construc-
tions, the antithesis of uniformity. This problem might
increasingly exist in light of the AIA’s limits on the num-
ber of accused infringers that can be joined as defendants
in one lawsuit, thereby creating the possibility of more
lawsuits on the same patent, and more inconsistency,
than existed in the past. See 35 U.S.C. § 299(a); In re
EMC Corp., 677 F.3d 1351 (Fed. Cir. 2012).
    By our deferring to those determinations, conceding
our full review of the meaning of a claim term, which
should be based on the patent’s written description and
prosecution history, not the witnesses, hampers our
ability to interpret claims with full authority and hence to
ensure uniformity.
     Furthermore, claim construction is not a process that
normally involves historical facts. It primarily involves
reading the patent’s written description as well as the
prosecution history of the patent, and this court is quite
as able to do that as any district court, sometimes better.
It is true that there may be questions concerning what a
particular claim term meant to one skilled in the art at a
particular time, but, in my view, when the trial judge is
subjected to dueling experts selected for their views,
choosing which of them to credit hardly amounts to his-
torical fact-finding. To the extent that it does, the rele-
vant inquiry should be, not what the dueling experts say,
but what the inventor understood the term to mean when
he or she filed the patent application containing the claim
term in question. Courts should be reluctant to go beyond
the written record to help answer that question. It is too
subject to ex post facto thinking based on self-interest; the
inventor had his chance to define his invention and
should not be heard in later testimony to get another bite
at the apple by redefining that language.
4                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


    A realistic assessment of the problem in claim con-
struction in litigation recognizes that the patenting
process begins with an inventor and his or her attorney
drafting a written description and claims to describe and
specifically claim his or her invention. The claims will
usually then get negotiated in the Patent Office. The
issued claims are then used, pursuant to some perceived
business need or desire, by a different lawyer who had no
part in the drafting of the written description and claims,
who then tries in front of a lay judge to shoehorn an
accused infringer into claims that usually do not fit (or
else claim construction and infringement would not be at
issue).
    Hired “experts,” supporting the parties’ theories of in-
fringement or non-infringement take positions that are
also distinct and isolated from (and often different from)
those originally taken by the inventor and attorney, who
knew what the invention was and what positions were
taken in the Patent Office during prosecution. Thus, the
problem lies, not with lack of deference to district court
interpretation of claims by the Federal Circuit, but to the
multiplicity of actors contending in a competitive econo-
my. The actors striving to deal with a patent in district
court are often not those who made the invention, created
the patent, and hence knew exactly what it meant. The
solution does not lie in depriving the one institution
charged with ensuring uniformity of part of its authority.
    Much criticism has been directed at this court for al-
legedly ignoring all the fine work of district court judges
in construing patent claims. That criticism is premised
on the misperception that we do not give a district court’s
claim construction any deference. That is incorrect;
perhaps one even might say “clearly erroneous.”
    The rubric governing issues of law unfortunately does
read “no deference.” But even though we all know that
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                 5


the rubric governing procedural errors is the harsh “abuse
of discretion” language, all judges know that a finding of a
procedural error does not normally justify the term
“abuse.” Similarly, the “no deference” language is simply
established legal jargon for a holding that, having re-
viewed the record, we disagree. It has been stated in
some amicus briefs before the court that there are truly
factual issues involved in claim construction, particularly
what a claim term meant to one skilled in the art at a
particular time, and that such a determination should be
given deference. But we should not complicate the law
and change our precedent for such a situation. This court
should rarely overturn a district court’s claim construc-
tion on a finding of that nature.
    This appellate court, when asked to interpret the
claims of a patent carefully, notes and considers how the
district court construed the claims. If we disagree, it is
not without a degree of informal deference. Claims are to
be interpreted in light of the written description in the
patent specification, and in light of the prosecution. The
choice of expert witnesses by parties’ counsel, and their
demeanor, do not override those basic documents. Very
few scientists called as expert witnesses will lie, hence the
term “credibility,” useful in more conventional fact deter-
minations, such as whether a traffic light was red or not,
should not be controlling in construing claim limitations
in a patent.
     Claim construction is analogous to interpretation of
other legal instruments, such as contracts and legislation.
Each of these determinations is for the court, not a jury,
although each can be found to contain factual components
(it should be noted though that, at least in patent prose-
cution, the intent of neither the inventor-attorney nor the
patent examiner is usually at issue in claim construction).
Thus, beyond what the Court has held in Markman, there
6                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


is good analogical basis for considering claim construction
as similar to interpretation of these other legal instru-
ments. Moreover, to the extent that underlying consider-
ations create the “mongrel” nature of claim construction,
considering factual components to be subject to deference
under a clearly erroneous rule would implicate the Sev-
enth Amendment right to a jury trial on factual questions.
Such a procedure would further threaten the uniformity
that Congress intended in setting up this court as well as
the Supreme Court’s ruling that claim construction is not
for the jury.
    What the proponents of splitting construction into le-
gal and factual issues are in essence contending for is that
some issues in patent infringement are for the judge
(some claim construction issues), some are also for the
judge, but are of a factual nature, ordinarily as for a jury,
and some clearly for the jury, i.e., infringement. However,
in claim construction, simpler is better—claim construc-
tion in all its aspects for the judge, subject to review by
the appellate court, with sensible reliance on the prior
work of the trial judge. Creating a formal distinction
between fact-sounding issues subordinate to claim con-
struction and the ultimate claim construction is a compli-
cation that we should not foist on this court.
     A further point is that ultimately it should not matter
whether claim construction has a factual component to
which formal deference attaches or not. If, as I believe we
should, and do, give proper informal deference to the work
of judges of a subordinate tribunal, then we will or should
affirm when affirmance is appropriate. If, on the other
hand, we were to apply a more formal clearly erroneous
standard, judgments of subordinate courts are still not
unreviewable. If we were to find that the so-called factual
component, based on our review of the intrinsic record,
has been determined incorrectly, clearly we could find it
LIGHTING BALLAST   v. PHILIPS ELECTRONICS                7


to be incorrect even with a clearly erroneous standard.
Thus, this is an argument that should not much matter.
    Moreover, to the extent we were to overrule Cybor, or
modify it, and give formal deference to district courts, but
reserve the right to decide the ultimate issues of obvious-
ness and validity as questions of law, we would be engag-
ing in a kind of sham, giving with one hand and taking
back with the other. Doing so would bow to what
amounts to a cosmetic public, or judicial, exercise in order
to overcome the harsh rubric of “no deference.”
    To the extent that critics assert that de novo review
has not achieved the goal of uniformity, I believe that
deferring to district court judges on subsidiary, extrinsic
fact-related issues, and relying on experts hired for hav-
ing positions favorable to particular parties would likely
result in even less uniformity. At least under our current
regime, claim construction in all its aspects is reviewed by
one appellate court. And providing formal deference to
district courts in evaluating fact-related issues would
encourage migration away from reliance on the intrinsic
written record of the patent specification and its prosecu-
tion history.
    One should also make no mistake about it: if defer-
ence were to be given to rulings on complicated subject
matter, intensive appellate review would fade away (how
many appeals from the PTO are now reversed following
Zurko’s increase in the degree of deference given to the
relatively expert examining agency?), and so will uni-
formity. In addition, if determining whether an issue is
fact or law would determine the degree of deference
granted, parties would be arguing over that question, as
in appeals in veterans cases, rather than the real merits
of claim construction. As for the relatively high reversal
rate of claim construction at this court, I very much doubt
that it is primarily due to so-called issues of historical
8                   LIGHTING BALLAST   v. PHILIPS ELECTRONICS


fact; they are primarily due to our court’s review of the
claims in light of the specification, not to failure to judge
the credibility of contending expert witnesses. Besides,
the reversal rate on claim construction is apparently
coming down. See J. Jonas Anderson & Peter S. Menell,
Informal Deference: An Historical, Empirical, and Norma-
tive Analysis of Patent Claim Construction, 108 Nw. U. L.
Rev. _, 1 (forthcoming 2014).
    This case did not involve subsidiary findings resolving
disputes of historical fact. What was involved was wheth-
er there was corresponding structure to support “voltage
source means” for “providing a constant or variable mag-
nitude DC voltage between the DC input terminals”. The
panel found the means clause in the claim lacked suffi-
cient structure, and the specification similarly was lack-
ing, so it reversed the district court on the ground that the
claims were indefinite. Historical fact-finding was not
involved; reading the claims and written description was.
The en banc court should arrive at the same conclusion,
as the district court did not rely on any subsidiary find-
ings of fact. How a means plus function term is construed
under § 112, ¶ 6 is not fact, but claim construction, i.e.,
law.
    For the above reasons, in addition to the majority’s re-
liance on the doctrine of stare decisis, I support the court’s
decision not to overrule Cybor.
  United States Court of Appeals
      for the Federal Circuit
                 ______________________

        LIGHTING BALLAST CONTROL LLC,
                Plaintiff-Appellee,


                            v.


    PHILIPS ELECTRONICS NORTH AMERICA
               CORPORATION,
                 Defendant,


                           AND


  UNIVERSAL LIGHTING TECHNOLOGIES, INC.,
             Defendant-Appellant.
                 ______________________

                       2012-1014
                 ______________________

   Appeal from the United States District Court for the
Northern District of Texas in case no. 09-CV-0029, Judge
Reed O’Connor.
                ______________________

O’MALLEY, Circuit Judge, dissenting, with whom RADER,
Chief Judge, REYNA and WALLACH, Circuit Judges, join.
     District judges, both parties in this case, and the ma-
jority of intellectual property lawyers and academics
2                   LIGHTING BALLAST   v. PHILIPS ELECTRONICS


around the country will no doubt be surprised by today’s
majority opinion—and for good reason. The majority
opinion is surprising because it refuses to acknowledge
what experience has shown us and what even a cursory
reading of the Supreme Court’s decision in Markman v.
Westview Instruments, Inc., 517 U.S. 370 (1996), confirms:
construing the claims of a patent at times requires district
courts to resolve questions of fact. And, it puts itself at
odds with binding congressional and Supreme Court
authority when it refuses to abide by the requirements of
Rule 52(a)(6) of the Federal Rules of Civil Procedure,
which expressly instructs that, on appeal, all “findings of
fact . . . must not be set aside unless clearly erroneous.” It
is also surprising because, having, for the third time,
invited a broad swath of the intellectual property commu-
nity to express opinions regarding the merits of Cybor
Corp. v. FAS Technologies, Inc., 138 F.3d 1448 (Fed. Cir.
1998) (en banc), we now premise our refusal to change its
holding on principles of stare decisis—that, and a pro-
fessed inability to come up with a workable alternative to
de novo review. 1
     Criticism of and debate over Cybor have been wide-
spread since it issued—not only among legal scholars and
patent practitioners, but also among members of this
court. Despite this fact, the majority suggests, for the
first time in the ongoing debate over it, that Cybor is too
firmly established in our case law to be rethought. In
fact, it appears that some members of today’s 6–4 majori-
ty believe the pull of stare decisis is so strong that it
prevents them from acting on their long-term convictions


    1   We invited and received input regarding the
standard of review to be applied to claim construction in
Cybor itself, in Phillips v. AWH Corp., 415 F.3d 1303
(Fed. Cir. 2005) (en banc), and now in this case.
LIGHTING BALLAST v. PHILIPS ELECTRONICS                   3


that Cybor was wrongly decided. No reasoned application
of stare decisis principles supports that conclusion.
    To the extent the majority is motivated not just by a
resistance to change, but by concern over what standard
we should change to, those concerns can be allayed by
reference to Rule 52(a)(6) of the Federal Rules of Civil
Procedure, the Supreme Court’s case law governing that
rule, and a realistic assessment of what the claim con-
struction process entails.
    Because principles of stare decisis do not justify reten-
tion of the rule of Cybor and the appropriate standard of
review is dictated by Rule 52(a), I respectfully dissent.
                             I.
     In Cybor, this court held that claim construction, “in-
cluding any allegedly fact-based questions relating to
claim construction,” presents “a purely legal question”
subject to de novo review. Cybor, 138 F.3d at 1456. We
reached that conclusion even though, in Markman, the
Supreme Court repeatedly acknowledged the factual
component of claim construction. There, the Court:
(1) labeled claim construction as a “mongrel practice,”
(2) suggested that construing a patent’s claims “falls
somewhere between a pristine legal standard and a
simple historical fact,” (3) indicated that “there could be a
case in which a simple credibility judgment would suffice
to choose between experts whose testimony was equally
consistent with a patent’s internal logic,” (4) discussed the
need “to ascertain whether an expert’s proposed definition
fully comports with the specification and claims,” and
(5) described claim construction’s “evidentiary underpin-
nings.” Markman, 517 U.S. at 378, 388–90 (citation and
internal quotation marks omitted). Despite being urged
to do so by both parties, the Patent and Trademark Office,
and multiple amici, the majority refuses to overturn
4                   LIGHTING BALLAST   v. PHILIPS ELECTRONICS


Cybor. 2 The majority rests its judgment primarily on the
principles of stare decisis. It asserts that our fifteen years
of experience with Cybor teach that our continued de novo
review of all claim construction determinations is needed
to assure greater “reliability of outcome” and “interjuris-
dictional uniformity.” Maj. Op. at 14, 16.
   Considerations of stare decisis, however, do not justify
adhering to precedent that misapprehends the Supreme
Court’s guidance, contravenes the Federal Rules of Civil
Procedure, and adds considerable uncertainty and ex-
pense to patent litigation.
                             II.
     Stare decisis is an important part of our jurispru-
dence, and departing from our precedent is not something
we should do lightly. The doctrine “promotes the even-
handed, predictable, and consistent development of legal
principles, fosters reliance on judicial decisions, and
contributes to the actual and perceived integrity of the
judicial process.” Payne v. Tennessee, 501 U.S. 808, 827
(1991). It also serves to guard against “arbitrary discre-
tion.” Hubbard v. United States, 514 U.S. 695, 711 (1995)
(citations and internal quotation marks omitted).
     “Stare decisis is not an inexorable command[, howev-
er]; rather it ‘is a principle of policy and not a mechanical


    2    The majority describes three views espoused by
the parties and amici, giving substantially more attention
to the one that is consistent with the result the majority
reaches. Careful review of the materials submitted to the
court, and of the many academic and legal writings re-
garding Cybor since its issuance, show that a substantial
portion of the legal community to have considered the
issue believes Cybor was wrongly decided and flies in the
face of Rule 52 of the Federal Rules of Civil Procedure.
LIGHTING BALLAST v. PHILIPS ELECTRONICS                     5


formula of adherence to the latest decision.’” Payne, 501
U.S. at 828 (quoting Helvering v. Hallock, 309 U.S. 106,
119 (1940)). Its force varies from case to case, moreover—
carrying the most weight where reliance interests are at
stake, but the least weight where the departure from
precedent would not change substantive rights and would
“not affect the way in which parties order their affairs.”
Pearson v. Callahan, 555 U.S. 223, 233 (2009); see also
Payne, 501 U.S. at 828. “Revisiting precedent is particu-
larly appropriate where . . . a departure would not upset
expectations . . . and experience has pointed up the prece-
dent’s shortcomings.” Pearson, 555 U.S. at 233. The
Supreme Court has noted that departing from precedent
especially is appropriate “when governing decisions . . .
are badly reasoned.” Payne, 501 U.S. at 827 (“[W]hen
governing decisions are unworkable or are badly rea-
soned, ‘this Court has never felt constrained to follow
precedent.’” (quoting Smith v. Allwright, 321 U.S. 649,
665 (1944))); see also Helvering, 309 U.S. at 119 (caution-
ing against blindly applying stare decisis when adhering
to precedent would “involve[] collision with a prior doc-
trine more embracing in its scope, intrinsically sounder,
and verified by experience”).
    Consistent with this Supreme Court guidance, we
have explained that stare decisis does not stand in the
way of abrogating our case law—even entire bodies of it—
in at least three circumstances: when we conclude our
case law (1) was wrongly decided, see, e.g., Wilson v.
United States, 917 F.2d 529, 536 (Fed. Cir. 1990) (en
banc); (2) is at odds with congressional directives, see, e.g.,
Akamai Technologies, Inc. v. Limelight Networks, Inc.,
692 F.3d 1301, 1318 (Fed. Cir. 2012) (en banc); or (3) has
had negative consequences, see, e.g., Therasense, Inc. v.
Becton, Dickinson & Co., 649 F.3d 1276, 1288 (Fed. Cir.
2011) (en banc). With these principles in mind, this court
has not hesitated to revisit its own precedent. See, e.g.,
6                   LIGHTING BALLAST   v. PHILIPS ELECTRONICS


Cardiac Pacemakers, Inc. v. St. Jude Medical, Inc., 576
F.3d 1348 (Fed. Cir. 2009) (en banc); In re Seagate Tech.,
LLC, 497 F.3d 1360 (Fed. Cir. 2007) (en banc); Fisher v.
United States, 402 F.3d 1167 (Fed. Cir. 2005) (en banc);
Knorr–Bremse Systeme Fuer Nutzfahrzeuge GmbH v.
Dana Corp., 383 F.3d 1337 (Fed. Cir. 2004) (en banc).
Indeed, we have said that it is “‘[t]he province and obliga-
tion of the en banc court . . . to review the current validity
of challenged prior decisions.’” Robert Bosch, LLC v.
Pylon Mfg. Corp., 719 F.3d 1305, 1316 (Fed. Cir. 2013) (en
banc) (quoting United States v. Aguon, 851 F.2d 1158,
1167 n.5 (9th Cir. 1988) (en banc)). And, we have made
clear that this includes overturning precedent set by this
court en banc when appropriate. See Nobelpharma USA,
Inc. v. Implant Innovations, Inc., 141 F.3d 1059, 1068
(Fed. Cir. 1998) (overruling Atari, Inc. v. JS & A Grp.,
Inc., 747 F.2d 1422 (Fed. Cir. 1984) (en banc), by
“chang[ing] our precedent and hold[ing] that whether
conduct in procuring or enforcing a patent is sufficient to
strip a patentee of its immunity from the antitrust laws is
to be decided as a question of Federal Circuit law”).
    Thus, both Supreme Court case law and our own
teach that it is in cases like this one that stare decisis is
weakest.
                             III.
    Reversing Cybor will not “upset settled expectations
on anyone’s part.” Pearson, 555 U.S. at 233. The one
thing clear about Cybor is that no one in the legal com-
munity—except perhaps the members of the majority—
has come to believe that either the wisdom or vitality of
Cybor is settled. Whether one urges the retention of the
holding in Cybor (as do some amici) or urges its revision
(as do the parties, the Patent and Trademark Office, and
the rest of the amici), it is hard to dispute that tumult has
surrounded Cybor since it was decided. During its short
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  7


life, Cybor repeatedly has been criticized as poorly rea-
soned. That criticism has come from members of this
court, from district court judges, and from academics and
practitioners across the country.
     Our internal debate over Cybor has been heated, and
has not abated over time. There were several ardent
detractors from the rule announced in Cybor at the time it
was announced. See, e.g., Cybor, 138 F.3d at 1478, 1480
(Newman, J., additional views) (“By continuing the fiction
that there are no facts to be found in claim interpreta-
tions, we confound rather than ease the litigation pro-
cess. . . . However, the Supreme Court has relieved us of
adherence to this fiction, by its recognition of the factual
component of claim interpretation.”), id. at 1463 (Mayer,
C.J., concurring in the judgment) (stating that the Cybor
majority opinion “profoundly misapprehends” the Su-
preme Court’s decision in Markman); id. at 1473 (Rader,
J., dissenting from the pronouncements on claim interpre-
tation in the en banc opinion, concurring in the judgment,
and joining part IV of the en banc opinion). Even some of
the less vocal critics who concurred in the result in Cybor
expressed hesitation regarding the wisdom of either the
rule established or the legitimacy of its underpinnings.
See id. at 1463 (Plager, J., concurring) (“Whether this
approach to patent litigation will in the long run prove
beneficial remains to be seen.”); see also id. at 1463
(Bryson, J., concurring) (“[W]e approach the legal issue of
claim construction recognizing that with respect to certain
aspects of the task, the district court may be better situ-
ated than we are, and that as to those aspects we should
be cautious about substituting our judgment for that of
the district court.”).
    Since Cybor, our internal debate has continued. In
Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005) (en
banc), the order granting rehearing en banc asked the
8                   LIGHTING BALLAST   v. PHILIPS ELECTRONICS


parties to address whether it is “appropriate for this court
to afford any deference to any aspects of trial court claim
construction rulings.” Id. at 1328. Despite receiving
considerable input from the parties and amici, the Phil-
lips majority, without explanation, “decided not to ad-
dress that issue at this time.” Id. In dissent, however,
Judge Mayer levied a pointed criticism of Cybor, (1)
discussing “the absurdity[] of this court’s persistence in
adhering to the falsehood that claim construction is a
matter of law devoid of any factual component,” (2) stat-
ing that, “[i]n our quest to elevate our importance, we
have . . . disregarded our role as an appellate court . . .
undermin[ing] the legitimacy of the process, if not the
integrity of the institution,” and (3) observing that “we are
obligated by Rule 52(a) to review the factual findings of
the district court that underlie the determination of claim
construction for clear error.” Id. at 1330, 1332 (Mayer, J.,
dissenting).
     We have revisited the question multiple times since
then: (1) in 2006 in Amgen Inc. v. Hoechst Marion Rous-
sel, Inc., 469 F.3d 1039 (Fed. Cir. 2006); (2) in 2011 in
Retractable Technologies, Inc. v. Becton, Dickinson & Co.,
659 F.3d 1369 (Fed. Cir. 2011); and (3) even as recently as
a year ago in Highmark, Inc. v. Allcare Health Manage-
ment Systems, Inc., 701 F.3d 1351 (Fed. Cir. 2012), where
questions of claim construction were not even at issue.
See, e.g., Amgen, 469 F.3d at 1043 (Newman, J., dissent-
ing from denial of reh’g en banc) (“The Federal Circuit’s
position that patent interpretation requires more rigorous
appellate review than other fact/law issues has not with-
stood the test of experience. It is time to reopen the
question and to rethink, en banc, the optimum approach
to accuracy, consistency, and predictability in the resolu-
tion of patent disputes . . . .”); id. at 1046 n.3 (Moore, J.,
dissenting from denial of reh’g en banc) (highlighting the
problems Cybor has caused for district courts attempting
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  9


to construe patent claims); id. at 1045 (Gajarsa, Linn, &
Dyk, JJ., concurring in denial of reh’g en banc) (noting
that the concurrence “should not be read as . . . an un-
qualified endorsement of the en banc decision in Cybor”);
Retractable Techs., 659 F.3d at 1373 (Moore, J., dissenting
from denial of reh’g en banc) (“The Supreme Court held
that claim construction was a ‘mongrel practice.’ As such
it is clearly a mixed question of law and fact and defer-
ence should be given to the factual parts. . . . [W]e must
acknowledge the factual underpinnings of this analysis
and there should be deference.” (citation omitted)); High-
mark, 701 F.3d at 1362 (Moore, J., dissenting from denial
of reh’g en banc) (citing to Cybor and stressing that “[w]e
need to avoid the temptation to label everything legal and
usurp the province of the fact finder with our manufac-
tured de novo review”).
    Notably, not once during this internal dialogue over
the rule promulgated in Cybor did anyone contend that
stare decisis alone should put an end to our debate. Two
members of the current majority have been among the
harshest critics of Cybor—contending on multiple, and
even recent, occasions that it was poorly reasoned, im-
practical, and should be reversed. A third conceded that
Cybor’s rule may be too broad and perhaps should not
apply where, as here, the trial court was forced to resort
to extrinsic evidence to assess the meaning of claim
terms. In none of their discussions of Cybor was concern
regarding stare decisis raised. It certainly was never
exalted to the hard stop on further consideration of Cy-
bor’s merits that the majority now finds it to be.
    And, the debate over Cybor has not all been internal
to our court. The external debate has been both con-
sistent and widespread. See, e.g., Amicus Br. of United
States, Retractable Techs., Inc. v. Becton, Dickinson & Co.,
No. 11–1154, 2012 WL 5940288, at *20–21 (U.S. Nov. 28,
10                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


2012) (setting out the Solicitor General’s observation that
(1) “some claim-construction decisions will depend on a
district court’s resolution of factual questions,” (2) this
court’s “decision in Cybor does not identify any reason
that such factual findings should not be given the defer-
ence ordinarily required by Federal Rule of Civil proce-
dure 52(a),” and (3) “appellate courts routinely defer to
factual findings made by district courts and juries”).
District judges have opposed de novo review, describing it
as ill conceived and illogical. See, e.g., Amgen, Inc. v
Hoechst Marion Roussel, Inc., 339 F. Supp. 2d 202, 226
n.23 (D. Mass. 2004)) (describing the “conundrum” our
claim construction jurisprudence has created by “discour-
aging resort to extrinsic evidence while at the same time
urging courts to begin claim construction by considering
the plain and customary meaning of a term as understood
by one skilled in the art”); Judge James F. Holderman &
Halley Guren, The Patent Litigation Predicament in the
United States, Univ. Ill. J.L., Tech. & Pol’y 1, 6–7, 14–15
(2007) (noting that “claim construction involves many of
what one would consider to be factual determinations,”
stressing that the Supreme Court in Markman “said
nothing . . . about the de novo standard of review,” and
calling for a more deferential review of district court claim
constructions); The Honorable William G. Young & Pro-
fessor R. Carl Moy, Panel Discussion, High Technology
Law in the Twenty-First Century: Second Annual High
Technology Law Conference, 21 Suffolk Transnat’l L. Rev.
13, 19 (1997) (statements of the Honorable William G.
Young).
    As have practitioners.      See, e.g., Frederick L.
Whitmer, Claim Construction in Patent Cases: A Question
of Law?, 2 No. 6 Landslide 14, 16–17 (2010) (criticizing
our court’s interpretation of the Supreme Court’s guid-
ance in Markman and calling for recognition of “the
constituent factual component of claim construction
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  11


decision making”); Donald R. Dunner & Howard A. Kwon,
Cybor Corp v. FAS Technologies: The Final Say on Appel-
late Review of Claim Construction?, 80 J. Pat. & Trade-
mark Off. Soc’y 481, 492 (1998) (“[N]otwithstanding its
decision that claim construction was an issue for the
judge and not the jury, the Court in Markman II seemed
to consider the issue a mixed question of law and fact—a
characterization that would resist straightforward appli-
cation of the de novo standard.”); Luke L. Dauchot, The
Federal Circuit’s De Novo Review of Patent Claim Con-
struction: A Need for a More Balanced Approach, 18 Am.
Bar Ass’n Sec. Pub. I.P.L. 1, 4 (1999) (“A proper approach
recognizes that patent claim interpretation is ‘a mongrel
practice’ and delegates the fact-finding process to trial
courts . . . .”).
     Academics have been particularly harsh in their criti-
cism of Cybor and have suggested that we reverse it. See,
e.g., J. Jonas Anderson & Peter S. Menell, Informal
Deference: An Historical, Empirical, and Normative
Analysis of Patent Claim Construction, 108 Nw. U. L. Rev.
(forthcoming), Sept. 9, 2013 manuscript at *57–59 (argu-
ing that Cybor “misapprehends” Supreme Court prece-
dent, “deprive[s] the district court of critical evidence
bearing on claim meaning,” and “undermines the appel-
late process” by leaving “[t]he parties, the public, and the
appellate court” with an “anemic record—typically limited
to the intrinsic evidence”); Eileen M. Herlihy, Appellate
Review of Patent Claim Construction: Should the Federal
Circuit Be Its Own Lexicographer in Matters Related to
the Seventh Amendment?, 15 Mich. Telecomm. Tech. L.
Rev. 469, 515 (2009) (“A de novo standard of review . . .
runs contrary to the repeated and consistent word choices
made by the Court indicating that the Court considers
claim construction to be a mixed issue of fact and law.”);
Kimberly A. Moore, Markman Eight Years Later: Is Claim
Construction More Predictable?, 9 Lewis & Clark L. Rev.
12                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


231, 231 (2005) (observing the “concern among the bench
and bar that the Federal Circuit’s de novo review of
district court claim construction decisions . . . ha[s] caused
considerable unpredictability”); John R. Lane & Christine
A. Pepe, Living Before, Through, and With Markman:
Claim Construction as a Matter of Law, 1 Buff. Intell.
Prop. L.J. 59, 71 (2001) (“In Markman II, the Supreme
Court did concede that there are factual underpinnings to
claim construction determinations, raising the logical
question of whether de novo review is the appropriate
standard.” (footnote omitted)).
    In short, the only expectation about Cybor that ap-
pears “settled” is the expectation that one day this court
might recognize that Cybor is inconsistent with Supreme
Court precedent, the Federal Rules of Civil Procedure,
and the practical realities involved in the claim construc-
tion process, and would reverse it.
     Parties do not make claim drafting decisions based on
the standard of review we apply to trial court claim
constructions. Nor could they given the panel-dependent
nature of our own determinations. See Donald R. Dunner,
A Retrospective of the Federal Circuit’s First 25 Years, 17
Fed. Cir. B.J. 127, 130 (2007) (noting that many believe
“that Federal Circuit predictability is not what it should
be and that its decisions are often panel-dependent and
result-oriented”); R. Polk Wagner & Lee Petherbridge, Is
the Federal Circuit Succeeding? An Empirical Assessment
of Judicial Performance, 152 U. Pa. L. Rev. 1105, 1112
(2004) (“Our findings . . . indicate that claim construction
at the Federal Circuit is panel dependent.”). It is difficult
to accept the proposition that our claim construction
jurisprudence is a measure against which litigants make
important business or innovation decisions. Claim con-
struction disputes are very fact specific—patents do not
follow a formulaic structure, or even contain oft repeated
LIGHTING BALLAST v. PHILIPS ELECTRONICS                     13


language. Claims are drafted, redrafted, and amended in
ways intended to reflect and capture particular inventions
in a particular field, to avoid very specific prior art, and to
respond to the rejections of the unique patent examiner
involved in the application process. It is rare that any
two claims we review contain the same phrasing, and
even more rare that the context in which the phrasing is
used would not alter the meaning of even almost identical
words. 3 Compare Baldwin Graphic Sys., Inc. v. Siebert,
Inc., 512 F.3d 1338, 1342–43 (Fed. Cir. 2008) (finding
that, as a general rule, the words “an” or “a” in a patent
claim carry the meaning of “one or more”), with TiVo, Inc.
v. EchoStar Commc’ns Corp., 516 F.3d 1290, 1303 (Fed.
Cir. 2008) (finding that “whether ‘a’ or ‘an’ is treated as
singular or plural depends heavily on the context of its
use” and concluding that “claims and written description
in this case make clear that the singular meaning ap-
plies”). Combining the uniqueness of each claim term to
be reviewed with the variations in rationale employed by
the divergent members of this court, provides little practi-
cal guidance regarding how any claim construction dis-
pute might be resolved in this forum—and certainly not
the uniform reliability of outcome with which the majority
now credits our jurisprudence in this area.
    The fact that we have been engaging in a flawed prac-
tice for too long does not, alone, create the type of settled
expectations stare decisis is meant to protect. Because

    3   There are, of course, some common patent terms
that have been given universal meanings, or been charac-
terized as open-ended, rather than exclusive. These are
terms like “comprising,” “consisting of,” and “consisting
essentially of.” The meanings of most of these transition-
al terms were common to the patent drafting art well
before this Circuit was formed. And, litigants and district
courts are well aware of these conventions.
14                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


settled expectations will not be disrupted and no substan-
tive rights will be reordered, stare decisis simply does not
stand in the way of this court addressing the merits of
Cybor and acknowledging that the rule of law pronounced
therein is an incorrect one.
                            IV.
    It is also clear that stare decisis does not stand in the
way of overturning Cybor because Cybor is predicated on
a mischaracterization of the Supreme Court’s guidance in
Markman and ignores the claim construction process we
have ordered district courts to employ. In short, it need
not be followed because its premises are wrong. See
Wilson, 917 F.2d at 536 (overruling precedent that mis-
construed congressional intent).
    As noted above, Cybor misapprehends the Supreme
Court’s decision in Markman, ignoring numerous instanc-
es where the Court acknowledged that claim construction
can present factual questions. The Supreme Court did
not base its conclusion on the fact that a patent is a legal
instrument whose construction presents a pure question
of law. If it had, there would have been no need for the
Court to conduct such a thorough analysis of whether the
Seventh Amendment required a jury to resolve issues of
claim construction. That question would have needed no
discussion if claim construction were purely an issue of
law because juries have never been tasked with resolving
purely legal questions. See Markman, 517 U.S. at 376–
84; see also Cybor, 138 F.3d at 1464 (Mayer, C.J., concur-
ring in the judgment) (“Though it could have done so
easily, the Court chose not to accept our formulation of
claim construction: as a pure question of law to be decided
de novo in all cases on appeal. If it had, there would have
been no need for its extensive exegesis about the Seventh
Amendment and whether juries must construe claims
that have evidentiary underpinnings or whether the
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  15


importance of uniformity is best served by giving these
evidentiary questions of meaning to a judge.” (footnote
omitted)).
    While Cybor dismissed Markman’s discussion of the
factual aspects of claim construction as mere “prefatory
comments,” 138 F.3d at 1455, and insisted that, under
Markman, claim construction is a completely legal exer-
cise subject to de novo review, id. at 1456, that conclusion
does not flow from Markman. There, the Supreme Court
not only acknowledged claim construction’s factual as-
pects, it also said nothing to suggest that a de novo stand-
ard of review would be appropriate. See Retractable
Techs., 659 F.3d at 1373 (Moore, J., dissenting from
denial of reh’g en banc) (“The Supreme Court held that
claim construction was a ‘mongrel practice.’ As such it is
clearly a mixed question of law and fact and deference
should be given to the factual parts.” (citation omitted)).
Markman’s holding was limited to the Court’s determina-
tion “that the construction of a patent, including terms of
art within its claims, is exclusively within the province of
the court.” Markman, 517 U.S. at 372. There are many
circumstances in which trial judges act as triers of both
fact and law; in all of those, deference to the factual
components of that decision-making is undoubtedly due.
“Stating that something is better decided by the judge is
not the same as saying it is a matter of law.” Highmark,
701 F.3d at 1362 (Moore, J., dissenting from denial of
reh’g en banc). 4 And even saying something is a matter of

   4     This mistake is one repeated in some of the ami-
cus briefs that support retention of Cybor, stating that
Cybor must be retained so as to avoid having to submit
claim construction issues to the jury. See Amicus Br. of
Microsoft Corp. at 4–5; Amicus Br. of Intellectual Prop.
Inst. of William Mitchell Coll. of Law at 10–12. But, the
Supreme Court made clear in Markman that it had
16                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


law does not answer the question of the standard of
review an appellate court should apply. See Pierce v.
Underwood, 487 U.S. 552, 560, 562 (1988) (observing that,
“[i]n some cases, such as the present one, the attorney’s
fee determination will involve a judgment ultimately
based on a purely legal issue governing the litigation,” but
concluding that “sound judicial administration counsels[]
deferential review of a district court’s decision regarding
attorney’s fees” despite its legal character).
    Those amici who find great significance in the Su-
preme Court’s citation to Miller v. Fenton, 474 U.S. 104
(1985), in Markman miss the mark. That citation does
not, as those amici claim, decide the fact/law question or
the question of the appropriate level of appellate review of
claim construction determinations. In Miller, the Su-
preme Court concluded that the ultimate question of
whether a confession was sufficiently voluntary to com-
port with due process, while a mixed question of fact and
law, was subject to independent federal review. As the
Court noted in Markman, it had concluded in Miller that,

institutional efficiency reasons for taking claim construc-
tion away from the jury, unhampered as it was by Sev-
enth Amendment concerns; the decision to give claim
construction to trial judges did not turn on a fact/law
distinction. See Markman, 517 U.S. at 384 n.10 (“Because
we conclude that our precedent supports classifying the
question as one for the court, we need not decide either
the extent to which the Seventh Amendment can be said
to have crystallized a law/fact distinction . . . or whether
post-1791 precedent classifying an issue as one of fact
would trigger the protections of the Seventh Amendment
if (unlike this case) there were no more specific reason for
decision.” (citations omitted)). Because the views of these
amici are based on this legally flawed premise, undue
reliance on them is misplaced.
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  17


where a question “falls somewhere between a pristine
legal standard and a simple historical fact,” the conclu-
sion as to which judicial actor is best positioned to decide
a question at times turns on the sound administration of
justice, rather than a pure fact/law distinction. 517 U.S.
at 388. Though, in Miller, the Court decided that the
sound administration of justice supported the conclusion
that the ultimate constitutional question of whether a
confession was voluntary should be reserved for federal,
rather than state, courts, Miller says nothing about the
standard of review one federal tribunal should apply to
the inquiries of another, or how the sound administration
of justice would divvy up the responsibility of claim con-
struction as between the trial and appellate courts.
    In fact, in Miller itself, the Court concluded that a
presumption of correctness still must be afforded to all
“subsidiary factual questions” decided by the state courts.
474 U.S. at 112. And, the Court was careful to explain
that its determination of what the sound administration
of justice called for vis-à-vis the federal and state courts
was reached in the absence of congressional directives to
the contrary.
     In Markman, the Supreme Court said that judicial ef-
ficiencies supported allocation of claim construction
determinations to the court rather than the jury. It did
not say that “subsidiary factual determinations” made by
trial courts ceased to be subject to the deference congres-
sionally mandated by the Federal Rules of Civil Proce-
dure, however. And, it did not say that it was this court
and only this court to which the question should be allo-
cated. Indeed, in Cooter & Gell v. Hartmarx Corp., 496
U.S. 384 (1990), decided five years after Markman, the
Court addressed the question of how the sound admin-
istration of justice can impact the standard of review of
questions that involve both factual and legal components.
18                  LIGHTING BALLAST    v. PHILIPS ELECTRONICS


There, while the Court acknowledged that some purely
legal inquiries are involved in determinations pursuant to
Rule 11 of the Federal Rules of Civil Procedure, it found
that the entire determination must be reviewed by the
courts of appeals under an abuse of discretion standard.
Id. at 403–04. Returning to the same type of inquiry
employed in Miller, the Supreme Court explained that
where, as in a Rule 11 inquiry, the line between fact and
law is difficult to divine and the trier of fact needs flexibil-
ity to decide unique facts that resist generalization, it is
the trial judge who is the judicial actor best suited to
decide the question. Id. In such instances, the Court
found that the sound administration of justice to which it
harkened in Miller and again in Markman mandated a
fully deferential standard of review.
    It is notable that at least one Supreme Court Justice
on the Court when Markman was decided believes that, if
Markman can be said to have decided the standard of
review to be applied to claim construction determinations,
it decided that question very differently than we did in
Cybor and than we continue to do today. In Gasperini v.
Center for Humanities, Inc., 518 U.S. 415 (1996), dissent-
ing from the judgment there, Justice Stevens described
the Court’s decision in Markman as one of three that term
in which courts of appeals were “assigned . . . the task of
independently reviewing similarly mixed questions of law
and fact,” and described the nature of that review as one
in which appellate courts are required “to construe all
record inferences in favor of the factfinder’s decision and
then to determine whether, on the facts found below, the
legal standard has been met.” Id. at 442–43 (Stevens, J.,
dissenting).
    Markman’s citation to Miller, accordingly, lends no
support to the notion that Markman somehow dictated
the result in Cybor. It only helped explain why the court,
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  19


rather than the jury, was chosen as the appropriate
decision maker. Cybor was not compelled by the Supreme
Court’s guidance; as explained in section V below, it is
actually a wide departure from it.
    Cybor also ignores the realities of the claim construc-
tion process. As our en banc court in Phillips observed:
   [B]ecause extrinsic evidence can help educate the
   court regarding the field of the invention and can
   help the court determine what a person of ordi-
   nary skill in the art would understand claim
   terms to mean, it is permissible for the district
   court in its sound discretion to admit and use such
   evidence. In exercising that discretion, and in
   weighing all the evidence bearing on claim con-
   struction, the court should keep in mind the flaws
   inherent in each type of evidence and assess that
   evidence accordingly.
415 F.3d at 1319 (emphases added). Cybor cannot be
squared with this court’s own well-respected description
of the very claim construction process to which it purports
to apply.
    The majority concedes that claims are to be interpret-
ed from the perspective of one of skill in the art at the
time of the invention unless it appears from the surround-
ing record—the specification and prosecution history—
that the patentee acted as his own lexicographer to pro-
vide a contrary meaning. Maj. Op. at 32 (citing Phillips,
415 F.3d at 1314). It concludes, however, that all we need
to put ourselves into the shoes of a skilled artisan are the
patent documents and, perhaps (though not necessarily),
some explanation regarding the technology at issue and a
dictionary or treatise. It believes we do not need to hear
from experts regarding the state of the known science or
art at the time of the invention, the commonly understood
20                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


meaning, if any, of the particular terms or phrases em-
ployed, the level of education and skill one reading such a
patent would have, or whether there are particular trea-
tises or dictionaries to which a skilled artisan would have
turned at the time. See id. at 22. And, it believes that the
conclusions it gleans from the patent documents, includ-
ing the entirety of the prosecution history, expert descrip-
tions of the technology, and dictionaries are all legal
conclusions; that no finding made by any judicial officer in
the process of claim construction constitutes a subsidiary
factual one. See id. at 22–23.
    The majority justifies these conclusions by analogiz-
ing the claim construction process to the interpretation of
statutes, where courts routinely consider contemporane-
ous dictionaries or even the testimony of historians to
help determine the meaning of words and phrases there-
in. See id. The analogy is not a sound one, however.
    Statutes are duly enacted laws of broad applicability.
Their interpretation by an appellate court is binding on
all who would be impacted by that statute in that circuit,
whether parties to the original action or not. They are
drafted by those with congressional authority to enact
such laws and are to be given a meaning common to all.
Patents are drafted ex parte, are revised in a closed-door
examination process, their terms are, as noted before,
unique to the invention at issue, and are assertable only
against individual infringers in private actions. The two
are simply not of the same ilk. See Markman v. Westview
Instruments, Inc., 52 F.3d 967, 998 n.8 (Fed. Cir. 1995)
(Mayer, J., concurring in the judgment) (“Patents cannot
be baby statutes . . . .”); Amgen, 469 F.3d at 1040–41
(Michel, C.J., dissenting from denial of reh’g en banc)
(observing that, in statutory interpretation, a judge
construes terms from the perspective of a skilled legal
artisan looking at the words only, not from the perspec-
LIGHTING BALLAST v. PHILIPS ELECTRONICS                 21


tive of a different individual—one skilled in the relevant
field of technology in light of the intrinsic and extrinsic
record).
     The parties agree that there were disputed factual
questions in this case that required examination of ex-
trinsic evidence. In the proceedings before the district
court and again on appeal, the parties disputed whether
the claim term “voltage source means” should be treated
as a means-plus-function limitation under 35 U.S.C.
§ 112, ¶ 6. Lighting Ballast Control LLC v. Philips Elecs.
N. Am. Corp., 498 F. App’x 986, 989–90 (Fed. Cir. 2013).
The use of the word “means” triggers the presumption
that the limitation is a means-plus-function term, but
that presumption “may be rebutted if the claim itself
recites sufficient structure for performing the function.”
Id. at 990. The parties focused on whether “voltage
source means” denoted a particular structure to those of
skill in the art (i.e., whether the term had a specific
meaning used by those of skill in the art to describe a
defined structure or specific class of structures). See id.
If skilled artisans understood “voltage source means” to
refer to a defined structure, it would not be considered a
means-plus-function limitation. Id. The specification and
prosecution history, however, did not resolve the question.
Thus, it became necessary and appropriate to look outside
the intrinsic record and to consider the testimony of
Lighting Ballast’s expert, Dr. Roberts. See id.; see also
Rembrandt Data Techs., LP v. AOL, LLC, 641 F.3d 1331,
1341 (Fed. Cir. 2011) (“When determining whether a
claim term recites sufficient structure, we examine
whether it has an understood meaning in the art.”).
When situations like this arise, it is appropriate—and
sometimes necessary—to make findings based on extrin-
sic evidence that relate to the meaning of a disputed term.
Resolution of these fact-intensive disputes is an area
22                   LIGHTING BALLAST   v. PHILIPS ELECTRONICS


where district courts’ expertise deserves the deference
that Rule 52(a)(6) requires.
    Both parties, the PTO, and most amici agree that
there are factual components to claim construction. Even
among the amici that favor retaining Cybor’s de novo
review of all aspects of claim construction, most readily
identified factual questions that arise during claim con-
struction. Microsoft Corp., for instance, advocated retain-
ing Cybor, but nonetheless listed numerous factual
questions that it concedes could arise during claim con-
struction and would require the court to:
     determin[e] the field[s] of the invention and the
     knowledge of a person having ordinary skill in the
     art; determin[e] the art-accepted meanings of
     terms used in an issued claim and also used in the
     specification and/or prior art; determin[e] the date
     of the invention and/or the effective filing date of
     the patent application; determin[e] whether a
     proposed construction would exclude all embodi-
     ments in the specification or, conversely, whether
     any embodiment supports the construed issued
     claim; identifying explicit or implicit definitions in
     the specification; [and] determin[e] the disclosure
     of cited prior art references (which are part of the
     ‘intrinsic evidence’ for claim construction) assert-
     ed as invalidating prior art and/or distinguished
     in the prosecution history.
Amicus Br. at 4–5. Similarly, the Austin Intellectual
Property Law Association observed that “district courts
are charged with taking evidence of specialized meanings
in . . . patent interpretation.” Amicus Br. at 8. Likewise,
the brief filed by Cisco Systems, Inc. et al. acknowledged
that a case could arise where “a question of meaning
peculiar to a trade or profession [could] turn[] on the
resolution of contested questions of historical fact.”
LIGHTING BALLAST v. PHILIPS ELECTRONICS                   23


Amicus Br. at 24–26 (citation and internal quotation
marks omitted).
    In sum, it is hard to understand how either the major-
ity in Cybor or the majority here can dispute that claim
construction sometimes requires a district court to resolve
contested factual issues. Cybor is, thus, based on a faulty
premise—that claim construction is a purely legal exer-
cise. This reveals deep flaws in Cybor’s reasoning, justify-
ing a departure from it. See Payne, 501 U.S. at 827
(permitting departure from decisions that prove “unwork-
able or are badly reasoned”).
                             V.
    Stare decisis also must give way because, by refusing
to acknowledge the factual component of claim construc-
tion, Cybor contravenes the clear directives of Federal
Rule of Civil Procedure 52(a)(6). When a district court
makes findings of fact—as claim construction sometimes
requires—Rule 52(a)(6) provides clear instructions to this
court: “Findings of fact, whether based on oral or other
evidence, must not be set aside unless clearly errone-
ous . . . .” The rule is clear on its face, and decisions
interpreting it show that it makes no exception with
regard to fact-finding in the claim construction context.
As the Supreme Court has observed, “Rule 52(a) broadly
requires that findings of fact not be set aside unless
clearly erroneous. It does not make exceptions or purport
to exclude certain categories of factual findings from the
obligation of a court of appeals to accept a district court’s
findings unless clearly erroneous.” Pullman–Standard v.
Swint, 456 U.S. 273, 287 (1982); see also Bose Corp. v.
Consumers Union of U.S., Inc., 466 U.S. 485, 498 (1984)
(“We have repeatedly held that . . . Rule [52(a)] means
what it says.”). Thus, there is direct conflict between
Cybor—which expressly calls for de novo review of “any
allegedly fact-based questions relating to claim construc-
24                   LIGHTING BALLAST    v. PHILIPS ELECTRONICS


tion,” 138 F.3d at 1456—and Rule 52(a)(6)—which re-
quires deference to all fact-findings that are not clearly
erroneous. See Amicus Br. of United States at 9–13
(noting that “[a]ppellate courts must defer to a trial
court’s factual findings under Rule 52(a)” and that,
“[g]iven the clear command of Rule 52(a), no justification
exists to treat claim construction any differently”).
    The law governing obviousness confirms Rule 52(a)’s
broad applicability in patent disputes.        Obviousness
presents a question of law subject to de novo review, but it
involves a number of subsidiary fact-findings. As the
Supreme Court observed:
     While the ultimate question of patent validity is
     one of law, . . . the § 103 condition . . . lends itself
     to several basic factual inquiries. Under § 103,
     the scope and content of the prior art are to be de-
     termined; differences between the prior art and
     the claims at issue are to be ascertained; and the
     level of ordinary skill in the pertinent are re-
     solved.
Graham v. John Deere Co. of Kansas City, 383 U.S. 1, 17
(1966). According to the Court, “[t]his description of the
obviousness inquiry makes it clear that whether or not
the ultimate question of obviousness is a question of fact
subject to Rule 52(a), the subsidiary determinations of the
District Court, at the least, ought to be subject to the
Rule.” Dennison Mfg. Co. v. Panduit Corp., 475 U.S. 809,
811 (1986); see also Panduit Corp. v. Dennison Mfg. Co.,
810 F.2d 1561, 1569 (Fed. Cir. 1987) (“Rule 52(a) is appli-
cable to all findings on the four inquiries listed in Gra-
ham: scope and content of prior art; differences between
prior art and claimed invention; level of skill; and objec-
tive evidence . . . .”). Importantly, one of the key fact
questions in an obviousness inquiry is what a prior art
reference teaches—often, what is claimed and described
LIGHTING BALLAST v. PHILIPS ELECTRONICS                   25


in a previously issued patent. See Graham, 383 U.S. at
17. And, all findings regarding the scope and content of
the prior art are subject to clear error review. See Pan-
duit, 810 F.2d at 1569. That we trust jurors to define the
scope of patent claims in this context, but are less than
comfortable allowing trial judges to do the same when
considering the asserted patent claims is at least anoma-
lous. Cybor is thus out of step with our other jurispru-
dence that faithfully applies Rule 52(a) in patent cases.
    This conflict between Cybor and the Federal Rules of
Civil Procedure means our case law must fall. As this
court has observed,
    The Federal Rules of Civil Procedure were prom-
    ulgated by the Supreme Court pursuant to statu-
    tory authority and were implicitly adopted by
    Congress after transmission to Congress in their
    proposed form. See 28 U.S.C. §§ 2071–2074. In
    light of this statutory promulgation scheme, the
    Supreme Court has held that the Federal Rules of
    Civil Procedure are deemed to have “the force
    [and effect] of a federal statute.”
Bright v. United States, 603 F.3d 1273, 1279 (Fed. Cir.
2010) (alteration in original) (quoting Sibbach v. Wilson &
Co., 312 U.S. 1, 13 (1941)). Our cases dealing with the
application of stare decisis where statutory interpretation
is at issue thus provide useful guidance.
    We often have held that stare decisis does not prevent
our court from overturning its precedent when we con-
clude our prior jurisprudence runs contrary to what we
believe are a statute’s directives. See, e.g., Akamai Techs.,
Inc. v. Limelight Networks, Inc., 692 F.3d 1301, 1306 (Fed.
Cir. 2012) (en banc) (overruling multiple decisions of this
court where “we held that in order for a party to be liable
for induced infringement, some other single entity must
26                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


be liable for direct infringement”); Wilson v. United
States, 917 F.2d 529, 536 (Fed. Cir. 1990) (en banc) (over-
turning our earlier decision in Ulmet v. United States, 822
F.2d 1079 (Fed. Cir. 1987), saying: “We have revisited the
legislative history of [10 U.S.C.] § 1163(d) in this case.
Our examination has brought to light that the legislative
history of the sanctuary provision demands a different
result from that reached in Ulmet.”); Cardiac Pacemakers,
Inc. v. St. Jude Med., Inc., 576 F.3d 1348 (Fed. Cir. 2009)
(en banc) (overruling prior case law because we believed
that case law did not properly interpret 35 U.S.C.
§ 271(f)). In all of these instances, we concluded that
stare decisis did not provide a basis for adhering to prece-
dent that ran counter to the dictates of a statute, as
properly interpreted.
    We should bring our case law in line with the direc-
tives of Rule 52(a)(6), as we are required to do, and as we
have done with respect to numerous statutory commands
in the past. See Amicus Br. of United States at 9–13
(urging the court to overturn Cybor because it runs coun-
ter to Rule 52(a)’s clear commands); Amicus Br. of Am.
Bar Ass’n at 12–13 (same); Amicus Br. of Prof. Peter
Menell at 17–20 (In light of Rule 52(a)’s commands, “the
Federal Circuit must defer to trial judges’ factual deter-
minations in claim construction rulings.”); Amicus Br. of
Am. Intellectual Prop. Law Ass’n at 4–6, 6 n.6 (“There is
no reason for the review of patent claim construction,
where the trial court makes constituent determinations of
fact, to be any different from review of other ultimate
issues of law that have factual underpinnings.”); Amicus
Br. of Fed. Cir. Bar Ass’n at 7; Amicus Br. of Intellectual
Prop. Owners Ass’n at 7 (stressing that Rule 52(a) re-
quires deference to district courts’ findings of claim con-
struction facts); Amicus Br. of Conn. Intellectual Prop.
Law Ass’n at 12 (faulting Cybor for “say[ing] that patent
cases have their very own Fed. R. Civ. P. 52(a)(6),” even
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  27


though there is “no legitimate reason to treat patent cases
differently from other cases”); Amicus Br. of Fed’n Inter-
nationale Des Conseils en Propriete Intellectuelle at 12
(noting that de novo review of findings of claim construc-
tion facts “violates Federal Rule of Civil Procedure
52(a)(6)”).
    The majority discounts concerns about the dictates of
Rule 52(a)(6) by citing the Supreme Court’s statement in
Pullman–Standard v. Swint that Rule 52(a) does not
provide a clear formula for distinguishing fact from law.
Maj. Op. at 34 (citing Pullman–Standard, 456 U.S. at
288). As the Court made clear in Pullman–Standard
itself when reversing the Fifth Circuit’s refusal to give
deference to a trial court’s factual inquiry, the fact that
our inquiry might be a difficult one does not excuse the
failure to undertake it. See Pullman–Standard, 456 U.S.
at 288–90. Indeed, the Supreme Court has on numerous
occasions charged the courts of appeals with drawing
distinctions between subsidiary or “historical facts” and
the ultimate legal conclusion regarding the import of
those facts, and with adjusting their standard of review
accordingly. See Cooper Indus., Inc. v. Leatherman Tool
Grp., Inc., 532 U.S. 424, 440 n.14 (2001) (“While we have
determined that the Court of Appeals must review the
District Court’s application of the Gore test [set out in
BMW of North America, Inc. v. Gore, 517 U.S. 559 (1996),]
de novo, it of course remains true that the Court of Ap-
peals should defer to the District Court’s findings of fact
unless they are clearly erroneous.”); Ornelas v. United
States, 517 U.S. 690, 699 (1996) (holding that “determina-
tions of reasonable suspicion and probable cause should
be reviewed de novo on appeal” but “hasten[ing] to point
out that a reviewing court should take care both to review
findings of historical fact only for clear error and to give
due weight to inferences drawn from those facts by resi-
dent judges and local law enforcement officers”); Thomp-
28                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


son v. Keohane, 516 U.S. 99, 110–12 (1995) (concluding
that there are two distinct inquiries—one purely factual
and another a mixed question—involved in “[t]he ultimate
‘in custody’ determination for Miranda purposes,” with
deference to findings on all factual components due). As
the PTO explains, “Congress gave no indication in the
patent laws that it intended to displace the fundamental
principle of appellate review for clear error.” Amicus Br.
of United States at 12. 5
                            VI.
    The “undesired consequences” flowing from this
court’s claim construction jurisprudence also justify
departing from the law set out in Cybor. Cybor, 138 F.3d
at 1481 (Newman, J., additional views); see also Pearson,
555 U.S. at 233 (stating that revisiting case law is “par-


     5  The scope of this court’s obligation to abide by the
dictates of Rule 52(a)(6) is currently before the Supreme
Court. In Highmark Inc. v. Allcare Health Management
Systems, Inc., 687 F.3d 1300 (Fed. Cir. 2012), cert. grant-
ed, 134 S. Ct. 48 (Oct. 1, 2013) (No. 12–1163), the question
presented is “[w]hether a district court’s exceptional-case
finding under 35 U.S.C. § 285, based on its judgment that
a suit is objectively baseless, is entitled to deference.”
Petition for Writ of Certiorari, Highmark Inc. v. Allcare
Health Mgmt. Sys., Inc., 2013 WL 1209137, at *i (U.S.
Mar. 25, 2013) (No. 12–1163). The petitioner asserts that
deference must be given to all aspects of a district court’s
§ 285 determinations because, among other reasons, there
are subsidiary findings of fact which Rule 52(a)(6) de-
mands be reviewed for clear error. See id. at *19–20. If
the Supreme Court premises its holding in Highmark
entirely or even partially on the dictates of Rule 52(a)(6),
such a ruling would make clinging to Cybor for no reason
other than a resistance to change completely untenable.
LIGHTING BALLAST v. PHILIPS ELECTRONICS                    29


ticularly appropriate” where experience has revealed its
shortcomings). By refusing to acknowledge the factual
component of claim construction, Cybor has made the
claim construction process less transparent, accurate,
predictable, and efficient, thereby imposing high “social
costs.”   See Anderson & Menell, supra, at *60–61;
Whitmer, supra, at 16 (lamenting the “high reversal rate”
with respect to claim construction that is the “conse-
quence of the Cybor uncertainty principle”); Lane & Pepe,
supra, at 71–73 (examining the uncertainty that results
from de novo review).
                             A.
     The primary interests furthered by stare decisis—a
doctrine rooted in policy—support departing from Cybor,
not adhering to it. See Helvering, 309 U.S. at 119 (observ-
ing that stare decisis “is a principle of policy”). Preserving
the stability of the law and protecting the public’s ability
to “rel[y] on judicial decisions” are the central interests
furthered by stare decisis. Payne, 501 U.S. at 827. By
withholding deference to district courts’ findings of claim
construction facts, however, the interests of stability and
predictability are disserved. See Highmark, 701 F.3d at
1362 (Moore, J., dissenting from denial of reh’g en banc)
(“When we convert factual issues, or mixed questions of
law and fact, into legal ones for our de novo review, we
undermine the uniformity and predictability goals this
court was designed to advance.”); see also Amicus Br. of
Prof. Peter Menell at 15 (observing that “[t]he[] effects [of
de novo review of claim construction determinations]
continue to cast doubt on the predictability of patent
litigation, discourage settlements following claim con-
struction trial, delay resolution of patent disputes, and
run up the overall costs of patent litigation”). Indeed, our
resistance to changing Cybor is directly contrary to the
purposes of Rule 52(a)(6): to promote stability in the
30                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


judicial system by (1) avoiding undermining the legitima-
cy of district courts and (2) preventing unnecessary ap-
peals by discouraging appellate retrial of factual issues.
See Fed. R. Civ. P. 52 advisory committee’s note (1985).
     Under the Cybor regime, a district court can construe
a claim term, and an entire trial can follow premised on
that construction. When the district court’s judgment is
appealed, however, we review every aspect of its claim
construction de novo, leaving us largely free to reinterpret
claims—both upsetting parties’ expectations and undoing
a tremendous amount of parties’ and district courts’ work
in the process. See Cybor, 138 F.3d at 1476 (Rader, J.,
dissenting from the pronouncements on claim interpreta-
tion in the en banc opinion) (“To get a certain claim inter-
pretation, parties must go past the district court’s
Markman I proceeding, past the entirety of discovery,
past the entire trial on the merits, past post-trial motions,
past briefing and argument to the Federal Circuit—
indeed past every step in the entire course of federal
litigation, except Supreme Court review.”). Once here,
moreover, as noted earlier, “[c]ommentators have ob-
served that claim construction appeals are ‘panel depend-
ent’ which leads to frustrating and unpredictable results
for both the litigants and the trial court.” Retractable
Techs., 659 F.3d at 1370 (Moore, J., dissenting from
denial of reh’g en banc) (citations omitted). And, while
the majority says that it is “no longer true” that there is a
high reversal rate with respect to claim constructions by
district courts, Majority Opinion at 34, that is not what
trial judges, litigants, and academics contend. As Profes-
sor Peter Menell says in his amicus brief before this court:
“Although we document a significant drop in the claim
construction reversal rate since the Phillips decision,
there still remains a high reversal rate compared to other
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  31


areas of federal practice.” 6 Amicus Br. at 15; see also
Amicus Br. of Ass’n of Bar of N.Y. (“The high reversal rate
of the district court claim construction, documented in
numerous studies, is universally acknowledged. It is not
an overstatement to conclude that the reversal rate has
had a detrimental effect on the parties, the court, and the
credibility of the patent system generally.” (footnote
omitted)). Departing from Cybor and reviewing claim
construction findings for clear error would introduce
greater stability and less expense, and would afford the
appropriate respect for district courts’ factual determina-
tions—respect that Rule 52(a)(6) demands. As a conse-
quence, this case presents an instance where overturning
this court’s precedent will lead to greater stability and
predictability, not less.
                            B.
    Refusing to acknowledge that claim construction has
a factual component effectively “deprives th[is] court, and
the parties, of the accumulated progress and experience of
the trial, including the findings of the trial judge, and
leaves us on appeal with an expurgated record and gener-
ally inferior basis of decision.” Cybor, 138 F.3d at 1481
(Newman, J., additional views). By affording zero defer-
ence to any aspect of a district court’s claim construction,


   6    The majority is incorrect that “every amicus brief
that complains about high reversal rates relies on data
that are seven to ten or more years old.” Maj. Op. at 34.
Professor Menell’s amicus brief to this court describes his
recent research with Professor Jonas Anderson, which
reveals that de novo review of claim construction contin-
ues to contribute to “alarming levels of appellate rever-
sals.” Amicus Br. at 13–14; see also Anderson & Menell,
supra, at *6 (examining this court’s claim construction
jurisprudence from 2000 through 2011).
32                  LIGHTING BALLAST   v. PHILIPS ELECTRONICS


we ignore the reality that we lack the tools that district
courts have available to resolve factual disputes fairly and
accurately. As Judge Rader observed in dissenting in
part in Cybor,
     the trial judge enjoys a potentially superior posi-
     tion to engage in claim interpretation. For the
     complex case where the claim language and speci-
     fication do not summarily dispose of claim con-
     struction issues, the trial court has tools to
     acquire and evaluate evidence that this court
     lacks. Trial judges can spend hundreds of hours
     reading and rereading all kinds of source materi-
     al, receiving tutorials on technology from leading
     scientists, formally questioning technical experts
     and testing their understanding against that of
     various experts, examining on site the operation
     of the principles of the claimed invention, and de-
     liberating over the meaning of the claim language.
     If district judges are not satisfied with the proofs
     proffered by the parties, they are not bound to a
     prepared record but may compel additional
     presentations or even employ their own court-
     appointed expert.
138 F.3d at 1478.
    The Supreme Court has explained that “[t]he trial
judge’s major role is the determination of fact, and with
experience in fulfilling that role comes expertise.” Ander-
son v. Bessemer City, 470 U.S. 564, 574 (1985). The Court
also reminds us that “deferential review of mixed ques-
tions of law and fact is warranted when it appears that
the district court is better positioned than the appellate
court to decide the issue in question or that probing
appellate scrutiny will not contribute to the clarity of
legal doctrine.” Salve Regina Coll. v. Russell, 499 U.S.
225, 233 (1991); see also Cooter, 496 U.S. at 403 (calling
LIGHTING BALLAST v. PHILIPS ELECTRONICS                   33


for deference to the decisions of “‘the judicial actor . . .
better positioned than another to decide the issue in
question’” (alteration in original) (quoting Miller, 474 U.S.
at 114)). District courts should be encouraged to resolve
the factual questions bearing on claim construction and to
develop a thorough record setting out their findings and
the evidence supporting their conclusions. When they do,
we overstep the bounds of our duty under Rule 52(a)(6) by
duplicating, or ignoring, rather than deferring to that
process. Anderson, 470 U.S. at 573; cf. Highmark, 701
F.3d at 1365 (Reyna, J., dissenting) (urging that we
“respect[] the enduring balance between the trial judge
and the appellate panel in carrying out their distinct
responsibilities” by applying clear error review to trial
court findings).
    The concurrence downplays the extent to which we
usurp the trial court’s function by adherence to Cybor by
arguing both that claim construction rarely involves
credibility determinations and that we are “quite as able”
as district courts—or “sometimes better” able—to review
the relevant documents in the record, such as the patent’s
prosecution history. Concurrence at 3. And the majority
echoes these themes, contending that claim construction
does not present questions of fact because it does not turn
on credibility determinations and that leaving these
questions to de novo review by our court assures greater
correctness of result. The Supreme Court has made clear,
however, that this narrow view of the trial court’s fact-
finding function is an inaccurate one. The district court’s
expertise is “not limited to the superiority of the trial
judge’s position to make determinations of credibility,”
but instead extends to all factual determinations. Ander-
son, 470 U.S. at 574. These determinations include
findings “based on physical or documentary evidence or
inference from other facts.” Id. The Supreme Court has
explained that Rule 52(a) requires deference to these
34                   LIGHTING BALLAST   v. PHILIPS ELECTRONICS


findings, as well as those that turn on witness credibility.
Id. Indeed, the Court has rejected the concurrence’s
reasoning with respect to Rule 52(a)(6), not only in its
case law, but also through its rulemaking. In 1985, Rule
52(a) was amended, in part, because
     [s]ome courts of appeal have stated that when a
     trial court’s findings do not rest on demeanor evi-
     dence and evaluation of a witness’[s] credibility,
     there is no reason to defer to the trial court’s find-
     ings and the appellate court more readily can find
     them to be clearly erroneous. See, e.g., Marcum v.
     United States, 621 F.2d 142, 144–45 (5th Cir.
     1980). Others go further, holding that appellate
     review may be had without application of the
     “clearly erroneous” test since the appellate court
     is in as good a position as the trial court to review
     a purely documentary record.
Fed. R. Civ. P. 52 advisory committee’s note (1985) (col-
lecting cases). The Advisory Committee continued:
     The principal argument advanced in favor of a
     more searching appellate review of findings by the
     district court based solely on documentary evi-
     dence is that the rationale of Rule 52(a) does not
     apply when the findings do not rest on the trial
     court’s assessment of credibility of the witnesses
     but on an evaluation of documentary proof and
     the drawing of inferences from it, thus eliminating
     the need for any special deference to the trial
     court’s findings. These considerations are out-
     weighed by the public interest in the stability and
     judicial economy that would be promoted by rec-
     ognizing that the trial court, not the appellate tri-
     bunal, should be the finder of facts. To permit
     courts of appeals to share more actively in the
     fact-finding function would tend to undermine the
LIGHTING BALLAST v. PHILIPS ELECTRONICS                        35


      legitimacy of the district courts in the eyes of liti-
      gants, multiply appeals by encouraging appellate
      retrial of some factual issues, and needlessly real-
      locate judicial authority.
Id.
    District court judges are provided training in all as-
pects of their duties, including claim construction in
patent litigation under Phillips. They then employ that
training repeatedly over the years, analyzing patents,
their written descriptions, and prosecution histories,
receiving testimony from inventors and experts, listening
to tutorials on the relevant science, and probing counsel
during hearings that sometimes last days. In this case,
the trial court conducted a three-day evidentiary hearing.
Because Cybor allows us to ignore these fact-intensive
inquiries by its insistence on de novo review, it not only
undermines the authority of district judges, it compromis-
es the decision-making process on appeal. Our court is
given free rein to interpret claim terms, but lacks the
resources to do it right. See Dunner & Kwon, supra, at
497 (noting that “the Federal Circuit, by function and
design, is ill-equipped to engage in the evidentiary evalu-
ations relevant to claim construction that are the staple of
district court judges”).
                               C.
    Cybor also creates greater incentives for losing parties
to appeal, thus discouraging settlements and increasing
the length and cost of litigation. As Judge Rader observed
in dissenting from the court’s pronouncements on claim
interpretation in Cybor, “unfettered review authority”
undercuts certainty and discourages settlement. 138 F.3d
at 1475. It is not until “the parties know the meaning of
the claims [that] they can predict with some reliability the
likelihood of a favorable judgment, factor in the economics
36                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


of infringement, and arrive at a settlement to save the
costs of litigation.” Id. But under Cybor, “the trial court’s
early claim interpretation provides no early certainty at
all, but only opens the bidding. The meaning of a claim
term is not certain (and the parties are not prepared to
settle) until nearly the last step of the process—decision
by the Court of Appeals for the Federal Circuit.” Id. at
1476; see also Amicus Br. of Prof. Peter Menell at 3 (la-
menting that Cybor “discourage[s] settlements following
claim construction and trial, delay[s] resolution of patent
disputes, and run[s] up the overall costs of patent litiga-
tion”); Amicus Br. of Am. Intellectual Prop. Ass’n at 8
(“Cybor thus fosters wasteful, expensive litigation and
discourages timely settlement. That result unnecessarily
ties up courts and increases expense to litigants.”); Ami-
cus Br. of Am. Bar Ass’n at 10–11 (observing that Cybor
discourages settlement); Amicus Br. of Ass’n of Bar of
N.Y. at 15–16 (same); Amicus Br. of Conn. Intellectual
Prop. L. Ass’n at 13 (“Even when a case goes to trial, the
losing party has very little incentive to settle disputes,
since there is a significant chance that at least some
material part of the trial court’s decision will be reversed
on appeal.”); Amicus Br. of Fed’n Internationale Des
Conseils en Propriete Intellectuelle at 11 (same); Amicus
Br. of Paul R. Michel at 4 (same). 7


     7  The majority cites data showing that a declining
percentage of cases proceed to trial or are appealed. See
Maj. Op. at 35–36. According to the majority, these
trends show that “the Cybor review procedure assists in
resolving litigation before full trial or extensive discov-
ery,” thereby facilitating settlement and reducing litiga-
tion costs. Id. at 36. Nothing suggests that these declines
can be attributed to this court’s de novo review of claim
construction, however. Declining trial and appeal rates
can easily be attributable to other factors, including (1)
LIGHTING BALLAST v. PHILIPS ELECTRONICS                  37


                            D.
    Contrary to the majority’s claim, moreover, Cybor
does not unqualifiedly promote uniformity or predictabil-
ity of outcome in the patent system. As noted previously,
the claim construction issues presented in patent cases
are mostly fact and case specific. A claim construction
decision in a given case will provide little guidance on the
words used in different patents. Their resolution will do
no more than declare the boundaries of a patent as be-
tween the parties in suit. See Blonder–Tongue Labs., Inc.
v. Univ. of Ill. Found., 402 U.S. 313, 329–30 (1971) (ob-
serving that “[s]ome litigants—those who never appeared
in a prior action—may not be collaterally estopped with-
out litigating [an] issue”). And, there is no guarantee that
panels of this court will construe like claims in a like
manner, even when in the same patent.              Compare

the availability of parallel proceedings at the PTO and
ITC where decisions in those tribunals might moot fur-
ther activity before the district courts, or even prevent
district court judgments from becoming final, (2) in-
creased resort to and availability of sophisticated alterna-
tive dispute resolution mechanisms, including the
increased involvement of retired district court judges with
patent litigation experience in such procedures, (3) im-
proved case management practices by trial judges who
have become more practiced at handling patent litigation
and who now often have the benefit of detailed local rules
governing the same, (4) the fact that, once this court
provided clear guidance regarding claim construction in
Phillips, trial courts were given a better roadmap for
undertaking the exercise of claim construction, and (5) the
increased experience and expertise of trial courts that
itself may be fostering settlements. The majority reads
far too much regarding the wisdom of Cybor into these
general statistics.
38                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


CVI/Beta Ventures, Inc. v. Custom Optical Frames, Inc.,
92 F.3d 1203 (Fed. Cir. 1996) (affirming the determina-
tion that “greater than 3% elasticity” did not require
“complete recovery after a strain of greater than 3%”
within the meaning of claim 1 of U.S. Patent No.
4,896,955), with CVI/Beta Ventures, Inc. v. Tura LP, 112
F.3d 1146, 1158 (Fed. Cir. 1997) (construing “greater than
3% elasticity” in claim 1 of U.S. Patent No. 4,896,955 as
requiring complete recovery after being subjected to
stress); see also Kimberly A. Moore, Are District Court
Judges Equipped to Resolve Patent Cases?, 15 Harv. J.L.
& Tech. 1, 18–21 (2001) (observing that “[t]he CVI/Beta
cases create doubt about whether the Federal Circuit
serves as a test of ‘accuracy’ of district court construc-
tion”).
    In fact, our case law expressly holds that we are not
bound by claim constructions we adopt on appeal from the
grant or denial of a preliminary injunction when consider-
ing the same claims again upon the final judgment. 8 See

     8   It is curious that, when reserving the right to
change our own claim constructions at later points in a
single case, we justify that position on grounds that the
greater fulsomeness of the record at the final judgment
stage better informs our claim construction analysis.
Transonic Sys., Inc. v. Non-Invasive Med. Techs. Corp., 75
F. App’x 765, 774 (Fed. Cir. 2003) (“A district court there-
fore is at liberty to change the construction of a claim
term as the record in a case evolves after a preliminary
injunction appeal.”); Jack Guttman, Inc. v. Kopykake
Enters., Inc., 302 F.3d 1352, 1361 (Fed. Cir. 2002) (“Dis-
trict courts may engage in a rolling claim construction, in
which the court revisits and alters its interpretation of
the terms as its understanding of the technology evolves.
This is particularly true where the issues involved are
complex, either due to the nature of the technology or
LIGHTING BALLAST v. PHILIPS ELECTRONICS                   39


Glaxo Grp. Ltd. v. Apotex, Inc., 376 F.3d 1339, 1346 (Fed.
Cir. 2004) (“An appellate court’s preliminary injunction
opinion has no conclusive bearing at the trial on the
merits and is not binding on a subsequent panel.” (citing
Univ. of Tex. v. Camenisch, 451 U.S. 390, 395 (1981));
Transonic Sys., Inc. v. Non-Invasive Med. Techs. Corp., 75
F. App’x 765, 774 (Fed. Cir. 2003) (“We have consistently
followed the Supreme Court’s precedent by holding that a
claim construction reached during an appeal from a grant
of a preliminary injunction is tentative and is not binding
on the district court in subsequent proceedings.”). We,
thus, do not even have an internal structure that unerr-
ingly assures uniformity.
    To the limited extent uniformity might be served by
de novo review, moreover, any marginal benefit from that
increased uniformity is more than offset by the decreased
certainty caused by making district court decisions more
vulnerable to reversal. See Kelly Casey Mullally, Legal
(Un)Certainty, Legal Process, and Patent Law, 43 Loy.
L.A. L. Rev. 1109, 1149–50 (2010) (examining how de
novo review increases one kind of certainty at the cost of
“mak[ing] district court judgments less certain” by “in-
creas[ing] the probability that the lower court’s decision
will be reversed”). And, as the PTO points out, “even if
some marginal decrease occurred in this Court’s ability to
ensure perfect uniformity in the interpretation of patent
claims, that decrease would not provide a reason to ignore
the clear mandate of Rule 52(a).” Amicus Br. of United
States at 12.

because the meaning of the claims is unclear from the
intrinsic evidence.” (citation omitted)). If the trial record
is effectively meaningless to the claim construction in-
quiry as we now hold, what more could we know about
claim construction later in a case than we knew when we
first visited it?
40                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


     We are not alone in the belief that Cybor does little to
promote the uniformity with which the majority is now
concerned. Indeed, “[i]n the government’s view, recali-
brating the standard of review to reflect the trial court’s
‘institutional advantage’ in considering certain types of
evidence in the claim-construction process, while preserv-
ing this Court’s ability to give de novo review to the trial
court’s ultimate construction, would promote ‘interjuris-
dictional uniformity.’” Amicus Br. of United States at 12–
13 (quoting Markman, 517 U.S. at 391). As several amici
explain, there are numerous other ways to improve uni-
formity of claim construction scope and interpretation,
including improvements to the patent prosecution pro-
cess, use of post-grant review procedures, or even consoli-
dation of cases addressing the same patents before a
single trial judge through the already well-established
multidistrict litigation practice. See, e.g., Amicus Br. of
Prof. Peter Menell at 22–24. And, as the American Bar
Association notes, it is more likely that uniformity will be
served by greater reliance on the claim construction
decisions of the skilled fact finders—the district court
judges—than by adhering to Cybor’s de novo standard of
review. Amicus Br. at 13.
    Our case law teaches that stare decisis is not an ob-
stacle when our law causes such negative consequences.
The recent decision by our en banc court in Therasense,
Inc. v. Becton, Dickinson & Co., 649 F.3d 1276 (Fed. Cir.
2011) (en banc), is a clear example of this court’s willing-
ness to change our law where, as here, experience proves
our past decisions were unwise. In Therasense, this court
made drastic changes to the law with the aim of making
claims of inequitable conduct more difficult to prove. See
id. at 1290–91. In explaining why we did so, we noted
that, over the years, we had “embraced . . . reduced
standards for intent and materiality to foster full disclo-
sure to the PTO.” Id. at 1288. But, “[t]his focus on en-
LIGHTING BALLAST v. PHILIPS ELECTRONICS                41


couraging disclosure had numerous unforeseen and
unintended consequences.” Id. Given the negative effects
of our precedent, we wholly abrogated our decisions in
Orthopedic Equipment Co. v. All Orthopedic Appliances,
Inc., 707 F.2d 1376 (Fed. Cir. 1983), Driscoll v. Cebalo,
731 F.2d 878 (Fed. Cir. 1984), and American Hoist &
Derrick Co. v. Sowa & Sons, Inc., 725 F.2d 1350 (Fed. Cir.
1984), and required a greater showing to demonstrate
inequitable conduct. Even the dissent in Therasense had
no problem with abrogating our body of case law on
inequitable conduct, disputing only what new test should
be adopted in its stead. See Therasense, 649 F.3d at 1302
(Bryson, J., dissenting) (urging adoption of a new stand-
ard, but one that differed from that proposed by the
majority).
    Likewise, in Knorr–Bremse Systeme Fuer Nutzfahr-
zeuge GmbH v. Dana Corp., 383 F.3d 1337 (Fed. Cir.
2004) (en banc), we overturned case law because we felt it
had problematic effects. There, we observed that “imple-
mentation of [our prior] precedent has resulted in inap-
propriate burdens on the attorney-client relationship.”
383 F.3d at 1343. Looking at the full range of conse-
quences flowing from our case law, we concluded that “the
conceptual underpinnings of this precedent have signifi-
cantly diminished in force.” Id. at 1344 (citation and
internal quotation marks omitted). So, we changed the
law. Id. (“The adverse inference that an opinion was or
would have been unfavorable, flowing from the infringer’s
failure to obtain or produce an exculpatory opinion of
counsel, is no longer warranted. Precedent authorizing
such inference is overruled.”).
    Thus, we have made clear that stare decisis does not
prevent our court from changing our law where, as here,
there are compelling reasons to do so.
42                 LIGHTING BALLAST   v. PHILIPS ELECTRONICS


                           VII.
    In short, while Markman instructs us that claim con-
struction presents a question for the court to resolve, it
also instructs us that claim construction is a “mongrel
practice,” presenting a mixed question of law and fact.
While we agree that the ultimate question of claim mean-
ing should remain subject to de novo review, claim con-
struction often requires district courts to resolve
underlying issues of disputed fact. These include, among
others: whether a claim term had a specialized meaning
among those skilled in the art at the time; what texts,
including treatises and dictionaries, demonstrate about
how a person of skill in the art would interpret a claim
term, and which contemporaneous tests are most rele-
vant; whether to credit one expert’s testimony over anoth-
er’s regarding issues bearing on claim construction; who
qualifies as a person of ordinary skill in the art; what is
the relevant field of invention; what prior art is relevant;
what a person of skill in the art would glean from that
prior art; and what inferences can be fairly drawn from
the prosecution history, including whether a disclaimer of
claim scope has occurred. 9 When a district court makes
fact-findings needed to resolve claim construction dis-


     9  Notably, a district court’s factual determinations,
even those about the historical meaning of a claim term,
will not resolve the legal question of what construction is
to be afforded a claim term. This court would be free to
conclude that a claim term has a different meaning than
its historically common one based on the four corners of
the patent itself, or on application of legal doctrines
applicable to claim construction such as claim differentia-
tion, meanings we have subscribed to common terms (e.g.,
“comprising”), or the concept of an inventor being permit-
ted to act as his own lexicographer.
LIGHTING BALLAST v. PHILIPS ELECTRONICS                 43


putes, Rule 52(a) requires us to defer to those findings
unless they are clearly erroneous.
     Cybor ignores both the realities of claim construction
and Rule 52(a)’s demands. It is time we acknowledge the
limitations of our appellate function and our obligation to
comply with the Federal Rules of Civil Procedure, and
give trial judges the deference their expertise and efforts
deserve. Stare decisis is no bar to our doing so. Nor is
concern about the fact that employing the proper stand-
ard of review in this context will not always be easy. For
all these reasons, I respectfully dissent.
