  United States Court of Appeals
      for the Federal Circuit
                ______________________

               G. DAVID JANG, M.D.,
                  Plaintiff-Appellant

                           v.

 BOSTON SCIENTIFIC CORPORATION, SCIMED
 LIFE SYSTEMS, INC., NKA BOSTON SCIENTIFIC
                SCIMED, INC.,
           Defendants-Cross-Appellants
             ______________________

                 2016-1275, 2016-1575
                ______________________

   Appeals from the United States District Court for the
Central District of California in No. 5:05-cv-00426-VAP-
MRW, Judge Virginia Anne Phillips.
                 ______________________

             Decided: September 29, 2017
               ______________________

    DARYL JOSEFFER, King & Spalding LLP, Washington,
DC, argued for plaintiff-appellant. Also represented by
JED I. BERGMAN, Kasowitz, Benson, Torres & Friedman
LLP, New York, NY; MARCUS BARBER, DARCY L. JONES,
HEATHER KIM, JONATHAN K. WALDROP, Redwood Shores,
CA; JEFFREY J. TONEY, PAUL GUNTER WILLIAMS, Atlanta,
GA.
2            JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



    MATTHEW WOLF, Arnold & Porter Kaye Scholer LLP,
Washington, DC, argued for defendants-cross-appellants.
Also represented by EDWARD HAN, JOHN NILSSON.
                 ______________________

 Before PROST, Chief Judge, O’MALLEY and CHEN, Circuit
                        Judges.
CHEN, Circuit Judge.
     This dispute between G. David Jang, M.D. (Dr. Jang)
and Boston Scientific Corp. and Scimed Life Systems, Inc.
(collectively, BSC), more than a decade old, returns to us
for a fourth time. In the latest appeal of this case involv-
ing U.S. Patent No. 5,922,021 (ʼ021 Patent) and BSC’s
sales of several coronary stents (collectively, Express
stent), Dr. Jang challenges the district court’s denial of
his motion for judgment as a matter of law (JMOL) on the
ground that no reasonable jury could have found that
BSC’s Express stent did not literally infringe claims 1 and
8 (the asserted claims) of the ’021 Patent. Dr. Jang also
challenges the district court’s vacatur of the jury’s finding
that the Express stent infringed the asserted claims
under the doctrine of equivalents, as well as the entry of
judgment of non-infringement in favor of BSC, on the
ground that the district court incorrectly held that he
failed to provide an acceptable hypothetical claim for an
ensnarement analysis, and thereby failed to prove that
his doctrine of equivalents theory did not ensnare the
prior art. Dr. Jang’s appeal is accompanied by a purport-
ed cross-appeal from BSC, which assigns error to the
district court’s holding that BSC was contractually obli-
gated to pay royalties for past sales of the Express stent if
it infringed the asserted claims, notwithstanding the U.S.
Patent and Trademark Office’s (PTO) eventual cancella-
tion of them in an ex parte reexamination.
   Because we affirm the district court’s denial of Dr.
Jang’s motion for JMOL, its vacatur of the jury verdict of
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.           3



infringement under the doctrine of equivalents, and its
entry of judgment of non-infringement, we dismiss BSC’s
cross-appeal and need not reach the arguments it raised.
                       INTRODUCTION
                    A. The ’021 Patent
    Dr. Jang is the named inventor of the ’021 Patent,
which is generally directed to a coronary stent. A repre-
sentative embodiment of the claimed stent is below.




’021 Patent fig. 9D (annotated). Inside the dotted boxes
are expansion columns made up of a plurality of pairs of
expansion struts. The solid box outlines a connecting
strut column made up of connecting struts. Each connect-
ing strut has: (i) a section at the “proximal” end that
connects to an expansion strut pair in one expansion
column; (ii) a section at the “distal” end that connects to
an expansion strut pair in another expansion column; and
(iii) an intermediate section that is not parallel to the two
end sections. See, e.g., id. col. 13 ll. 5–18, 38–48. Given
4             JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



the connecting strut’s proximal and distal connections,
each connecting strut links expansion strut pairs from
two expansion columns in a “peak-to-peak” configuration.
The connecting struts are designed to increase the longi-
tudinal flexibility of the stent. See id. col. 6 ll. 29–36; id.
col. 8 ll. 45–47.
    Independent claim 1 is representative of the asserted
claims:
    1. A stent in a non-expanded state, comprising:
    a first expansion strut pair including a first ex-
    pansion strut positioned adjacent to a second ex-
    pansion strut and a joining strut of the first
    expansion strut pair that couples the first and
    second expansion struts at a distal end of the first
    expansion strut pair, a plurality of the first expan-
    sion strut pair forming a first expansion column;
    a second expansion strut pair including a first ex-
    pansion strut positioned adjacent to a second ex-
    pansion strut and a joining strut of the second
    expansion strut pair that couples the first and
    second expansion struts of the second expansion
    strut pair at a proximal end of the second expan-
    sion strut pair, a plurality of the second expansion
    strut pair forming a second expansion column;
    a first connecting strut including a first connect-
    ing strut proximal section, a first connecting strut
    distal section and a first connecting strut inter-
    mediate section, the first connecting strut proxi-
    mal section being coupled to the distal end of the
    first expansion strut pair in the first expansion
    column and the first connecting strut distal sec-
    tion being coupled to the proximal end of the sec-
    ond expansion strut pair of the second expansion
    column, a plurality of the first connecting strut
    forming a first connecting strut column that cou-
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.          5



    ples the first expansion column to the second ex-
    pansion column, the first connecting strut inter-
    mediate section being nonparallel to the first
    connecting strut proximal and distal sections,
    wherein the first expansion strut of the first ex-
    pansion strut pair in the first expansion column
    has a longitudinal axis offset from a longitudinal
    axis of the first expansion strut of the second ex-
    pansion strut pair in the second expansion col-
    umn.
Id. col. 18 ll. 9–40 (emphases added). 1
                  B. BSC’s Express Stent
    The Express stent comprises two types of alternating
columns or “elements”—referred to as “macroelements”
and “microelements”—that are joined together. Micro-
elements, depicted inside the box in the schematic below,
are smaller and narrower than the macroelements on
either side of the microelements. The microelements
include horizontal bars that join the microelements and
the macroelements together in a “peak-to-valley” configu-
ration.




    1   As our previous opinion recognized, the PTO can-
celled asserted claims 1 and 8 on February 11, 2014 in a
second ex parte reexamination. Jang v. Boston Sci. Corp.,
767 F.3d 1334 (Fed. Cir. 2014). Because we affirm the
district court’s non-infringement determination, and
therefore need not address BSC’s cross appeal, the PTO’s
cancellation of claims 1 and 8 has no bearing in our
decision.
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.         7



2013, BSC requested an ex parte reexamination of the
asserted claims before the PTO.
    In conjunction with its reexamination request, BSC
sought leave to amend its answer to include invalidity
defenses, under the theory that the assignment agree-
ment should be interpreted so as to relieve BSC of any
obligation to pay royalties for already-made sales of its
Express stent, if the asserted claims were determined to
be invalid or unpatentable. See J.A. at 6091. The district
court denied BSC leave to amend, deeming any invalidity
defenses “irrelevant” as to whether BSC owed Dr. Jang
royalties for past sales under the terms of the assignment
agreement. Id. The district court reasoned that BSC’s
interpretation of the assignment agreement “would lead
to an absurd result, namely, that BSC could avoid pay-
ment . . . under the [a]greement, even if the [’021 Patent]
[were] declared invalid years after the [royalty] payments
were due.” Id.
    BSC then moved for summary judgment using the
same tack after the PTO cancelled the asserted claims as
unpatentable in the ex parte reexamination. See id. at
50–56. BSC contended that it owed Dr. Jang no royalties
under the assignment agreement even if they had accrued
well before the cancellation because unpatentable claims
cannot be infringed. See id. at 50. The district court
denied summary judgment, holding that BSC still owed
royalties to Dr. Jang for any past sales of stents covered
by the asserted claims under the assignment agreement,
despite the PTO’s subsequent cancellation of those claims.
See id. at 50–56.
    The parties then proceeded to trial as to whether the
Express stent infringed the asserted claims of the ’021
Patent. Before trial, BSC moved in limine to preclude Dr.
Jang from presenting a doctrine of equivalents theory to
the jury, accusing him of merely rehashing his literal
infringement theory in the guise of a doctrine of equiva-
8            JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



lents theory, and thus, failing to provide particularized
testimony as to how the Express stent is insubstantially
different than the asserted claims. See id. at 66–69. The
district court denied the motion, finding that Dr. Jang’s
experts, Michael J. Lee and Nicolas A.F. Chronos, M.D.,
sufficiently explained his doctrine of equivalents theory in
their expert reports. See id. at 68–69.
    Collateral to this motion in limine was BSC’s invoca-
tion of an ensnarement defense. See id. at 9–12. BSC
insisted that Dr. Jang’s doctrine of equivalents theory
would ensnare the prior art, referencing three prior art
patents. See id. at 11. The district court decided to
conduct a post-trial ensnarement hearing, if the jury
returned a verdict of infringement under the doctrine of
equivalents. See id. at 12207.
     The jury ultimately found no literal infringement, but
found infringement under the doctrine of equivalents.
Following through on its earlier decision, the district
court conducted an evidentiary hearing on ensnarement.
Dr. Jang objected, asserting that BSC belatedly raised
ensnarement, and thus waived it. See id. at 9–12; see also
id. at 34. The district court found no waiver. See id. at 9–
12.
     On the merits of the ensnarement inquiry, Dr. Jang
elected to use a hypothetical claim analysis to establish a
range of equivalents to which he believed he was entitled,
above and beyond the actual scope of his asserted claims.
See id. at 12–19. In other words, he attempted to con-
struct a hypothetical claim—predicated on representative
claim 1—that would be broad enough to literally cover
BSC’s Express stent, yet not so broad that it would be
unpatentable over the prior art. See, e.g., Intendis GmbH
v. Glenmark Pharm. Inc., USA, 822 F.3d 1355, 1363–64
(Fed. Cir. 2016). In the course of trying to draft such a
hypothetical claim, Dr. Jang constructed approximately
ten different claims, and ultimately chose to assert two of
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.          9



them: hypothetical claim three and hypothetical claim
five. See J.A. at 14–19. The district court concluded,
however, that Dr. Jang failed, as a threshold matter, to
draft a proper hypothetical claim for the ensnarement
analysis. See id. The district court rejected hypothetical
claim three because it impermissibly narrowed claim 1
and hypothetical claim five because it failed to broaden
claim 1 at all. See id. Because Dr. Jang did not meet his
burden of persuasion, which includes providing a proper
hypothetical claim that does not ensnare the prior art, the
district court vacated the jury verdict of infringement
under the doctrine of equivalents and entered judgment of
non-infringement in favor of BSC. See id. at 18–19.
    Dr. Jang then moved for JMOL with respect to, inter
alia, literal infringement. See id. at 23–32. The district
court found substantial evidence to support the jury’s
verdict of no literal infringement, concluding that the jury
could have reasonably found either that the Express
stent’s microelements corresponded to the claimed expan-
sion columns rather than the claimed connecting strut
columns or that the Express stent’s macroelement (first
expansion column) was connected to the microelement
(second expansion column) in a “peak-to-valley” configura-
tion instead of a “peak-to-peak” configuration. See id. at
27. Dr. Jang also moved for a new trial, asserting several
bases, all of which the district court rejected. See id. at
33–35.
    Dr. Jang appeals the district court’s denial of his
JMOL for literal infringement, as well as his motion for a
new trial, and its vacatur of the jury verdict of infringe-
ment under the doctrine of equivalents. BSC purports to
cross-appeal the district court’s denial of its summary
judgment motion. We have jurisdiction over Dr. Jang’s
appeal pursuant to 28 U.S.C. § 1295 (a)(1) (2012).
10           JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



                       DISCUSSION
                 A. Literal Infringement
    The parties do not dispute that the Express stent’s
macroelements literally meet all expansion column-
related limitations of claim 1, leaving them to contest only
whether the jury had a reasonable basis to find that the
Express stent’s microelements do not meet all connecting
strut-related limitations in the claim. Dr. Jang maintains
that a reasonable jury could not have found no literal
infringement in this limited context because the undis-
puted facts showed otherwise and BSC’s non-
infringement arguments were legally erroneous. At the
very least, according to Dr. Jang, he is entitled to a new
trial that is not tainted with the legally erroneous argu-
ments. We disagree with Dr. Jang’s arguments.
     Denials of motions for JMOL or a new trial are re-
viewed according to the law of the regional circuit—here,
the Ninth Circuit. See, e.g., TVIIM, LLC v. McAfee, Inc.,
851 F.3d 1356, 1362 (Fed. Cir. 2017). A district court’s
denial of a motion for JMOL is reviewed de novo. See,
e.g., id. (citing Harper v. City of Los Angeles, 533 F.3d
1010, 1021 (9th Cir. 2008)). A grant of a motion for JMOL
is proper only when “the evidence, construed in the light
most favorable to the nonmoving party, permits only one
reasonable conclusion, and that conclusion is contrary to
that of the jury.” White v. Ford Motor Co., 312 F.3d 998,
1010 (9th Cir. 2002) (quoting Forrett v. Richardson, 112
F.3d 416, 419 (9th Cir. 1997)). That is, the district court
must uphold a jury’s verdict “if it is supported by substan-
tial evidence, which is evidence adequate to support the
jury’s conclusion, even if it is also possible to draw a
contrary conclusion.” Harper, 533 F.3d at 1021 (quoting
Pavao v. Pagay, 307 F.3d 915, 918 (9th Cir. 2002)). Sub-
stantial evidence is “such relevant evidence as a reasona-
ble mind might accept as adequate to support a
conclusion.” Theme Promotions, Inc. v. News Am. Mktg.
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.          11



FSI, 546 F.3d 991, 1000 (9th Cir. 2008) (quoting Syufy
Enters. v. Am. Multicinema, Inc., 793 F.2d 990, 992 (9th
Cir. 1986)).
    The Ninth Circuit reviews the denial of a motion for a
new trial for abuse of discretion. Incalza v. Fendi N. Am.,
Inc., 479 F.3d 1005, 1013 (9th Cir. 2007). It reverses the
denial only if the record lacks any evidence supporting the
verdict or if the district court made a mistake of law.
Molski v. M.J. Cable, Inc., 481 F.3d 724, 729 (9th Cir.
2007).
    Dr. Jang contends that the district court erred in
denying his motion for JMOL because it failed to consider
whether Dr. Jang proved that the Express stent’s micro-
elements were connecting strut columns, notwithstanding
the fact that they may also be expansion columns. In
other words, that there was sufficient evidence for the
jury to find that the Express stent’s microelements were
expansion columns is irrelevant to the resolution of his
motion for JMOL, Dr. Jang argues, so long as he showed
that the microelements were connecting strut columns.
See Appellant Br. at 55 (“If the [microelements] satisfy
the claim terms of a connecting-strut column, then they
are connecting-strut columns for literal infringement
purposes, regardless of whether they might also be con-
sidered something else (such as expansion columns).”).
Dr. Jang also maintains that the district court erred in
denying his motion for JMOL because BSC’s arguments
rest on legally erroneous premises and so they cannot
support the jury’s verdict of no literal infringement.
    The issue of literal infringement was a question of
fact for the jury. The jury heard Dr. Jang’s theory of
infringement and his supporting evidence but neverthe-
less found that the Express stent did not literally infringe.
The district court did not fail to consider Dr. Jang’s theory
of infringement and it correctly found substantial evi-
dence to support the jury’s finding that the Express
12           JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



stent’s microelements do not literally meet the connect-
ing-strut-column-related limitations in claim 1. See J.A.
at 25–28. BSC’s expert, James Moore, Ph.D., testified
that the Express stent’s macroelements and the micro-
elements were more akin to the claimed expansion col-
umns than the claimed connecting strut columns in the
asserted claims because both elements expand the Ex-
press stent when needed, which causes foreshortening of
the stent. See id. at 9330–43, 9389–90. These elements
stood in contrast to the claimed connecting strut columns
that do not expand when the claimed stent expands, and
instead, compensate for the foreshortening caused by the
expansion of the claimed expansion columns. See id.
Moreover, the Express stent’s macroelements and micro-
elements are joined together in a “peak-to-valley” configu-
ration by a connecting strut with a parallel intermediate
section, i.e., a straight, horizontal connector—as opposed
to the claimed expansion columns that are joined in a
“peak-to-peak” configuration by a connector with a non-
parallel intermediate section. 3 See id. Dr. Jang’s experts
conceded as much. See id. at 8877–79 (Mr. Lee acknowl-
edging that the Express stent’s microelements could be
expansion columns); id. at 8869–73 (Mr. Lee recognizing
that the Express stent’s microelements and macroele-
ments could be viewed as being joined by straight con-
nectors); id. at 9260–61 (Dr. Chronos acknowledging that
the Express stent’s microelements behave like expansion
columns); id. at 9284–85 (Dr. Chronos recognizing that if
the Express stent’s microelements and macroelements are
viewed as expansion columns, then they are joined by a
straight connector). The jury’s verdict of no literal in-
fringement, therefore, is supported by substantial evi-
dence.


     3  Despite the fact that the asserted claims do not
use the term “peak-to-peak,” the parties agree that this is
an inherent limitation of the asserted claims.
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.         13



    Dr. Jang failed to persuade the district court that
BSC’s non-infringement arguments were legally errone-
ous. We are similarly unpersuaded. Dr. Jang character-
izes BSC’s position as one of mutual exclusivity and
argues that this purported “‘either/or’ position effectively
imported a negative limitation into the definition of
‘connecting strut column.’” Appellant Reply Br. at 33. Dr.
Jang misrepresents BSC’s non-infringement arguments.
BSC did not argue, as Dr. Jang contends, that microele-
ments could only be deemed either exclusively expansion
columns or exclusively connecting strut columns. Rather,
BSC fairly argued at trial that the microelements, like the
macroelements, simply are expansion columns. J.A. at
8413–14, 10573. In particular, BSC argued that there
was no literal infringement because those two expansion
columns are joined by straight connectors in a peak-to-
valley configuration. Id. at 10570, 11366.
    Dr. Jang also contends that BSC misled the jury to
find no literal infringement because BSC told the jury
that the Express stent’s microelements could not be the
claimed connecting strut columns due to the presence of
“extra metal” in the microelements that is not recited in
the asserted claims. This was erroneous according to Dr.
Jang because the asserted claims use the transitional
phrase “comprising,” i.e., open-ended claim language, and
so the addition of “extra metal” in the Express stent
cannot preclude a finding of literal infringement. But this
was not one of BSC’s non-infringement positions at trial.
To the extent that BSC introduced this “extra metal”
concept to the jury, BSC did so, not as an alternative non-
infringement position, but as an explanation that Dr.
Jang’s experts ignored certain structural features of the
Express stent in their infringement analyses, thereby
undermining the strength of their testimony on whether
the microelements were connecting strut columns. See id.
at 9343, 10579–80.
14           JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



   In sum, a reasonable jury could have returned a ver-
dict of no literal infringement based on the evidence
presented at trial. We consequently have no basis to
order a new trial.
     B. Ensnarement in View of a Hypothetical Claim
    In an appeal relating to the doctrine of equivalents, a
party often challenges the fact finding made below of
infringement (or no infringement) under that doctrine,
which is usually analyzed under the well-established
“substantially the same function-way-result” or “insub-
stantial differences” inquiry. Here, however, the jury’s
finding that the Express stent satisfies each claim ele-
ment of the asserted claims under the doctrine of equiva-
lents is not on appeal. Instead, this appeal centers on the
district court’s application of a limitation on the reach of
the doctrine, known as “ensnarement.”
    Dr. Jang insists that the district court erred in several
respects in overturning the jury’s verdict of infringement
under the doctrine of equivalents based on BSC’s en-
snarement defense. Dr. Jang argues that his hypothetical
claims three and five are properly broader in scope than
representative claim 1, and if they were flawed, the
district court was required to proceed with an ensnare-
ment analysis, even if that meant the district court would
have to devise an acceptable hypothetical claim for Dr.
Jang that was broader in scope than representative claim
1. Dr. Jang is wrong on both counts.
    A doctrine of equivalents theory cannot be asserted if
it will encompass or “ensnare” the prior art. DePuy Spine,
Inc. v. Medtronic Sofamor Danek, Inc., 567 F.3d 1314,
1322 (Fed. Cir. 2009). “This limitation is imposed even if
a jury has found equivalence as to each claim element.”
Id. at 1323 (citing Wilson Sporting Goods Co. v. David
Geoffrey & Assocs., 904 F.2d 677, 683, 687 (Fed. Cir.
1990), overruled in part on other grounds, Cardinal Chem.
Co. v. Morton Int’l, Inc., 508 U.S. 83, 92 n.12 (1993)). A
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.            15



“[h]ypothetical claim analysis is a practical method to
determine whether an equivalent would impermissibly
ensnare the prior art.” 4 Intendis, 822 F.3d at 1363–64
(citing Ultra-Tex Surfaces, Inc. v. Hill Bros. Chem. Co.,
204 F.3d 1360, 1364 (Fed. Cir. 2000)). We have explained:
    Hypothetical claim analysis is a two-step process.
    The first step is “to construct a hypothetical claim
    that literally covers the accused device.” Next,
    prior art introduced by the accused infringer is
    assessed to “determine whether the patentee has
    carried its burden of persuading the court that the
    hypothetical claim is patentable over the prior
    art.” In short, [the court] ask[s] if a hypothetical
    claim can be crafted, which contains both the lit-
    eral claim scope and the accused device, without
    ensnaring the prior art.
Id. at 1363 (quoting DePuy, 567 F.3d at 1324, 1325); see
also Ultra-Tex Surfaces, 204 F.3d at 1364–65 (“Under a
hypothetical claim analysis, a patentee proposes a hypo-
thetical claim that is sufficiently broad in scope to literally
encompass the accused product or process. If that claim
would have been allowed by the PTO over the prior art,
then the prior art does not bar the application of the
doctrine of equivalents.” (citations omitted)). “The burden
of producing evidence of prior art to challenge a hypothet-
ical claim rests with an accused infringer, but the burden


    4   The hypothetical claim analysis is not the only
method in which a district court can assess whether a
doctrine of equivalents theory ensnares the prior art. See
Conroy v. Reebok Int’l, Ltd., 14 F.3d 1570, 1576–77 (Fed.
Cir. 1994); Int’l Visual Corp. v. Crown Metal Mfg. Co., 991
F.2d 768, 772 (Fed. Cir. 1993). We note that Dr. Jang
never asked the district court to assess the scope of his
doctrine of equivalents theory using a method other than
the hypothetical claim analysis.
16            JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



of proving patentability of the hypothetical claim rests
with the patentee.” 5 Interactive Pictures Corp. v. Infinite
Pictures, Inc., 274 F.3d 1371, 1380 (Fed. Cir. 2001) (citing
Streamfeeder, LLC v. Sure-Feed, Inc., 175 F.3d 974, 984
(Fed. Cir. 1999)). “We review a district court’s conclusion
that a hypothetical claim does not encompass the prior art
de novo and resolution of underlying factual issues for
clear error.” Intendis, 822 F.3d at 1363 (citing DePuy, 567
F.3d at 1324).
    The district court correctly concluded that Dr. Jang’s
hypothetical claims three and five were flawed and
properly declined to conduct any hypothetical claim
analysis as a result. See J.A. at 12–19. Dr. Jang’s hypo-
thetical claim three reads:
     the first connecting strut intermediate section be
     ing non parallel to the first connecting strut prox
     imal and distal sections column configured to
     provide increased flexibility compared to the first
     and second expansion columns.
Id. at 14 (strikethrough and emphasis to reflect amend-
ments to claim 1). 6 Although hypothetical claim three is
broader than claim 1 by deleting the non-parallel inter-
mediate section limitation (thereby encompassing con-
necting struts with a parallel intermediate section), it also



     5  We have described the ensnarement inquiry as
one of determining the patentability of the hypothetical
claim, rather than its validity. That is because “[t]he
pertinent question” is “whether that hypothetical claim
could have been allowed by the PTO over the prior art” as
the PTO has never actually issued it. Wilson Sporting
Goods, 904 F.2d at 684.
    6   We will not recite the other limitations of claim 1
that remain unchanged in Dr. Jang’s hypothetical claims
three and five.
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.         17



is narrower by adding the requirement that the connect-
ing strut column must provide more flexibility as com-
pared to the expansion columns. Our precedent has been
clear, however, that a patentee’s hypothetical claim may
not add any narrowing limitations. See Streamfeeder, 175
F.3d at 983 (“While use of a hypothetical claim may
permit a minor extension of a claim to cover subject
matter that is substantially equivalent to that literally
claimed, one cannot, in the course of litigation and outside
of the PTO, cut and trim, expanding here, and narrowing
there, to arrive at a claim that encompasses an accused
device, but avoids the prior art. Slight broadening is
permitted at that point, but not narrowing.”). Whereas
claim 1 previously covered embodiments where the con-
necting strut column has the same or lesser degree of
flexibility when compared to the first and second expan-
sion columns, hypothetical claim three narrows claim 1
so that the connecting strut column must have an in-
creased degree of flexibility when compared to the first
and second expansion columns. See J.A. at 16. The
district court thus correctly rejected Dr. Jang’s hypothet-
ical claim three.
    Dr. Jang contends that the combination of the added
comparative flexibility limitation with the deletion of the
non-parallel intermediate section limitation results in an
overall broader claim scope than claim 1, because, in his
view, the comparative flexibility limitation recites the
function that the non-parallel intermediate section of the
connecting strut is designed to achieve. In other words,
Dr. Jang argues that he simply is replacing a structural
limitation for a functional limitation that encompasses
the structural limitation, as well as all other structures
that perform that function. But this argument is prob-
lematic because nothing in the ’021 Patent or elsewhere
in the record indicates that the claimed connecting strut
columns provide increased flexibility in comparison to the
claimed expansion columns. Although the specification
18            JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



explains that the connecting strut columns improve a
particular form of flexibility (i.e., longitudinal) of the stent
as a whole, see ’021 Patent col. 6 ll. 29–36; id. col. 8 ll. 45–
47, it never discusses the flexibility of the connecting strut
columns vis-à-vis the expansion columns. We thus cannot
agree with Dr. Jang that the limitation he added in
hypothetical claim three is merely a broader version of
the limitation he deleted from claim 1.
     As for Dr. Jang’s hypothetical claim five, it reads:
     a first connecting strut including at least a first
     connecting strut proximal section, a first connect-
     ing strut distal section and a first connecting strut
     intermediate section[.]
J.A. at 17 (emphasis to reflect amendment to claim 1).
This hypothetical claim does not broaden claim 1 at all.
Claim 1 already uses the transitional phrase “comprising”
to establish an open-ended claim. See, e.g., Vehicular
Techs. Corp. v. Titan Wheel Int’l, Inc., 212 F.3d 1377,
1383–84 (Fed. Cir. 2000) (“A drafter uses the term ‘com-
prising’ to mean ‘I claim at least what follows and poten-
tially more.’”).   Thus, the addition of “at least” to
hypothetical claim five is redundant with claim 1’s recita-
tion of “comprising.” In short, hypothetical claim five and
claim 1 have the same claim scope.
    Following Dr. Jang’s troubles in drafting a proper
hypothetical claim that encompassed the Express stent
yet was also patentable in the face of seemingly crowded
prior art (a venture that began with generating approxi-
mately ten different hypothetical claims), the district
court was under no obligation to undertake a hypothetical
claim analysis on his behalf. A patentee, like Dr. Jang,
bears the burden of proving that it is entitled to “the
range of equivalents which it seeks.” Wilson Sporting
Goods, 904 F.2d at 685. And, when utilizing the hypo-
thetical claim tool, that burden starts with proposing a
proper hypothetical claim that only broadens the issued
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.         19



asserted claims. See Streamfeeder, 175 F.3d at 983. Dr.
Jang cannot effectively transfer the responsibility of
defining the range of equivalents to which he is entitled to
the district court. 7 See Ultra-Tex Surfaces, 204 F.3d at
1364 (“Under a hypothetical claim analysis, a patentee
proposes a hypothetical claim . . . .” (emphasis added)).
Because, as a threshold matter, Dr. Jang failed to submit
a proper hypothetical claim for consideration, he was
unable to meet his burden of proving that his doctrine of
equivalents theory did not ensnare the prior art. The
district court thus correctly vacated the jury verdict of
infringement under the doctrine of equivalents.
    Failing on the merits, Dr. Jang turns to several pur-
ported procedural infirmities in the district court’s han-
dling of BSC’s ensnarement defense. Dr. Jang specifically
argues that BSC waived its ensnarement defense because:
(1) BSC failed to raise the defense in a motion for either
summary judgment or JMOL; (2) the defense was a proxy
for invalidity defenses that were excluded by the district
court earlier in the case; (3) BSC’s belated notice to Dr.
Jang of the defense was prejudicial because it deprived
him of any pre-trial discovery related to the defense; and
(4) the defense was never listed in the pretrial order as
required by Ninth Circuit law. We address each of these
unpersuasive arguments in turn.



    7    In Streamfeeder, after we rejected the patentee’s
hypothetical claim for impermissibly narrowing the
patent claim in one respect while also broadening it in
another, we additionally explained why a proper hypo-
thetical claim in that case—one without the narrowing
limitation—was unpatentable over the prior art. See 175
F.3d at 983–84. Nothing in Streamfeeder, however,
requires courts to engage in this additional inquiry when
the patentee fails to come forward with a proper hypothet-
ical claim.
20            JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



    First, Dr. Jang argues that in DePuy we held that
ensnarement must be raised in a motion for either sum-
mary judgment or JMOL. See Appellant Br. at 30 (citing
DePuy, 567 F.3d at 1324). But that is an unduly narrow
reading of DePuy. We considered in that case whether
ensnarement is a factual question that must be tried to
the jury. 567 F.3d at 1323. To answer that question, we
turned to precedent, which has treated ensnarement and
prosecution history estoppel on equal footing. See id.
(“We have called ensnarement and prosecution history
estoppel, collectively, ‘two policy oriented limitations’ on
the doctrine of equivalents, both of which are ‘applied as
questions of law.’” (quoting Loctite Corp. v. Ultraseal Ltd.,
781 F.2d 861, 870 (Fed. Cir. 1985), overruled in part on
other grounds, Nobelpharma AB v. Implant Innovations,
Inc., 141 F.3d 1059, 1068 (Fed. Cir. 1998) (en banc)).
Because prosecution history estoppel was a legal question
for a district court to consider, we concluded that en-
snarement was one as well. See id. (“We see no reason
why ensnarement should be treated differently, for proce-
dural purposes, than prosecution history estoppel.”). We
held that
     [E]nsnarement, like prosecution history estoppel,
     is “to be determined by the court, either on a pre-
     trial motion for partial summary judgment or on a
     motion for judgment as a matter of law at the
     close of the evidence and after the jury verdict.”
     As a practical matter, both legal limitations may
     be readily addressed in the same set of motions.
Id. at 1324 (quoting Warner-Jenkinson Co. v. Hilton Davis
Chem. Co., 520 U.S. 17, 39 n.8 (1997)). Our “holding” in
DePuy was not that these two motions were the only
vehicles by which to raise ensnarement. Instead, when
read in context, DePuy is most fairly understood as hold-
ing that ensnarement is a legal question for the district
court to decide and that the district court could, but did
not have to, decide that question through particular types
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.          21



of motions. See id. This is especially so because the
district court in DePuy conducted a separate ensnarement
proceeding after a jury verdict of infringement under the
doctrine of equivalents, just as the district court did here.
See id. at 1321–22. We see nothing legally unsound in
BSC raising ensnarement through its pretrial motion in
limine, and the district court conducting a post-trial
hearing on the defense contingent on an infringement
verdict under the doctrine of equivalents. Moreover,
based on a review of the record, we are satisfied that Dr.
Jang received sufficient notice of BSC’s ensnarement
argument.
    Second, Dr. Jang argues that the district court should
have barred BSC from presenting its ensnarement de-
fense as a matter of law because BSC was not allowed to
challenge the validity of the asserted claims. Allowing
BSC to repackage previously-excluded invalidity defenses
in the guise of an ensnarement defense, he argues, is a
“camouflaged or back-handed attack” on the validity of
the asserted claims and effectively an end run around the
right to a jury trial on validity. See Appellant Br. at 47,
50 (quoting Thomas & Betts Corp. v. Litton Sys., Inc., 720
F.2d 1572, 1580 (Fed. Cir. 1983)).
     We are unpersuaded by Dr. Jang’s attempt to conflate
two different concepts. We have explained before that
“[t]he ensnarement inquiry . . . has no bearing on the
validity of the actual claims” asserted in a case. DePuy,
567 F.3d at 1323 (citing Wilson Sporting Goods, 904 F.2d
at 685). And that is because ensnarement concerns
patentability with respect to a hypothetical patent claim
as opposed to the validity of an actual patent claim. See
Wilson Sporting Goods, 904 F.2d at 685 (“Leaving this
burden [of proving that the range of equivalents sought
does not ensnare the prior art] on [the patentee] does not,
of course, in any way undermine the presumed validity of
[its] actual patent claims. In the present situation, [the
patentee’s] claims will remain valid whether or not [it]
22           JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



persuades us that it is entitled to the range of equivalents
sought here.”). Thus, the fact that BSC could not pursue
a validity challenge of the asserted claims in this litiga-
tion does not somehow mandate that it is likewise barred
from challenging a necessarily-broader set of newly-
minted, hypothetical claims.
    Dr. Jang’s reliance on Thomas & Betts is misplaced.
There, we stated that “[w]here [the] validity [of a patent]
in view of the prior art has not been challenged, the
[district] court is less free to limit the application of the
doctrine of equivalents than where invalidity is specifical-
ly urged . . . .” 720 F.2d at 1580. That observation about
the relative application of the doctrine of equivalents in
two different factual scenarios, however, is not a license
for a patentee to obtain a range of equivalents that en-
snares the prior art, even if an alleged infringer does not
challenge the validity of the underlying patent claims.
See Wilson Sporting Goods, 904 F.2d at 684.
     Third, Dr. Jang was not prejudiced by any lack of pre-
trial discovery as to ensnarement. The district court
ruled that Dr. Jang could proceed with a doctrine of
equivalents theory at trial only shortly before it started.
See J.A. at 68–69. It also alerted the parties during this
time frame that it would conduct an ensnarement hearing
if the jury returned a verdict of infringement under the
doctrine of equivalents. Id. at 12207 (post-verdict Minute
Order: “After directing the [c]lerk to enter the jury’s
verdict into the record, the [district court] reminded
counsel for both parties of its prior ruling that in the event
the jury found in favor of [p]laintiff under the doctrine of
equivalents theory, it would proceed with an evidentiary
hearing on the issue of ensnarement.” (emphasis add-
ed)). By then there was little to no time to reopen discov-
ery, let alone a motion by Dr. Jang to do so, which could
have resulted in a waste of the party’s resources and
disrupted the district court’s case management, had the
jury not returned a verdict of infringement under the
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.           23



doctrine of equivalents. In between the jury’s verdict and
the ensnarement hearing, the parties had “three weeks to
develop evidence, expert opinion, and argument . . . [on
the ensnarement] defense.” Appellant Br. at 34. Each
party was presumably on a level playing field when they
arrived at the hearing. If Dr. Jang deemed otherwise, he
could have moved the district court for an enlargement of
time to conduct additional discovery on the defense.
     Fourth and finally, Dr. Jang argues that “Ninth Cir-
cuit law is clear that any defense not listed in the
[p]retrial [o]rder is waived,” and that because ensnare-
ment was not listed in the pretrial order, the defense was
waived. Appellant Br. at 31–32 (citing Pierce Cty. Hotel
Emps. & Rest. Emps. Health Tr. v. Elks Lodge, 827 F.2d
1324, 1329 (9th Cir. 1987); United States v. First Nat’l
Bank of Circle, 652 F.2d 882, 886 (9th Cir. 1981)). But
this puts the cart before the horse. Dr. Jang has not
adequately articulated why proper preservation of en-
snarement required its explicit mention in the pretrial
order. The pretrial order governs trial, see, e.g., Fed. R.
Civ. P. 16(e), but ensnarement is a legal question for the
district court to decide, and the district court here notified
the parties before trial that it would resolve that question,
if necessary, outside of the trial, see J.A. at 12207. We see
no reason why the district court should have mentioned
ensnarement or the contingent post-trial hearing on
ensnarement in the pretrial order under these circum-
stances.
    In sum, the district court permissibly conducted a
post-trial ensnarement hearing after finding that BSC
timely raised the defense, and it appropriately vacated
the jury verdict of infringement under the doctrine of
equivalents and entered judgment of non-infringement for
BSC when Dr. Jang failed to demonstrate through a
proper hypothetical claim analysis that his doctrine of
equivalents theory did not ensnare the prior art.
24           JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.



                     C. Cross-Appeal
    BSC cross-appeals the denial of its motion for sum-
mary judgment, in which the district court held that it
owed royalties to Dr. Jang, if the Express stent were
covered by the asserted claims, notwithstanding the
PTO’s eventual cancellation of those claims. We dismiss
the cross-appeal because it does not seek to enlarge the
district court’s judgment of non-infringement in its favor.
Instead, the cross-appeal merely offers an alternative
basis to affirm the judgment. See Howmedica Osteonics
Corp. v. Wright Med. Tech., Inc., 540 F.3d 1337, 1343 n.2
(Fed. Cir. 2008) (dismissing “cross-appeal as improper
because it did not seek to enlarge the judgment but mere-
ly asserted an alternative ground to affirm the judg-
ment”); see also Symantec Corp. v. Computer Assocs. Int’l,
Inc., 522 F.3d 1279, 1294–95 (Fed. Cir. 2008). When an
improper cross-appeal is dismissed, we may nonetheless
consider the arguments raised as alternative grounds for
sustaining the judgment. Symantec, 522 F.3d at 1294.
Because we affirm the district court’s judgment on other
grounds, we need not do so here.
                       CONCLUSION
     Based on the foregoing analyses, the district court
correctly denied Dr. Jang’s motion for JMOL of literal
infringement of claims 1 and 8 of the ’021 Patent as
substantial evidence supported the jury’s verdict of no
literal infringement. The district court properly vacated
the jury’s finding of infringement under the doctrine of
equivalents because it correctly concluded that Dr. Jang
did not meet his burden of proving that his doctrine of
equivalents theory did not ensnare the prior art as he
failed to draft a proper hypothetical claim. The district
court consequently entered judgment of non-infringement
in favor of BSC, and we affirm that entry of judgment.
We dismiss the cross-appeal and need not reach the
arguments it raised.
JANG v. BOS. SCI. CORP. & SCIMED LIFE SYS., INC.   25



                       AFFIRMED.
                           COSTS
    No costs.
