  United States Court of Appeals
      for the Federal Circuit
                ______________________

   EXMARK MANUFACTURING COMPANY INC.,
             Plaintiff-Appellee

                           v.

    BRIGGS & STRATTON POWER PRODUCTS
                 GROUP, LLC,
              Defendant-Appellant
             ______________________

                      2016-2197
                ______________________

    Appeal from the United States District Court for the
District of Nebraska in No. 8:10-cv-00187-JFB-TDT, Chief
Judge Joseph F. Bataillon.
                 ______________________

               Decided: January 12, 2018
                ______________________

   J. DEREK VANDENBURGH, Carlson, Caspers, Vanden-
burgh, Lindquist & Schuman, P.A., Minneapolis, MN,
argued for plaintiff-appellee. Also represented by JOSEPH
W. WINKELS, ALEXANDER RINN.

    MATTHEW WOLF, Arnold & Porter Kaye Scholer LLP,
Washington, DC, argued for defendant-appellant. Also
represented by MARC A. COHN.
                ______________________
2       EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


    Before WALLACH, CHEN, and STOLL, Circuit Judges.
STOLL, Circuit Judge.
    Exmark Manufacturing Company filed suit against
Briggs & Stratton Power Products Group, LLC in the
United States District Court for the District of Nebraska,
alleging infringement of, inter alia, claim 1 of U.S. Patent
No. 5,987,863. The district court entered summary judg-
ment that claim 1 was not invalid because the claim
survived multiple reexaminations involving the same
prior art. The district court also denied summary judg-
ment of indefiniteness with respect to claim 1. 1 The case
proceeded to a jury trial, where the jury found that Briggs
willfully infringed Exmark’s patent. The jury awarded
$24,280,330 in compensatory damages, which the district
court doubled as enhanced damages for Briggs’ willful
infringement.
     Briggs appeals several of the district court’s orders,
including the district court’s: (1) summary judgment that
claim 1 is not anticipated or obvious, (2) denial of sum-
mary judgment that claim 1 is indefinite, (3) denial of a
new trial on damages, (4) evidentiary rulings related to
damages, (5) denial of a new trial on willfulness, and
(6) denial of Briggs’ laches defense.
    We conclude the district court erred by basing its
summary judgment of no invalidity solely on the fact that
claim 1 survived multiple reexaminations. Accordingly,
we vacate the district court’s summary judgment of no
invalidity. We remand to the district court for it to make
an independent determination of whether genuine issues
of material fact preclude summary judgment that claim 1


    1   Although the district court’s anticipation, obvi-
ousness, and indefiniteness analyses addressed all dis-
puted claims of the ’863 patent, Briggs’ appeal focuses on
claim 1.
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.       3
GRP., LLC


is not anticipated or obvious in view of the prior art. We
also hold that the district court erred in denying a new
trial on damages because Exmark’s damages expert failed
to provide an adequate explanation as to how she arrived
at a 5% royalty rate for the patented feature relative to
other conventional features of the accused products. We
also conclude that the district court abused its discretion
by limiting the evidence relevant to damages to prior art
that had been commercialized. Likewise, we conclude
that the district court abused its discretion by excluding
from the willfulness trial evidence relating to patent
validity based on its determination that Briggs’ invalidity
defenses were objectively unreasonable. The district
court’s evidentiary ruling does not comport with the
Supreme Court’s recent decision in Halo Electronics, Inc.
v. Pulse Electronics, Inc., 136 S. Ct. 1923 (2016), mandat-
ing that willfulness is to be determined by the jury re-
gardless of whether Briggs’ defenses were objectively
reasonable. Accordingly, we vacate the jury’s finding of
willfulness, vacate the jury’s damages award, vacate the
district court’s enhanced damages award, and remand for
proceedings consistent with this precedent. We also
affirm the district court’s denial of summary judgment
that claim 1 is indefinite, and affirm its denial of Briggs’
laches defense.
                       BACKGROUND
    Briggs and Exmark are competitors in the high-end
commercial lawn mower industry. Exmark filed suit
against Briggs and Schiller Grounds Care, Inc., 2 alleging,
inter alia, infringement of claim 1 of the ’863 patent. The
’863 patent is directed to a lawn mower having improved
flow control baffles. A baffle is a metal structure under
the mower deck that directs air flow and grass clippings
during operation.


   2   Schiller is not a party in the present appeal.
4       EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


     Claim 1 requires a side wall discharge opening and a
“first flow control baffle” having a certain shape. Specifi-
cally, the claim recites that the first baffle comprises “a
first arcuate baffle portion,” “a first elongated and sub-
stantially straight baffle portion,” and “a second arcuate
baffle portion,” with the elongated and substantially
straight baffle portion “angularly disposed . . . in a chord-
like fashion” with respect to the second cutting blade. Id.
at col. 6 ll. 21–39. The parties refer to this as a “curved-
straight-curved” baffle.
    On appeal, Briggs provides an annotated version of
Figure 4 of the ’863 patent depicting the claimed curved-
straight-curved baffle.




Appellant Br. 13.
    Claim 1 recites in relevant part:
        1. A multiblade lawn mower, comprising:
        ....
        said first side wall having a discharge opening
    formed therein;
        ....
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.         5
GRP., LLC


        a first flow control baffle positioned in said
    mower deck which extends downwardly from the
    interior surface of said top wall between said cut-
    ting blades and said front wall;
        said first flow control baffle extending sub-
    stantially continuously from a first location adja-
    cent the interior surface of said second side wall to
    a second location adjacent the interior surface of
    said first side wall and adjacent the forward end
    of said discharge opening;
        said first flow control baffle comprising a first
    arcuate baffle portion, having first and second
    ends, which extends from the interior surface of
    said second side wall partially around said first
    cutting blade, a first elongated and substantially
    straight baffle portion, having first and second
    ends, extending from said second end of said first
    arcuate baffle portion, a second arcuate baffle por-
    tion, having first and second ends, which extends
    from said second end of said first elongated and
    substantially straight baffle portion partially
    around said second cutting blade;
         said first elongated and substantially straight
    baffle portion being angularly disposed with re-
    spect to the said circle defined by the blade tip
    path of said second cutting blade in a chord-like
    fashion so that the cuttings from said first cutting
    blade will be deflected inwardly within the said
    circle defined by the blade tip path of said second
    cutting blade; . . . .
’863 patent col. 5 l. 60–col. 6 l. 50.
    Claim 1 of the ’863 patent was reexamined by the
United States Patent and Trademark Office on three
occasions. Exmark requested the first reexamination,
which was completed prior to the present suit, and the
6       EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


PTO confirmed the patentability of claim 1. The second
and third reexaminations were requested by Defendants
Schiller and Briggs during the pendency of this case
before the district court. The district court stayed pro-
ceedings pending completion of the reexaminations. The
patentability of claim 1 over the same prior art asserted
in the district court was confirmed in both reexamina-
tions.
    Following the reexaminations, the district court lifted
the stay, and Exmark moved for summary judgment that
claim 1 was not invalid as anticipated or obvious. Relying
solely on the fact that claim 1 survived multiple reexami-
nations, the district court concluded that “no reasonable
juror could find that the defendants have met their bur-
den of proving by clear and convincing evidence that the
claims of the patent are invalid.” Exmark Mfg. Co. v.
Briggs & Stratton Power Prods. Grp., LLC, No.
8:10CV187, 2015 WL 12697086, at *11 (D. Neb. July 28,
2015) (“Summary Judgment Order”).
     Briggs also moved for summary judgment that the
claim limitation “elongated and substantially straight”
rendered claim 1 of the ’863 patent indefinite. The dis-
trict court denied Briggs summary judgment, concluding
that the specification informs one skilled in the art with
reasonable certainty as to the claim limitation’s meaning.
Id.
    The district court granted summary judgment of in-
fringement by Briggs’ original mowers. At the same time,
however, the district court found that genuine issues of
material fact precluded summary judgment of infringe-
ment by Briggs’ redesigned mowers. Id. at *12.
     The case proceeded to trial on whether Briggs’ rede-
signed mowers infringed claim 1, whether Briggs willfully
infringed, and damages. The jury found that Briggs
willfully infringed claim 1 of the ’863 patent with respect
to its originally designed mowers but found that its rede-
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.       7
GRP., LLC


signed mowers did not infringe claim 1. The jury awarded
$24,280,330 in damages.
    Following the jury trial, the district court held a
bench trial on Briggs’ motion for a judgment of laches.
The district court denied the motion, concluding that
Briggs had not shown that it was entitled to the equitable
defense of laches. See Exmark Mfg. Co. v. Briggs &
Stratton Power Prods. Grp., LLC, 186 F. Supp. 3d 977,
988 (D. Neb. 2016). The district court also denied Briggs’
post-trial motion for a new trial on damages and willful-
ness. See Exmark Mfg. Co. v. Briggs & Stratton Power
Prods. Grp., LLC, No. 8:10CV187, 2016 WL 2772122, at
*7 (D. Neb. May 11, 2016). The district court granted
Exmark’s motion for enhanced damages based on Briggs’
willful infringement and doubled the jury’s damages
award. See Exmark Mfg. Co. v. Briggs & Stratton Power
Prods. Grp., LLC, No. 8:10CV187, 2016 WL 2772123, at
*6 (D. Neb. May 11, 2016).
   Briggs appeals. We have jurisdiction pursuant to
28 U.S.C. § 1295(a)(1).
                        DISCUSSION
                             I.
                    SUMMARY JUDGMENT
    We begin by addressing the district court’s summary
judgment that claim 1 of the ’863 patent is not invalid.
     We review the district court’s grant of summary
judgment according to the law of the regional circuit.
Phil-Insul Corp. v. Airlite Plastics Co., 854 F.3d 1344,
1353 (Fed. Cir. 2017). The Eighth Circuit reviews a
district court’s grant of summary judgment de novo. Id.
(citing Wilson v. Spain, 209 F.3d 713, 716 (8th Cir. 2000)).
“Summary judgment is appropriate if ‘the movant shows
that there is no genuine dispute as to any material fact
and the movant is entitled to judgment as a matter of
8       EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


law.’” Id. (quoting Fed. R. Civ. P. 56(a)).
                             A.
    Briggs argues that the district court erred by granting
summary judgment that claim 1 is not invalid as antici-
pated or obvious based solely on the fact that claim 1
survived multiple reexaminations involving the same
prior art. We agree.
    The district court’s summary judgment decision was
limited to a single paragraph containing a single basis.
Specifically, the district court held:
        The court first finds that no reasonable jury
    could find on this record that the defendants have
    met their burden of presenting clear and convinc-
    ing evidence that the claims at issue are invalid
    as anticipated or obvious. The ’863 patent has
    now been examined four times by the PTO, and
    each time the PTO held the claims of the ’863 pa-
    tent to be patentable. The court has considered
    the PTO reexaminations and affords them some,
    though not determinative, weight. All of the de-
    fendants’ prior art invalidity arguments have been
    fully considered by the PTO and rejected. The
    PTO has similarly rejected the argument that the
    claims were anticipated by the plaintiffs’ own bro-
    chures and that the patent is not entitled to a pri-
    ority date of 1995. Under these circumstances, the
    court finds that no reasonable juror could find
    that the defendants have met their burden of
    proving by clear and convincing evidence that the
    claims of the patent are invalid.
Summary Judgment Order, 2015 WL 12697086, at *11
(emphases added). Though the district court stated that
it gave the reexaminations “some, though not determina-
tive, weight,” id. (emphasis added), it appears from its
cursory decision that, in fact, the court granted summary
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.       9
GRP., LLC


judgment based on the claim surviving multiple reexami-
nations. No other explanation for granting summary
judgment was provided. The question thus presented is
whether a reexamination confirming patentability of a
claim can form the sole basis for granting summary
judgment that a claim is not invalid based on the same
prior art.
     We hold that a reexamination confirming patentabil-
ity of a patent claim alone is not determinative of whether
a genuine issue of fact precludes summary judgment of no
invalidity. Surviving a reexamination does not warrant
ipso facto summary judgment that a patent is not invalid.
Holding otherwise would improperly give complete defer-
ence and preclusive effect to the PTO’s patentability
determination, foreclosing challenges to patent validity in
district court based on the same prior art.
    Our holding is supported by our prior decisions stat-
ing that a district court “is never bound by an examiner’s
finding in an ex parte patent application proceeding.”
Pfizer, Inc. v. Apotex, Inc., 480 F.3d 1348, 1359 (Fed. Cir.
2007) (citing Fromson v. Advance Offset Plate, Inc.,
755 F.2d 1549, 1555 (Fed. Cir. 1985)). We have said the
same regarding an examiner’s findings during reissue
proceedings. See Fromson, 755 F.2d at 1555 (“The Exam-
iner’s decision, on an original or reissue application, is
never binding on a court.”); Interconnect Planning Corp. v.
Feil, 774 F.2d 1132, 1139 (Fed. Cir. 1985) (“IPC’s view is
incorrect that the PTO’s [reissue] decision must be given
controlling weight . . . .”). While the PTO’s findings
during reexamination are “evidence the court must con-
sider in determining whether the party asserting invalidi-
ty has met its statutory burden by clear and convincing
evidence,” they are not dispositive. Fromson, 755 F.2d at
1555.
   Instead, the “deference [owed] to the decisions of the
USPTO takes the form of the presumption of validity
10      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


under 35 U.S.C. § 282. That is, by statute a patent is
valid upon issuance and included within the presumption
of validity is a presumption of non-obviousness.” Pfizer,
480 F.3d at 1359 (emphases added) (citations omitted).
This presumption also follows a patent claim surviving
reexamination. See Superior Fireplace Co. v. Majestic
Prods. Co., 270 F.3d 1358, 1367 (Fed. Cir. 2001) (“Chal-
lenges to the validity of claims, whether regularly issued,
issued after a reexamination . . . or issued after a reis-
sue . . . must meet the clear and convincing standard of
persuasion. This requirement is based on the presump-
tion of validity.” (emphasis added) (citations omitted)).
    The presumption of validity, however, is just that—a
presumption—which can be overcome by the patent
challenger who meets its high burden of proving the
factual elements of invalidity by clear and convincing
evidence. Id. We recognize the district court must con-
sider reexaminations as evidence “in determining whether
the party asserting invalidity has met its statutory bur-
den by clear and convincing evidence.” Pfizer, 480 F.3d at
1360 (quoting Fromson, 755 F.2d at 1555). But just as an
original examination resulting in patent issuance does not
foreclose an invalidity attack in district court, so too does
a reexamination confirming a claim not preclude a patent
challenger from meeting its burden of proving invalidity.
We thus “affirm the obligation of the district court to
reach an independent conclusion.” Interconnect, 774 F.2d
at 1139.
    Exmark concedes that the PTO’s findings on reexami-
nation are not dispositive, see Appellee Br. 30, but it
nonetheless argues that the district court properly gave
those findings substantial weight and considered other
factors in its summary judgment decision. We disagree
with Exmark’s characterization of the district court’s
decision. The district court’s summary judgment was
based solely on the fact that the patentability of claim 1
was confirmed following multiple reexaminations. The
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.      11
GRP., LLC


district court made no other findings regarding the ele-
ments of anticipation or obviousness to determine wheth-
er a genuine issue of material fact precluded summary
judgment.
     Exmark cites two cases in which this court previously
affirmed summary judgment in view of reexamination
proceedings. But neither case supports the district court’s
analysis in this case. In Transmatic, Inc. v. Gulton Indus-
tries, Inc., we affirmed the district court’s summary
judgment that patent claims were not invalid following
reexamination. 53 F.3d 1270 (Fed. Cir. 1995). But there,
we concluded that “[i]t [was] apparent from the district
court’s opinion that the court considered all the relevant
prior art . . . in reaching its nonobviousness determina-
tion.” Id. at 1275. Only after reaching this conclusion did
we note that “[t]he claims twice passed scrutiny in the
PTO, including a reexamination procedure in which [the
patent challenger] participated as the requester.” Id.
Thus, we do not read Transmatic as condoning a grant of
summary judgment based on the reexamination outcome
alone.
    Similarly, in SRI International, Inc. v. Advanced
Technology Laboratories, Inc., a non-precedential deci-
sion, we affirmed summary judgment of nonobviousness
in view of prior art that had been considered by the PTO
during reexamination. 45 F.3d 443, 1994 WL 712487
(Fed. Cir. 1994) (non-precedential). We stated that “[b]y
issuing the reexamination certificate, the Patent Office
concluded that the asserted claims would not have been
obvious in view of [the prior art reference]” and, accord-
ingly, “‘[d]eference [was] due the Patent Office decision to
issue the patent with respect to evidence bearing on
validity which it considered.’” Id. at *3 (second alteration
in original) (citations omitted). We explained that, “when
a party attacking validity relies only on prior art that was
before the PTO examiner during prosecution, that party
has [the] added burden of overcoming the deference due a
12      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


qualified governmental agency.” Id. (citing Polaroid Corp.
v. Eastman Kodak Co., 789 F.2d 1556, 1560 (Fed. Cir.
1986)). But the district court in SRI did not grant sum-
mary judgment based on the reexamination outcome
alone. Instead, it considered all the record evidence,
including the prior art and expert testimony, to conclude
that the parties’ arguments regarding the prior art did
not create an issue of fact and summary judgment of
invalidity was appropriate. See id. at *3–4.
    Finally, Exmark asserts that Briggs’ strategic deci-
sion to challenge validity through reexamination at the
PTO gave Briggs advantages that it would not get in
district court, including a lack of a presumption of validity
and the ability to rely on the broadest reasonable inter-
pretation. Therefore, Exmark argues, Briggs cannot
ignore the result of reexamination having chosen its
forum and lost. Exmark seems to suggest that because
Briggs was unable to invalidate the claims under a lower
standard of patentability and a broader claim construc-
tion standard, Briggs cannot establish invalidity by clear
and convincing evidence. While this argument seems
facially logical, it fails nonetheless.
     It is important to consider the substantive and proce-
dural differences between challenging patentability in an
ex parte reexamination and challenging patent validity in
federal court. Notably, unlike challenging validity in
district court, in an ex parte reexamination, the claims
are construed under the broadest reasonable interpreta-
tion, the patent challenger does not participate beyond its
initial request for reexamination, the admission of evi-
dence is not governed by the Federal Rules, and the
burden of proving unpatentability is merely a preponder-
ance of evidence. Such differences, however, are material
in district court litigation. For example, the scope of the
construed claims, particularly to the extent there are
differences between the PTO’s and district court’s con-
struction, must be considered in determining whether a
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.         13
GRP., LLC


genuine issue of material fact exists as to whether a prior
art reference anticipates or renders a claim obvious.
    In this case, the district court adopted the parties’
agreed-to construction of “first flow control baffle” as “a
front structure within the walls of the mower deck that
controls the flow of air and grass clippings.” Exmark Mfg.
Co. v. Briggs & Stratton Power Prods. Grp., LLC, No.
8:10CV187, 2011 WL 5976264, at *4 (D. Neb. Nov. 29,
2011); see also J.A. 1558 at 105:14–18. On appeal of the
reexamination before the Board, in which Briggs did not
participate, Exmark and the examiner disagreed about
the proper interpretation of “baffle” and “flow control
baffle.” Exmark argued that “the entire first flow control
baffle must be a baffle, and thus, the individual baffle
portions must also be baffles,” and that “a ‘baffle’ needs to
control the flow of air and grass clippings.” J.A. 3708.
The Board agreed with Exmark and construed “baffle”
and “flow control baffle” as “an element that ‘controls’ the
flow of air and grass clippings within the mower deck in a
‘meaningful way.’” J.A. 3707.
     In its summary judgment decision, however, the dis-
trict court apparently did not agree with all aspects of the
Board’s construction.      The district court stated that
“Exmark’s purported contention that the baffle must have
a ‘meaningful effect’ is not in the claim, but was argued to
the PTO.”       Summary Judgment Order, 2015 WL
12697086, at *10 n.8. The district court then stated:
        The court’s decision does not hinge on the
    “meaningful effect” construction. The “meaningful
    effect” language was adopted by the [Board] mere-
    ly to explain why the mounting plates of the prior
    art . . . patent were not “flow control baffles.” The
    parties previously agreed to the interpretation of
    the claim term “flow control baffle” to mean the
    “structure within the walls of the mower deck that
    controls the flow of air and grass clippings.” That
14       EXMARK MFG. CO.    v. BRIGGS & STRATTON POWER PRODS.
                                                     GRP., LLC


     term is easily understood. The court will not
     adopt the construction that every portion of the
     baffle have a meaningful effect on the flow of air
     and grass clippings.
Id. (citation omitted). 3
    To the extent the district court adopted a broader con-
struction than the PTO’s construction, it precluded Briggs
from arguing that the prior art anticipated the claims or
rendered them obvious under the district court’s broader
construction of the claims. The fact that the Board held
that the asserted anticipating prior art reference did not
disclose the claim requirements (entire baffle and mean-
ingful effect) as construed by the Board, does not foreclose
the possibility that a jury may find otherwise under a
broader construction not requiring those aspects. Thus,
contrary to Exmark’s argument, the mere fact that the
asserted claims survived Briggs’ requested reexamination
does not necessarily establish that it cannot meet its
burden to overcome the presumption of validity under a
broader claim construction.
                               B.
     In the alternative, Exmark argues that we should
affirm the district court because no reasonable juror could
conclude that the prior art anticipates or renders obvious
claim 1 of the ’863 patent. On appeal, the parties ada-
mantly dispute whether the prior art discloses the
claimed “first flow control baffle” and “discharge opening.”
Moreover, the parties appear to present a claim construc-


     3  This statement by the district court appears in a
footnote discussing indefiniteness. On remand, the dis-
trict court should consider how its claim construction, to
the extent it is the same or different from the Board’s
construction, impacts its anticipation and obviousness
analysis.
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.      15
GRP., LLC


tion dispute on appeal: whether the claims of the ’863
patent require that the first flow control baffle be spaced
apart from the front wall.
    It is unclear, however, from the limited record before
us, the extent to which these arguments were raised
before the district court on summary judgment. Indeed,
the district court did not address these arguments. We
are mindful that we review the district court’s judgment,
not its opinion, and review the grant of summary judg-
ment de novo. But we decline the invitation to scour the
record to determine in the first instance whether genuine
issues of fact preclude summary judgment with respect to
the teachings of the prior art, particularly where claim
construction issues were not clearly presented or ad-
dressed by the district court. Cf. OSRAM Sylvania, Inc. v.
Am. Induction Techs., Inc., 701 F.3d 698, 707–08 (Fed.
Cir. 2012) (“It is not our role to scour the record and
search for something to justify a lower court’s conclusions,
particularly at the summary judgment stage. Whether
dealing with an issue of law like claim construction or an
issue of fact such as infringement, this court must be
furnished ‘sufficient findings and reasoning to permit
meaningful appellate scrutiny.’” (citations omitted)).
    Accordingly, we vacate the district court’s summary
judgment of no invalidity and remand with instruction for
the district court to consider the entire record and reach
its own independent conclusion on whether a genuine
issue of fact exists regarding invalidity consistent with
this opinion. The district court should resolve any re-
maining claim construction disputes relevant to the
invalidity analysis. The district court should weigh all
the evidence, including, but not limited to, the evidence
considered by the PTO during reexamination, mindful
that the evidence must be viewed in the light most favor-
able to Briggs, with all justifiable inferences drawn in its
favor. While the reexamination evidence is to be consid-
16       EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                    GRP., LLC


ered, it is not dispositive of the issue on summary judg-
ment.
                              II.
                     INDEFINITENESS
    Briggs also argues that the district court erred in
denying summary judgment that claim 1 of the ’863
patent is indefinite. Briggs contends that the ’863 patent
does not explain how to objectively determine whether a
baffle portion is straight enough or long enough to be
“elongated and substantially straight” for purposes of
determining infringement. We disagree.
    Pursuant to 35 U.S.C. § 112, ¶ 2, a patent specifica-
tion must “conclude with one or more claims particularly
pointing out and distinctly claiming the subject matter
which the applicant regards as his invention.” 4 A claim is
indefinite if, when read in light of the specification and
prosecution history, it fails to inform those skilled in the
art about the scope of the invention with reasonable
certainty.      Nautilus, Inc. v. Biosig Instruments,
Inc., 134 S. Ct. 2120, 2129 (2014). The district court’s
ultimate determination that a patent claim is not indefi-
nite under § 112 is a question of law, which we review de
novo. UltimatePointer, L.L.C. v. Nintendo Co., 816 F.3d
816, 826 (Fed. Cir. 2016).
    We agree with the district court that the claim lan-
guage and specification of the ’863 patent provide reason-
able certainty as to the meaning of “elongated and



     4   Because the ’863 patent was filed before the adop-
tion of the Leahy–Smith America Invents Act, Pub. L. No.
112–29, § 4(e), 125 Stat. 284, 296-97 (2011), the pre-AIA
version of § 112 governs. See AbbVie Deutschland GmbH
& Co., KG v. Janssen Biotech, Inc., 759 F.3d 1285, 1290
n.3 (Fed. Cir. 2014).
EXMARK MFG. CO.    v. BRIGGS & STRATTON POWER PRODS.     17
GRP., LLC


substantially straight.” Claim 1 recites that the elongat-
ed and substantially straight baffle portion “extend[s]
from [the] second end of [the] first arcuate baffle portion”
and that a second arcuate baffle portion “extends from
[the] second end of [the] first elongated and substantially
straight baffle portion.” ’863 patent col. 6 ll. 26–30.
     The specification similarly explains that this elongat-
ed and substantially straight baffle portion is located
between two “arcuate” (curved) baffle portions, both of
which extend partially around a mower blade. Id. at
col. 4 ll. 8–17. Figures 3 and 4 also show that the elon-
gated and relatively straight portion of the baffle extends
such that the elongated portion connects two arcuate
portions of the baffle. Id. Figs. 3 and 4.
    Therefore, the claims and specification provide that
the elongated and straight portion of the baffle must be
long enough and straight enough to at least connect these
two arcuate portions of the baffle. This is illustrated
clearly in Exmark’s annotated depiction of Figure 4 of the
’863 patent below:




Appellee Br. 41.
    The specification also refers to a “relatively straight
baffle portion.” ’863 patent col. 4 ll. 11–12 (emphasis
added). It is clear from the disclosure that the “substan-
18      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


tially straight” portions are straight relative to the curved
baffle portions. This is consistent with Exmark’s experts’
testimony that the “elongated and substantially straight”
terms should be construed as “relative to the proportions
of the other components” and that one of ordinary skill in
the art would understand the limitation to mean “some-
thing which is longer than it is wide, for something which
is relatively straight, for something which transitions
between arcuate portions, something which meets the
chord-like limitation.”       J.A. 11679 at 210:13–17;
J.A. 11127 at 67:14–23.
     Though Briggs seeks to impose a strict requirement of
how straight the baffle portions must be, no such numeri-
cal precision is required when using such terms of degree.
See Sonix Tech. Co. v. Publ’ns Int’l, Ltd., 844 F.3d 1370,
1377 (Fed. Cir. 2017) (“[W]e have rejected the proposition
that claims involving terms of degree are inherently
indefinite. Thus, ‘a patentee need not define his invention
with mathematical precision in order to comply with the
definiteness requirement.’” (quoting Invitrogen Corp. v.
Biocrest Mfg., L.P., 424 F.3d 1374, 1384 (Fed. Cir. 2005)));
see also Apple Inc. v. Samsung Elecs. Co., 786 F.3d 983,
1002 (Fed. Cir. 2015) (upholding a claim term “substan-
tially centered” as definite because the patent challenger
failed to produce evidence that an ordinarily skilled
artisan would lack reasonable certainty of the claim’s
scope), rev’d and remanded on other grounds, 137 S. Ct.
429 (2016); Enzo Biochem, Inc. v. Applera Corp., 599 F.3d
1325, 1335 (Fed. Cir. 2010) (“Because the intrinsic evi-
dence here provides a general guideline and examples
sufficient to enable a person of ordinary skill in the art to
determine [the scope of the claims], the claims are not
indefinite even though the construction of the term ‘not
interfering substantially’ defines the term without refer-
ence to a precise numerical measurement.” (alteration in
original) (citations and internal quotation marks omit-
ted)). All that is required is some standard for measuring
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.      19
GRP., LLC


the term of degree. Biosig, 783 F.3d at 1378. In this case,
one skilled in the art would understand that the “substan-
tially straight” portions of the baffle must be sufficiently
straight to connect two arcuate portions of the baffle.
    The function of the elongated and substantially
straight baffle portions provides further guidance regard-
ing the scope of the claim language. Functional language
can “promote[] definiteness because it helps bound the
scope of the claims by specifying the operations that the
[claimed invention] must undertake.” Cox Commc’ns, Inc.
v. Sprint Commc’n Co. LP, 838 F.3d 1224, 1232 (Fed. Cir.
2016). The claims of the ’863 patent recite that the “elon-
gated and substantially straight baffle portion[s]” are
oriented in such a way “that the cuttings from said first
cutting blade will be deflected inwardly within the said
circle defined by the blade tip path of said second cutting
blade.” ’863 patent col. 6 ll. 36–39. Thus, one skilled in
the art would understand that the elongated and straight
portions of the baffle must be extended, straightened, and
positioned in such a way that the grass cuttings from each
blade deflect the clippings into the direction of the next
blade.
    Briggs cites our recent decision in GE Lighting Solu-
tions, LLC v. Lights of America, Inc., in which we found
the claim term “elongated” indefinite. 663 F. App’x 938
(Fed. Cir. 2016). We note that GE Lighting is a non-
precedential decision, which is not binding, and should be
read as limited to the particular claim and specification at
issue in that case. Further, our indefiniteness determina-
tion in GE Lighting was based on our conclusion that
nothing in the patent at issue provided any objective
boundaries for the term “elongated.” Id. at 940–41. In
contrast, as we explained above, we find that the ’863
patent does provide information to objectively define the
scope of the “elongated” claim term.
20      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


     Briggs also argues that Exmark’s own experts were
unable to explain how a competitor would be able to
determine if their baffles infringe. We are not persuaded
by this argument. Exmark’s expert and co-inventor of the
’863 patent, Garry Busboom, testified that if the length of
the “elongated and substantially straight” baffle portion
were too short, such that it would act as an arcuate baffle
portion, it would not be an elongated and substantially
straight portion. And although Mr. Busboom was unable
to provide any order of magnitude to quantify exactly how
long the elongated baffle portion must be, he testified that
its length was relative to the proportions of other compo-
nents of the baffle and of other mower components. This
testimony is consistent with the claim language and
specification and supports the district court’s conclusion
that one skilled in the art would understand the objective
boundaries of the claim.
    We agree with the district court’s conclusion that
claim 1, when read in light of the specification, informs
those skilled in the art of the scope of the “elongated and
substantially straight” limitation with reasonable certain-
ty. Accordingly, we affirm the district court’s denial of
summary judgment that claim 1 is indefinite.
                             III.
                          DAMAGES
    Briggs also appeals the district court’s denial of a new
trial on damages. For the reasons explained below, we
vacate the jury’s damages award and remand for a new
trial on damages.
    Briggs presents three specific arguments on appeal.
First, Briggs asserts that the district court erred by
permitting Exmark to use the sales price of the accused
mowers as the royalty base instead of the sales price of
the flow control baffles. Briggs next argues that Exmark’s
damages expert’s opinion should have been excluded
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.      21
GRP., LLC


because she failed to adequately explain how she arrived
at her proposed 5% royalty rate. Finally, Briggs asserts
that the district court improperly excluded evidence
relevant to damages. We address each argument in turn.
    “When reviewing damages in patent cases, we apply
regional circuit law to procedural issues and Federal
Circuit law to substantive and procedural issues pertain-
ing to patent law.” Whitserve, LLC v. Comput. Packages,
Inc., 694 F.3d 10, 26 (Fed. Cir. 2012) (quoting Wordtech
Sys., Inc. v. Integrated Networks Sols., Inc., 609 F.3d
1308, 1318 (Fed. Cir. 2010) (internal citations and quota-
tion marks omitted). In the Eighth Circuit, a district
court’s denial of a motion for a new trial on damages is
reviewed for an abuse of discretion. See Harrison v.
Purdy Bros. Trucking Co., 312 F.3d 346, 351 (8th Cir.
2002). Likewise, the district court’s evidentiary rulings,
including those related to the admissibility of damages
expert evidence, are reviewed for an abuse of discretion.
See Barrett v. Rhodia, Inc., 606 F.3d 975, 980 (8th Cir.
2010). “A district court abuses its discretion when its
decision is based on clearly erroneous findings of fact, is
based on erroneous interpretations of the law, or is clearly
unreasonable, arbitrary or fanciful.” Whitserve, 694 F.3d
at 26 (quoting Cybor Corp. v. FAS Techs., Inc., 138 F.3d
1448, 1460 (Fed. Cir. 1998) (en banc)).
                             A.
    Briggs first argues that the district court erred by al-
lowing Exmark to compute a royalty rate without proper-
ly identifying a royalty base to apportion the value of the
patentee’s invention in comparison to the value of the
whole lawn mower. The parties do not dispute that
apportionment is required in this case. Although claim 1
of the ’863 patent is broadly directed to “a multiblade
lawn mower,” our law recognizes that a reasonable royal-
ty award “must be based on the incremental value that
the patented invention adds to the end product.” Erics-
22      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


son, Inc. v. D-Link Sys., Inc., 773 F.3d 1201, 1226 (Fed.
Cir. 2014). Here, the patent makes clear that the patent-
ed improvement relates to the mower’s flow control baffle,
which through its structure and orientation within the
mower deck purportedly efficiently directs grass clippings
toward a side discharge and thereby improves the quality
of grass cut in a manner that distinguishes it from prior
art. See, e.g., ’863 patent col. 1 l. 30–col. 2 l. 9. The
remaining limitations of claim 1 recite conventional
features of a lawn mower, including a mower deck, a side
discharge opening, and a power means for operating the
mower. In these circumstances, the patent owner must
apportion or separate the damages between the patented
improvement and the conventional components of the
multicomponent product.       Cf. Commonwealth Sci. &
Indus. Research Organisation v. Cisco Sys., Inc., 809 F.3d
1295, 1301 (Fed. Cir. 2015) (requiring apportionment
between patented and unpatented features of a multi-
component product); VirnetX, Inc. v. Cisco Sys., Inc.,
767 F.3d 1308, 1329 (Fed. Cir. 2014) (same). This ensures
that Exmark is compensated for the patented improve-
ment (i.e., the improved flow control baffle) rather than
the entire mower. See Garretson v. Clark, 111 U.S. 120,
121 (1884).
    On appeal, Briggs argues that Exmark’s expert should
have apportioned or separated the value of the baffle from
the other features of the mower through the royalty base
rather than the royalty rate. We disagree. We have held
that apportionment can be addressed in a variety of ways,
including “by careful selection of the royalty base to
reflect the value added by the patented feature [or] . . . by
adjustment of the royalty rate so as to discount the value
of a product’s non-patented features; or by a combination
thereof.” Ericsson, 773 F.3d at 1226. So long as Exmark
adequately and reliably apportions between the improved
and conventional features of the accused mower, using the
accused mower as a royalty base and apportioning
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.      23
GRP., LLC


through the royalty rate is an acceptable methodology.
Id. (citing Garretson, 111 U.S. at 121). “The essential
requirement is that the ultimate reasonable royalty
award must be based on the incremental value that the
patented invention adds to the end product.” Id.
    Using the accused lawn mower sales as the royalty
base is particularly appropriate in this case because the
asserted claim is, in fact, directed to the lawn mower as a
whole. The preamble of claim 1 recites a “multiblade
lawn mower.” ’863 patent col. 5 l. 60. It is not the baffle
that infringes the claim, but rather the entire accused
mower. Thus, claim 1 covers the infringing product as
whole, not a single component of a multi-component
product. There is no unpatented or non-infringing feature
of the product. Nonetheless, “[w]hen a patent covers the
infringing product as a whole, and the claims recite both
conventional elements and unconventional elements, the
court must determine how to account for the relative
value of the patentee’s invention in comparison to the
value of the conventional elements recited in the claim,
standing alone.” AstraZeneca AB v. Apotex Corp., 782
F.3d 1324, 1338 (Fed. Cir. 2015) (citing Ericsson, 773 F.3d
at 1233). We hold that such apportionment can be done
in this case through a thorough and reliable analysis to
apportion the royalty rate. We have recognized that one
possible way to do this is through a proper analysis of the
Georgia-Pacific factors. See id; see also Georgia-Pacific
Corp. v. U.S. Plywood Corp., 318 F. Supp. 1116 (S.D.N.Y.
1970). As we have explained, “the standard Georgia-
Pacific reasonable royalty analysis takes account of the
importance of the inventive contribution in determining
the royalty rate that would have emerged from the hypo-
thetical negotiation.” AstraZeneca, 782 F.3d at 1338.
    Finally, we note that Exmark’s use of the accused
lawn mower sales as the royalty base is consistent with
the realities of a hypothetical negotiation and accurately
reflects the real-world bargaining that occurs, particularly
24      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


in licensing. As we stated in Lucent Technologies, Inc. v.
Gateway, Inc., “[t]he hypothetical negotiation tries, as
best as possible, to recreate the ex ante licensing negotia-
tion scenario and to describe the resulting agreement.”
580 F.3d 1301, 1325 (Fed. Cir. 2009). “[S]ophisticated
parties routinely enter into license agreements that base
the value of the patented inventions as a percentage of
the commercial products’ sales price,” and thus “[t]here is
nothing inherently wrong with using the market value of
the entire product, especially when there is no established
market value for the infringing component or feature, so
long as the multiplier accounts for the proportion of the
base represented by the infringing component or feature.”
Id. at 1339. This is consistent with the settlement
agreement relied on by Exmark’s damages expert, which
the parties agree provided an effective royalty of 3.64% of
the sales of the accused mowers.
                             B.
    While we reject Briggs’ argument directed to the roy-
alty base, we ultimately agree with Briggs that Exmark’s
damages expert’s opinion was inadmissible as it failed to
adequately tie the expert’s proposed reasonable royalty
rate to the facts of this case. We conclude that the district
court abused its discretion in denying Briggs’ motion for a
new trial on damages.
    After a discussion of each of the Georgia-Pacific fac-
tors, including the benefits of the patented technology,
sales and profitability, and the competitive relationship of
the parties, Exmark’s expert concluded with little expla-
nation that Exmark and Briggs would have agreed to a
5% reasonable royalty rate on the sales of the accused
lawn mowers as the value for the improved baffle. No-
where in her report, however, did she tie the relevant
Georgia-Pacific factors to the 5% royalty rate or explain
how she calculated a 5% royalty rate using these factors.
To be admissible, expert testimony opining on a reasona-
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.      25
GRP., LLC


ble royalty must “sufficiently [tie the expert testimony on
damages] to the facts of the case. If the patentee fails to
tie the theory to the facts of the case, the testimony must
be excluded.”      Uniloc USA, Inc. v. Microsoft Corp.,
632 F.3d 1292, 1315 (Fed. Cir. 2011) (quoting Daubert v.
Merrell Dow Pharm., Inc., 509 U.S. 579, 591 (1993))
(alteration in original).
    Exmark’s expert began her analysis by explaining her
understanding of the benefits of the mowers covered by
the ’863 patent. Relying on the testimony of experts and
fact witnesses, she identified a number of advantages
arising from the use of the claimed baffle, including
improved air and grass flow for reduced blowout, in-
creased grass cut quality, minimized grass clumping, and
more uniform discharge, all of which improve the mower’s
function and allows a mower to go faster in heavy grass
areas. She concluded that negotiators would have recog-
nized the importance of these advantages to customers
and operators and the key role they play in Briggs’ sale of
its mowers. She repeated these advantages as relevant to
Georgia-Pacific factors nine (utility and advantage of the
patented technology) and ten (the nature of the patented
invention). But she did not explain how these ad-
vantages, or her analysis of the Georgia-Pacific factors,
led to her proposed 5% royalty rate.
     Under similar circumstances, we have held that a
“superficial recitation of the Georgia-Pacific factors,
followed by conclusory remarks, [cannot] support the
jury’s verdict.” Whitserve, 694 F.3d at 31. When an
expert employs the Georgia-Pacific factors, “reciting each
factor and making a conclusory remark about its impact
on the damages calculation before moving on does no
more than tell the jury what factors a damages analysis
could take into consideration.” Id. When performing a
Georgia-Pacific analysis, damages experts must not only
analyze the applicable factors, but also carefully tie those
factors to the proposed royalty rate. “[W]hile mathemati-
26      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


cal precision is not required, some explanation of both
why and generally to what extent the particular factor[s]
impact[] the royalty calculation is needed.” Id.
    Thus, it was not enough for Exmark’s expert to ex-
plain the advantages of the baffle claimed in the ’863
patent and state that they would have been important in
a hypothetical negotiation. This told the jury nothing
more than that the patented technology was important
and commercially successful. A reasonable royalty analy-
sis requires that “the trial court . . . carefully tie proof of
damages to the claimed invention’s footprint in the mar-
ket place.” ResQNet.com, Inc. v. Lansa, Inc., 594 F.3d
860, 869 (Fed. Cir. 2010). To sufficiently tie the ad-
vantages of the patented baffles to the royalty rate in this
case, Exmark’s expert was required to explain the extent
to which they factored into the value of the lawn mower
and her 5% royalty rate.
     The expert’s analysis under Georgia-Pacific factor
thirteen—the portion of realized profits attributable to
non-patented elements—was also troublesome. Exmark’s
expert acknowledged that other elements of the mowers
affect sales and profits of the mowers, including durabil-
ity, reliability, brand position, dealer support, and war-
ranty. But she failed to conduct any analysis indicating
the degree to which these considerations impact the
market value or profitability of the mower and therefore
impacted her suggested 5% royalty rate.
    Equally problematic, the expert acknowledged that
Briggs and its co-defendant, Schiller, have patents cover-
ing other components of the accused mowers. But she
ignored those components, opining without support that
they do not relate to the quality of cut, which she consid-
ered “paramount” to selling mowers. J.A. 14453. We are
skeptical that other patented components of the mower
bear no relation to the overall value of the accused mow-
ers, which would influence the relative value of the pa-
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.     27
GRP., LLC


tented baffle and thus the royalty rate. Even assuming,
however, that they do not, the expert was required to
support her opinion to that effect with sound economic
reasoning. Merely concluding that other components do
not affect the value of the accused mower amounts to
nothing more than speculation. To cure this deficiency,
the jury could have received evidence itemizing the rela-
tive value of these other components to better guide the
jury’s understanding of the value of the baffle in relation
to the other components of the accused multi-component
mower. Without a more detailed analysis, the jury is
simply left to speculate or adopt the expert’s unsupported
conclusory opinion.
    The remainder of Exmark’s expert’s opinion similarly
recited the remaining Georgia-Pacific factors and either
stated that they did not apply or provided a cursory
explanation of the evidence considered for each factor.
The opinion is devoid of any analysis tying either the
evidence or the specific Georgia-Pacific factors to the
proposed 5% royalty rate.
    Exmark defends its expert’s opinion, arguing that her
royalty rate is reasonable because (1) it is only a small
fraction of Exmark’s profits on its mowers; and (2) she
relied on quantitative market valuation evidence in
forming her opinion. Exmark further states that she
considered evidence such as Briggs’ selling value docu-
ments, detailing the value that Briggs placed on each of
its mower’s components, a litigation settlement agree-
ment involving the ’863 patent resulting in a comparable
effective royalty rate, and the parties’ profit margins
during the damages period. We address Exmark’s argu-
ments in turn.
    First, we cannot agree that using an allegedly low
royalty rate alone supports the admissibility of the ex-
pert’s reasonable royalty opinion. Regardless of how low
28      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


the royalty rate, the expert must still apportion damages
and sufficiently tie the royalty rate to the facts of the case.
    Moreover, we recognize that Exmark’s expert dis-
cussed quantitative market evidence in her opinion. As
explained above, however, we are troubled by the expert’s
analysis because, even assuming she properly considered
this record evidence, she failed to explain how the evi-
dence factored into the proposed royalty rate. She merely
addressed the Georgia-Pacific factors in light of the facts
and then plucked the 5% royalty rate out of nowhere. It is
not enough for an expert to simply assert that a particular
royalty rate is reasonable in light of the evidence without
tying the proposed rate to that evidence.
    Because her proposed royalty rate lacked sufficient
ties to the facts of the case, we hold that the district court
erred by not excluding Exmark’s damages expert’s opinion
and abused its discretion by denying Briggs a new trial on
damages based on inadmissible evidence. Accordingly, we
vacate the damages award and remand for a new trial on
damages.
                              C.
    Briggs next challenges three of the district court’s
evidentiary rulings related to damages.
    Briggs first argues that the district court improperly
excluded evidence of certain prior art, which it argues was
related to the damages analysis. Specifically, Briggs
sought to present evidence of conventional modes of
mowing to rebut Exmark’s argument that the mower
claimed in the ’863 patent was a big advancement over
the prior art. Briggs argues that by showing the jury the
small differences between the invention and prior art
mowers, it would have demonstrated that many of the
benefits Exmark attributed to the baffle were already
present in the prior art. The district court allowed the
introduction of some prior art but excluded any prior art
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.     29
GRP., LLC


that had not been commercialized, holding that “prior art
is relevant to damages only to the extent that the patent
was used in a product.” Exmark Mfg. Co. v. Briggs &
Stratton Power Prods. Grp., LLC, No. 8:10:CV187, 2015
WL 5177759, at *4 (D. Neb. Sept. 4, 2015). The district
court appears to have based its ruling on the language of
Georgia-Pacific factor nine, which considers “old modes or
devices, if any, that had been used for working out similar
results.” Georgia-Pacific, 318 F. Supp. at 1120 (emphasis
added).
    We conclude that the district court abused its discre-
tion by holding that prior art is relevant to damages only
to the extent that the prior art was commercialized.
Neither the district court nor Exmark cited any case to
support the view that Georgia-Pacific factor nine limits
evidence of prior art to commercialized modes or devices.
Nor do we see any principled reason for such a narrow
reading. The fact that some prior art mowers were not
commercialized does not make them immaterial to deter-
mining the extent to which the mower claimed in the ’863
patent provides utility and advantages over the prior art.
Moreover, the district court is not constrained by the
Georgia-Pacific factors, as there are ways of determining
a reasonable royalty other than through the Georgia-
Pacific factors. Thus, the language of Georgia-Pacific
factor nine does not bind the district court and should not
be construed as limiting.
    The district court also limited the damages evidence
to prior art directed to side discharge mowers. The record
demonstrates that commercial lawn mowers come in two
varieties, mulching mowers and side discharge mowers.
Briggs argues that the district court abused its discretion
by excluding prior art directed to mulching mowers. We
disagree. The only asserted claim of the ’863 patent
requires a side-discharge mower. Therefore, it was rea-
sonable and within the district court’s discretion to ex-
clude prior art mowers that were not side-discharge
30      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


mowers, commensurate with the scope of the asserted
claim. Thus, we hold that the district court did not abuse
its discretion in excluding evidence of mulching mowers.
    Briggs also argues the district court abused its discre-
tion by excluding evidence of Exmark’s purportedly de-
layed decision to sue for infringement. Briggs argues that
such delay undermines Exmark’s evidence that it would
never have condoned infringement without a high royalty.
    We agree with the district court that Briggs’ attempt
to introduce evidence of Exmark’s delay in filing suit for
infringement is not relevant to damages, even when
considering Georgia-Pacific factors four (licensing policy)
and fifteen (hypothetical negotiation). As the district
court recognized, “[t]he argument that the delay in bring-
ing suit somehow establishes Exmark’s perception of the
value of its invention is specious. There are many reasons
to forego filing a lawsuit, to imply that Exmark did so
because it did not think the invention had value is specu-
lative.” Exmark, 2015 WL 5177759, at *2. The record
supports that there were other reasons for Exmark’s delay
in filing suit, including scarcity of financial resources to
do so. Thus, we conclude that the district court did not
abuse its discretion in excluding this evidence.
                             IV.
                       WILLFULNESS
    Briggs next argues that the Supreme Court’s recent
decision in Halo warrants a new trial on willfulness and
vacatur of the district court’s enhanced damages award.
The willfulness trial in this case proceeded under the
former standard set forth in In re Seagate Technology,
LLC., 497 F.3d 1360 (Fed. Cir. 2007) (en banc). Before
trial, the district court found that Briggs’ litigation de-
fenses were unreasonable. Based on that finding, the
district court precluded Briggs from presenting any
evidence regarding the validity of claim 1 or how closely
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.       31
GRP., LLC


the prior art tracks claim 1. Briggs argues that it should
have been allowed to present such evidence to mitigate
any finding that it acted with an objectively high risk of
infringement. Briggs further argues that the district
court’s exclusion of this evidence is inconsistent with
Halo, which mandates that the inquiry into the degree of
risk of infringement is for the jury, not the district court,
to decide. We agree with Briggs that the district court
erred to the extent it excluded this evidence without also
determining whether it was relevant to Briggs’ state of
mind at the time of accused infringement. Halo, 136 S. Ct.
at 1933 (“[C]ulpability is generally measured against the
knowledge of the actor at the time of the challenged
conduct.”).

     In Halo, the Supreme Court held that “[t]he subjective
willfulness of a patent infringer, intentional or knowing,
may warrant enhanced damages, without regard to
whether his infringement was objectively reckless.” Id.
Thus, under Halo, the district court no longer determines
as a threshold matter whether the accused infringer’s
defenses are objectively reasonable. Rather, the entire
willfulness determination is to be decided by the jury. In
this case, the sole basis for excluding the prior art from
the willfulness trial was the district court’s determination
that Briggs’ litigation defenses were unreasonable. See
id. (criticizing and abrogating our Seagate test because it
improperly “ma[de] dispositive the ability of the infringer
to muster a reasonable (even though unsuccessful) de-
fense at the infringement trial”).

    To the extent that decision excluded evidence relevant
to Briggs’ state of mind at the time of the accused in-
fringement, however, it does not comport with the stand-
ard articulated in Halo, which mandates that willfulness
is an issue for the jury, not the district court. WBIP, LLC
v. Kohler Co., 829 F.3d 1317, 1341 n.13 (Fed. Cir. 2016)
32      EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.
                                                   GRP., LLC


(“[T]here is a right to a jury trial on the willfulness ques-
tion.”). The district court must reconsider its decision to
exclude evidence of the prior art during the jury trial on
willfulness to determine whether Briggs had developed
any views about the prior art at the time of accused
infringement or whether the evidence only relates to
Briggs’ litigation-inspired defenses. Whether there is a
genuine issue of material fact about when Briggs knew of
its prior art defenses, and thus whether a new jury trial is
required, we leave to the district court to determine in the
first instance. See id. at 1340 (“[A]s the Supreme Court
explained in Halo, timing . . . matter[s]. [A party] cannot
insulate itself from liability for enhanced damages by
creating an (ultimately unsuccessful) invalidity defense
for trial . . . .”). Accordingly, we vacate the jury’s finding
of willful infringement, vacate the district court’s en-
hanced damages award, and remand for the district court
to determine whether a new trial on willfulness is neces-
sary.

                             V.
                          LACHES
     Finally, Briggs argues the district court erred by dis-
missing its laches defense. We disagree. The Supreme
Court recently held in SCA Hygiene Products Aktiebolag
v. First Quality Baby Products, LLC, that laches is no
longer a defense against damages for patent infringement
that occurred within 35 U.S.C. § 286’s six-year statute of
limitations period. 137 S. Ct. 954 (2017). Because
Exmark only seeks damages for the six-year period prior
to filing its complaint against Briggs, we agree with the
district court that Briggs cannot assert laches as a de-
fense.
EXMARK MFG. CO.   v. BRIGGS & STRATTON POWER PRODS.       33
GRP., LLC


                       CONCLUSION
     We have considered the parties’ remaining arguments
and find them unpersuasive. In sum, we hold that the
district court improperly relied on the PTO’s reexamina-
tions of claim 1 of the ’863 patent as the sole basis to
grant summary judgment that claim 1 is not invalid. We
remand with instruction for the district court to reach its
own independent conclusion as to whether a factual
dispute regarding invalidity precludes summary judg-
ment. We also vacate the jury’s damages award and the
district court’s award of enhanced damages, and remand
to the district court for, if necessary, a new trial on will-
fulness and damages consistent with this opinion. We
affirm the district court in all other respects.
  AFFIRMED-IN-PART, VACATED-IN-PART, AND
                REMANDED
                           COSTS
    No costs.
