  United States Court of Appeals
      for the Federal Circuit
                ______________________

      THE OHIO WILLOW WOOD COMPANY,
               Plaintiff-Appellant,

                           v.

                 ALPS SOUTH, LLC,
               Defendant-Cross Appellant.
                ______________________

                 2012-1642, 2013-1024
                ______________________

   Appeals from the United States District Court for the
Southern District of Ohio in No. 04-CV-1223, Judge
Gregory L. Frost.
                  ______________________

              Decided: November 15, 2013
                ______________________

    JEFFREY S. STANDLEY, Standley Law Group, LLP, of
Dublin, Ohio, argued for plaintiff-appellant. With him on
the brief were JAMES L. KWAK, F. MICHAEL SPEED, JR., and
MICHAEL STONEBROOK.

    RONALD A. CHRISTALDI, Shumaker, Loop & Kendrick,
LLP, of Tampa, Florida, argued for defendant-cross
appellant. With him on the brief was MINDI M. RICHTER.
Of counsel on the brief was DAVID W. WICKLUND, of Tole-
do, Ohio.
                 ______________________
2                  OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


     Before DYK, BRYSON, and REYNA, Circuit Judges.
REYNA, Circuit Judge.
    This suit was filed by The Ohio Willow Wood Compa-
ny (“OWW”) against Alps South, LLC (“Alps”) for in-
fringement of United States Patent No. 5,830,237 (the
“’237 patent”). The United States District Court for the
Southern District of Ohio granted summary judgment
that: (1) OWW was collaterally estopped from challenging
the invalidity of claims 1, 2, 4, 15, 16, and 20 of the ’237
patent; (2) claims 18, 19, 21, 22, and 23 of the ’237 patent
were invalid for obviousness; and (3) Alps failed to raise a
genuine issue of material fact with respect to inequitable
conduct. We affirm on the issues of collateral estoppel
and obviousness, but reverse and remand on the issue of
inequitable conduct.
                     I. BACKGROUND
    OWW is the owner of a family of related patents di-
rected to cushioning devices that go over the residual
stumps of amputated limbs to make the use of prosthetics
more comfortable. A variety of these patents have been
asserted in patent infringement suits and many have also
been involved in reexamination proceedings before the
Patent and Trademark Office (“PTO”).
    In the present suit, OWW filed its complaint against
Alps for infringement of the ’237 patent on December 27,
2004. The ’237 patent, entitled “Gel and Cushioning
Devices,” lists Bruce G. Kania as the sole inventor and
has an application date of March 5, 1996. The parties
exchanged contentions, documents, and testimonial
evidence related to invalidity and infringement and on
March 31, 2006, the district court issued its claim con-
struction order. Shortly after receiving the claim con-
struction order, Alps initiated the first of two consecutive
ex parte reexaminations of the ’237 patent in the PTO.
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC                 3


The district court stayed the litigation during these
reexamination proceedings.
      A. The First Reexamination of the ’237 patent
    Alps requested the first ex parte reexamination of the
’237 patent on October 5, 2006. The primary reference
submitted by Alps to support this reexamination was a
prior art gel liner manufactured by Silipos, Inc. (“Silipos”)
called the “Silosheath.” The Silosheath is a sock-shaped
piece of nylon fabric that was turned inside out and
dipped into a mineral oil-based polymeric gel material to
create a coating on the interior of the sheath. The gel
coating acts as a cushion and the mineral oil lubricates
the skin when worn over a residual limb.
    The examiner reviewing Alps’ reexamination request
for the ’237 patent was also responsible for a parallel
reexamination proceeding involving OWW’s U.S. Patent
No. 6,964,688 (the “’688 patent”). The ’688 patent is
entitled “Tube Sock-Shaped Covering” and also lists
Bruce G. Kania as the sole inventor. During reexamina-
tion of the ’688 patent, the examiner issued a rejection of
all challenged claims based on the Silosheath prior art.
This same rejection applied equally against the similar
claims of the ’237 patent.
    The examiner held an interview on July 16, 2007, to
discuss the rejections. At the interview, OWW was repre-
sented by attorneys Mr. Eric M. Gayan and Mr. Jeff
Standley, Mr. Jim Colvin, a representative of OWW, and
Mr. Bruce Kania, the named inventor. To overcome the
rejections, a sample Silosheath was shown to the examin-
er and OWW pointed out that the polymeric gel bled
through the permeable nylon fabric, which resulted in
small amounts of residual gel material on the exterior of
the Silosheath. According to OWW, these small amounts
of gel on the outer surface of the Silosheath created points
4                  OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


of friction between a prosthetic and the Silosheath. The
friction points would be uncomfortable to the user and
cause the nylon fabric to rip or tear prematurely.
    OWW argued that the ’688 and ’237 patents claimed
gel liners that excluded any gel on the exterior surface of
the fabric, thereby distinguishing them from the Si-
losheath. Based on this distinction, the examiner allowed
OWW to overcome the Silosheath prior art by amending
the claims to clarify that the gel coating was only on the
interior of the claimed gel liners and, accordingly, exclud-
ed any liners with fabric that allowed gel to bleed through
to the exterior surface. The PTO issued the first reexam-
ination certificate for the amended ’237 patent claims on
September 2, 2008.
    B. The Second Reexamination of the ’237 patent
    On September 8, 2008, six days after completion of
the first reexamination, Alps initiated a second ex parte
reexamination of the ’237 patent challenging the validity
of the amended claims based on another Silipos product
called the “Single Socket Gel Liner” (“SSGL”). Alps
argued that the SSGL was an invalidating prior art gel
liner that did not have any gel on its exterior surface.
Alps supported this assertion with a prior art advertise-
ment of the SSGL and testimony from Mr. Jean-Paul
Comtesse, who had been affiliated with Silipos and in-
volved in the development and production of both the
Silosheath and SSGL.
    The prior art advertisement was published on Janu-
ary 1, 1995, in a prosthetics trade magazine called O & P
Business News (the “1995 COMFORT ZONE” reference).
The advertisement included a photograph of an actual
device being worn and bearing a graphical label identify-
ing it as a “Silipos, Gel Liner, Made in USA,” and the
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC             5


advertisement further indicated that the device in the
photograph was the “Single Socket Gel Liner”:




The 1995 COMFORT ZONE reference further described
the SSGL as a “[b]elow knee gel liner laminated with tri
block copolymer.”
6                  OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


    In addition to the advertisement, Alps provided the
PTO with testimony from Mr. Comtesse in the form of a
declaration and deposition transcript. The deposition
occurred in the present litigation prior to the court’s
issuance of the stay. According to Alps, Mr. Comtesse’s
testimony proved that the SSGL did not have the same
gel bleed-through issues as the Silosheath since he testi-
fied that the SSGL was constructed using a proprietary
DuPont fabric called “Coolmax,” which was different from
the nylon material used with the Silosheath.          Mr.
Comtesse testified that the Coolmax material was thicker
and denser than nylon, making it impermeable so that gel
did not bleed-through to the outer surface of the SSGL.
Thus, Alps asserted that Mr. Comtesse’s testimony,
coupled with the disclosure of the SSGL advertisement,
demonstrated that the amended claims from the first
reexamination were invalid because the prior art SSGL
had no gel on the exterior surface.
    The examiner agreed with Alps and, ultimately, is-
sued a final rejection that all claims of the ’237 patent
were obvious in view of the SSGL and other undisputed
prior art.     The examiner concluded that the 1995
COMFORT ZONE reference substantially disclosed the
limitations of independent claim 1 of the ’237 patent, but
conceded that the advertisement was not conclusive
regarding whether the SSGL had gel only on the interior
of the liner. To address this shortcoming of the reference,
the examiner accepted the Comtesse declaration and
deposition testimony as proof that the SSGL was manu-
factured using the proprietary DuPont Coolmax material
as a fabric. The examiner also accepted Comtesse’s
testimony that the Coolmax material was thicker and less
permeable than the nylon fabric of the Silosheath and,
accordingly, that the SSGL would not allow the gel to
bleed-through to the exterior surface.
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC                 7


    Faced with the examiner’s final rejection of the claims
in view of the SSGL, OWW appealed to the Board of
Patent Appeals and Interferences (“BPAI”).           OWW’s
arguments on appeal to the BPAI were entirely legal in
nature. OWW asserted that the examiner’s rejection was
improper because it relied on the uncorroborated testimo-
ny of Mr. Comtesse, whom OWW characterized as a
highly interested party. According to OWW, the uncor-
roborated testimony of a highly interested witness, such
as Mr. Comtesse, was inadmissible and therefore could
not be used to reject the claims. In its brief to the BPAI,
OWW portrayed Mr. Comtesse as follows:
   Mr. Comtesse admits that he is an interested par-
   ty with respect to the outcome of this Reexamina-
   tion and the related litigation.        First, Mr.
   Comtesse is the owner and manager of Vorum Re-
   search Corporation . . . a company that appears to
   sell products that compete with products offered
   by Patent Owner. Further, Mr. Comtesse has
   admitted that he continues to receive royalties on
   the Socket Gel Liner products he helped develop
   for Silipos. These Socket Gel Liner products
   would clearly compete with products of Patent
   Owner covered by the ’237 patent. A party having
   a personal financial interest in the outcome of a
   patent suit is considered an interested party. It is
   well settled that issues of corroboration become
   more important and the amount of weight afford-
   ed to such testimony may be lessened when the
   witness is an interested party.
    OWW also expressly denied the existence of any other
evidence that would support Mr. Comtesse’s testimony
that SSGL was constructed using Coolmax fabric. Accord-
ing to OWW, the only evidence of record was the 1995
COMFORT ZONE advertisement, which was “wholly
8                   OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


devoid of any mention of Coolmax.” OWW asserted that
there was “no other evidence of any sort in this regard”
and because “the Comtesse testimony is not corroborated
as required it cannot be properly used to cure the very
deficiencies in the Comfort Zone Ad for which corrobora-
tion is lacking.”
    OWW’s brief to the BPAI was submitted and signed
by Mr. Gayan. During oral argument before the BPAI on
July 20, 2011, Mr. Gayan reiterated OWW’s position that
Mr. Comtesse claimed to be the inventor of the SSGL, that
he was still receiving royalties from Silipos for sales of the
SSGL, and there was no corroborating evidence for his
testimony concerning the construction of the SSGL.
    The BPAI issued its decision regarding OWW’s appeal
on September 30, 2011. The BPAI characterized the
appeal as involving a single dispositive issue: whether the
examiner erred in crediting the uncorroborated testimony
of Mr. Comtesse. The BPAI found that Mr. Comtesse did
not provide any corroborating evidence to support his
assertion that the SSGL depicted in the COMFORT
ZONE-SSGL reference used the Coolmax material. It
also found that Mr. Comtesse “is an interested third party
who is testifying regarding an alleged prior invention said
to have been made by himself and others, namely Silipos’s
Single Socket Gel Liner with Coolmax, to demonstrate the
claims of the ’237 patent are unpatentable.” Based on the
evidence of record, the BPAI concluded that Comtesse’s
testimony was insufficient to sustain the examiner’s
rejection:
    Here, we have not been directed to the requisite
    corroborating evidence.      The statements in
    Comtesse’s Declaration are largely conclusory,
    unaccompanied by credible factual support (e.g.,
    details of experiments or tests performed) and/or
    other acceptable evidence (e.g., testimony of a
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC                9


   credible corroborating witness). . . . Even if the
   Comfort Zone advertisement could be said to cor-
   roborate the Comtesse testimony that a Single
   Socket Gel Liner was made, we have not been di-
   rected to evidence sufficient to corroborate the
   Comtesse testimony indicating that the Liner was
   covered in fabric with no gel bleed-through. For
   these reasons, we conclude that the Examiner
   erred.
Thereafter, a second reexamination certificate for the ’237
patent was issued on November 29, 2011.
              C. The Thermo-Ply Litigation
    While this case was stayed, OWW sued Thermo-Ply,
Inc. (“Thermo-Ply”) in the United States District Court for
the Eastern District of Texas for infringement of United
States Patent No. 7,291,182 (“the ’182 patent”). The ’182
patent issued from a continuation application of the ’237
patent, is entitled “Gel and Cushioning Devices,” and lists
Bruce G. Kania as the sole inventor.
     On summary judgment, the Eastern District of Texas
found the claims of the ’182 patent invalid for obvious-
ness. Ohio Willow Wood Co. v. Thermo-Ply, Inc., No. 9:07-
CV-274, 2009 WL 6499349, at *1 (E.D. Tex. Nov. 20,
2009). The Thermo-Ply court based its obviousness de-
termination on the combination of the Silosheath in view
of U.S. Patent No. 4,923,474 (“the Klasson patent”) and
known techniques in the relevant field. The Thermo-Ply
court rejected OWW’s argument that gel bleeding through
to the exterior surface of the Silosheath fabric rendered
the ’182 patent non-obvious because it would have been
obvious to one of ordinary skill in the art to select an
impermeable fabric. The obviousness determination was
affirmed on appeal. Ohio Willow Wood Co. v. Thermo-Ply,
Inc., 440 F. App’x 926 (Fed. Cir. 2011).
10                  OHIO WILLOW WOOD CO.    v. ALPS SOUTH, LLC


               D. District Court Proceedings
    The district court stayed the litigation from November
22, 2006, to November 3, 2011, pending completion of the
reexaminations proceedings. After the stay was lifted, the
parties filed motions for summary judgment. The district
court granted summary judgment to Alps on issues of
invalidity, finding claims 1, 2, 4, 15, 16, and 20 of the ’237
patent invalid due to the collateral estoppel effect of the
Thermo-Ply litigation and claims 18, 19, 21, 22, and 23 of
the ’237 patent invalid for obviousness. The district court
also granted OWW’s motion for summary judgment of no
inequitable conduct.
    The parties appeal these summary judgment deter-
minations.    We have jurisdiction under 28 U.S.C.
§ 1295(a)(1).
                       II. DISCUSSION
    We review a trial court’s application of collateral es-
toppel, also known as issue preclusion, de novo. Shell
Petroleum, Inc. v. United States, 319 F.3d 1334, 1338
(Fed. Cir. 2003). Likewise, we review a district court’s
grant of summary judgment de novo, drawing all reason-
able inferences in favor of the non-moving party. Teleflex,
Inc. v. Ficosa N. Am. Corp., 299 F.3d 1313, 1323 (Fed. Cir.
2002).
                   A. Collateral Estoppel
    Collateral estoppel protects a party from having to lit-
igate issues that have been fully and fairly tried in a
previous action and adversely resolved against a party-
opponent. Pharmacia & Upjohn Co. v. Mylan Pharm.,
Inc., 170 F.3d 1373, 1379 (Fed. Cir. 1999). Our review of
a collateral estoppel determination is generally guided by
regional circuit precedent, but we apply our own prece-
dent to those aspects of such a determination that involve
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC                11


substantive issues of patent law. Aspex Eyewear, Inc. v.
Zenni Optical Inc., 713 F.3d 1377, 1380 (Fed. Cir. 2013);
see also Aspex Eyewear, Inc. v. Marchon Eyewear, Inc.,
672 F.3d 1335, 1341 n.1 (Fed. Cir. 2012) (“[T]he question
whether a particular claim in a patent case is the same as
or separate from another claim has special application to
patent cases, and we therefore apply our own law to that
issue.”).
     OWW seeks reversal on appeal by arguing that the
mere existence of different language in the adjudicated
claims of the ’182 patent and unadjudicated claims of the
’237 patent is sufficient to overcome collateral estoppel.
We disagree. Our precedent does not limit collateral
estoppel to patent claims that are identical. Rather, it is
the identity of the issues that were litigated that deter-
mines whether collateral estoppel should apply. See
Bourns, Inc. v. U.S., 537 F.2d 486, 491 (Ct. Cl. 1976);
Westwood Chem., Inc. v. U.S., 525 F.2d 1367, 1372 (Ct. Cl.
1975). If the differences between the unadjudicated
patent claims and adjudicated patent claims do not mate-
rially alter the question of invalidity, collateral estoppel
applies. Bourns, 537 F.2d at 493.
    It is without dispute that the asserted claims of the
’237 patent are substantially similar to the invalidated
claims of the ’182 patent:
    The twice-reexamined independent claim 1 of the ’237
patent claims:
   1. A tube sock-shaped covering for enclosing an
   amputation stump, said amputation stump being
   a residual limb, said covering having an open end
   for introduction of said residual limb and a closed
   end opposite said open end, said covering compris-
   ing fabric in the shape of a tube sock, said fabric
   having a coating of a foamed or non-foamed block
12                  OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


     copolymer and mineral oil gel composition resid-
     ing on only an interior surface thereof.
     Independent claim 1 of the ’182 patent recites:
     1. A cushion liner for enclosing an amputation
     stump, said liner comprising a fabric covering
     having an open end for introduction of said stump
     and a closed end opposite said open end, said fab-
     ric coated seamlessly on only an inside surface
     thereof with a polymeric cushioning gel that sub-
     stantially conforms to the shape of said amputa-
     tion stump when said liner is worn; wherein said
     liner is configured such that said polymeric cush-
     ioning gel is in contact with the skin of said ampu-
     tation stump when said liner is worn by a user
     thereof.
     As reflected in the claim language above, these pa-
tents use slightly different language to describe substan-
tially the same invention. For example, where the ’237
patent recites a “tube sock-shaped covering,” an “amputa-
tion stump being a residual limb,” and “fabric in the
shape of a tube sock,” the ’182 patent analogously recites
the same claim scope in the form of a “cushion liner for
enclosing an amputation stump, said liner comprising a
fabric covering having an open end for introduction of said
stump and a closed end opposite said open end.” Thus,
the mere use of different words in these portions of the
claims does not create a new issue of invalidity.
    Nor has OWW explained how any other alleged differ-
ences in claim scope alter the invalidity determination. It
is undisputed that the adjudicated claims of the ’182
patent only require a “polymeric” gel whereas the unadju-
dicated claims of the ’237 patent specifically require a
“block copolymer” gel. OWW argues that this difference
in claim scope precludes summary judgment. But OWW
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC                13


has not adequately supported this contention because it
has not provided any explanation regarding how the
“block copolymer” limitation is patentably significant in
view of the obviousness determination regarding the
claims of the ’182 patent. Since OWW failed to explain
how the “block copolymer” limitation changes the invalidi-
ty analysis, OWW has not met its burden of opposing
summary judgment based on this distinction. Thus,
summary judgment that claims 1, 2, 4, 15, 16, and 20 of
the ’237 patent are invalid on the basis of collateral
estoppel was appropriate.
                     B. Obviousness
    OWW also appeals the district court’s grant of sum-
mary judgment of obviousness of dependent claims 18, 19,
21, 22, and 23 of the ’237 patent. These dependent claims
place numerical limits on certain characteristics of the
“gel composition” and “fabric” of independent claim 1 of
the ’237 patent. Claim 18 and 23 limit the “gel composi-
tion” to those that have “60-85% by weight mineral oil” or
“a Shore A Durometer of from [sic] 1-20,” respectively.
Claims 19, 21, and 22 each require a “fabric” having “an
elasticity of 10-400%.”
    A claim is not patentable “if the differences between
the subject matter sought to be patented and the prior art
are such that the subject matter as a whole would have
been obvious at the time the invention was made to a
person having ordinary skill in the art.” 35 U.S.C. § 103.
Obviousness is a question of law based on underlying
facts. KSR Int’l Co. v. Teleflex, Inc., 550 U.S. 398 (2007).
An assessment of patent invalidity under § 103 involves
the following factors: (1) determining the scope and con-
tent of the prior art; (2) identifying the differences be-
tween the prior art and the claims at issue; (3)
determining the level of ordinary skill in the art; and (4)
reviewing the objective indicia of non-obviousness. See
14                 OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


Graham v. John Deere Co. of Kansas City, 383 U.S. 1, 17-
18 (1966). To support a finding of obviousness on sum-
mary judgment, the court must conclude that one of
ordinary skill in the pertinent art would have found it
obvious to bridge the differences between the subject
matter of the claims and the prior art when the facts are
viewed in a light most favorable to the patentee. See Fed.
R. Civ. P. 54.
    OWW seeks reversal by arguing that the district court
did not perform an adequate obviousness analysis to
support summary judgment. OWW alleges that the
district court used an improper “piecemeal” approach that
was unduly focused on the mere presence of the depend-
ent limitations within the prior art while failing to ana-
lyze the combination of dependent and independent claim
limitations in their entirety. OWW’s argument hinges on
its assertion that the district court provided “no reason-
ing” as to why one of ordinary skill in the art would have
combined the identified references to obtain the claims of
the invention.
    While it is true that “[t]he determination of obvious-
ness is made with respect to the subject matter as a
whole, not separate pieces of the claim,” Sanofi-
Synthelabo v. Apotex, Inc., 550 F.3d 1075, 1085 (Fed. Cir.
2008), nothing in the record indicates that confining the
otherwise obvious “gel composition” and “fabric” limita-
tions to the recited numerical limits in the disputed
dependent claims was anything other than the exercise of
routine skill. Each of these features were well-known in
the prior art and their use would have been predictable by
one of ordinary skill in the art. See Western Union Co. v.
MoneyGram Payment Sys., Inc., 626 F.3d 1361, 1369-71
(Fed. Cir. 2010) (“the common sense of those skilled in the
art demonstrates why some combinations would have
been obvious”).
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC              15


    The record also indicates the existence of devices em-
bodying the features that OWW argues were lacking in
the prior art. The Thermo-Ply court found independent
claim 1 of OWW’s ’182 patent invalid for obviousness
based on the combination of the Silipos Silosheath and
the Klasson patent, the latter of which was commercially
embodied in the ICEROSS liner. The district court con-
cluded that Silipos also had created prior art Gel Liners,
which embodied “gel compositions” with mineral oil
between 60-85% and a Shore A durometer range of 1-20
using a stretchable Coolmax “fabric” having an elasticity
of 10-400%. The SSGL therefore demonstrates the moti-
vation to combine the features of the Silosheath and
Klasson/ICEROSS to meet each of the dependent claim
limitations. Thus, we find there is no genuine issue of
material fact that one of ordinary skill in the art would
have combined the references in a manner that render the
claims obvious.
    We have also considered the evidence presented by
OWW regarding the secondary indicia of non-obviousness.
OWW argues that its commercial liners have been a
success, have satisfied a long-felt but unmet need, have
been copied, and have been praised by the industry, and
this evidence should be enough to demonstrate non-
obviousness. However, these factors equally apply to the
prior art SSGL device and OWW has not shown the
requisite nexus between the secondary indicia and the
patented inventions. See, e.g., In re GPAC Inc., 57 F.3d
1573, 1580 (Fed. Cir. 1995) (“For objective evidence to be
accorded substantial weight, its proponent must establish
a nexus between the evidence and the merits of the
claimed invention.”).    Additionally, where a claimed
invention represents no more than the predictable use of
prior art elements according to established functions, as
here, evidence of secondary indicia are frequently deemed
inadequate to establish non-obviousness. See Western
16                OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


Union Co. v. MoneyGram Payment Sys., Inc., 626 F.3d
1361, 1373 (Fed. Cir. 2010) (“weak secondary considera-
tions generally do not overcome a strong prima facie case
of obviousness”). Thus, OWW’s arguments related to the
secondary indicia do not overcome the conclusion that
dependent claims 18, 19, 21, 22, and 23 of the ’237 patent
are invalid for obviousness.
                 C. Inequitable Conduct
     Inequitable conduct is an equitable defense to patent
infringement. Therasense, Inc. v. Becton, Dickinson and
Co., 649 F.3d 1276, 1285 (Fed. Cir. 2011). It is only
applied where the patentee has unfairly obtained an
unwarranted patent through misconduct. Id. at 1292.
Thus, “[t]o prove inequitable conduct, the challenger must
show by clear and convincing evidence that the patent
applicant (1) misrepresented or omitted information
material to patentability, and (2) did so with specific
intent to mislead or deceive the PTO.” In re Rosuvastatin
Calcium Patent Litig., 703 F.3d 511, 519 (Fed. Cir. 2012)
(citing Therasense, 649 F.3d at 1287).
    Alps argues that there are genuine issues of material
fact regarding OWW’s conduct during the reexamination
proceedings that preclude summary judgment of no
inequitable conduct. Alps’ assertions rely on information
made known to OWW’s counsel in the course of litigation
that was allegedly either withheld or misrepresented in
order to improperly obtain issuance of the ’237 patent
during the reexamination proceedings. 1 Specifically, Alps
alleges that OWW was only able to overcome the examin-

     1  Alps also argues that OWW committed inequita-
ble conduct by intentionally withholding information from
the PTO regarding the Silosheath and Fay liners. We do
not address Alps’ arguments regarding these prior art
devices.
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC               17


er’s final rejection in the second reexamination proceeding
by withholding evidence that corroborated Mr. Comtesse’s
testimony and by falsely exaggerating his interest in the
dispute so that the BPAI would disregard his testimony.
Alps contends that the circumstantial evidence is suffi-
cient to conclude that OWW’s counsel acted with the
specific intent to deceive the PTO.
    OWW responds that there is no evidence to support
an allegation of inequitable conduct. OWW claims that it
did not withhold any information from the PTO and did
not make any intentional misrepresentations material to
the BPAI’s determination that Mr. Comtesse was a highly
interested individual and that his testimony was not
corroborated. Moreover, regardless of any determination
of materiality, OWW contends that there is a lack of clear
and convincing evidence demonstrating that it misrepre-
sented or withheld any information with specific intent to
deceive the PTO.
    We agree with Alps. When viewing the evidence in a
light most favorable to Alps, there are genuine issues of
material fact regarding whether OWW committed inequi-
table conduct during the reexamination proceedings that
preclude summary judgment.
                       1. Materiality
    Typically, an allegation of inequitable conduct before
the PTO requires proof that the patentee withheld or
misrepresented information that, in the absence of the
withholding or misrepresentation, would have prevented
a patent claim from issuing. Therasense, 649 F.3d at
1291. Because the analysis of this but-for materiality
requirement is from the perspective of the PTO, we apply
the preponderance of the evidence standard in assessing
whether the withheld or misrepresented information
would have blocked patentability. Id. at 1291-92.
18                 OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


    A party alleging inequitable conduct, however, need
not strictly demonstrate but-for materiality in all cases.
Rather, “[w]here the patentee has engaged in affirmative
acts of egregious misconduct, such as the filing of an
unmistakably false affidavit,” materiality is presumed.
Id. at 1292 (citations omitted). See also Outside the Box
Innovations, LLC v. Travel Caddy, Inc., 695 F.3d 1285,
1294 (Fed. Cir. 2012) (“a false affidavit or declaration is
per se material”). In this context, materiality is premised
on the notion that “a patentee is unlikely to go to great
lengths to deceive the PTO with a falsehood unless it
believes that falsehood will affect issuance of the patent.”
Id.
    OWW was only able to obtain issuance of the ’237 pa-
tent in the reexamination proceedings by arguing that the
prior art lacked gel liners with no observable gel material
on their exterior surfaces. In the first reexamination
proceeding, OWW expressly amended its claims to distin-
guish them over the prior art Silosheath by emphasizing
this alleged point of novelty over the small amounts of gel
that bled-through the nylon fabric of a sample Silosheath
that OWW brought to an examiner’s interview. In the
second reexamination, OWW was only able to overcome
the examiner’s final rejection in view of the SSGL by
convincing the BPAI that Mr. Comtesse was a highly
interested witness and there was no evidence, as required
by law, to corroborate his testimony that the SSGL was
constructed using a Coolmax fabric. In doing so, contrary
to the district court’s finding below, the BPAI did not
render a substantive conclusion on patentability in view
of the SSGL as prior art. Rather, the BPAI concluded
that the 1995 COMFORT ZONE advertisement was not
by itself sufficient to corroborate Mr. Comtesse’s testimo-
ny regarding the construction of the SSGL. Since there
was no other evidence of record in support of Mr.
Comtesse’s testimony on this subject, the BPAI disregard-
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC                 19


ed the substance of his testimony and reversed the final
rejection for lack of evidentiary support that the SSGL
was constructed using a Coolmax fabric before the March
5, 1995, critical date.
    The crux of our materiality determination therefore
hinges on whether OWW withheld or misrepresented
information that, in the absence of the withholding or
misrepresentation, would have led the BPAI to credit Mr.
Comtesse’s testimony that the pre-critical date SSGL was
constructed using a Coolmax fabric. Although our prece-
dent requires testimony asserted to invalidate a patent to
be corroborated, we do “not impose an impossible stand-
ard of ‘independence’ on corroborative evidence by requir-
ing that every point . . . be corroborated by evidence
having a source totally independent of the witness.”
Lazare Kaplan Int’l, Inc. v. Photoscribe Techs., Inc., 628
F.3d 1359, 1374 (Fed. Cir. 2010) (quoting Knorr v. Pear-
son, 671 F.2d 1368, 1374 (CCPA 1982)). Rather, whether
testimony regarding invalidating prior art is sufficiently
corroborated by documentary, physical, or testimonial
evidence is evaluated under a “rule of reason” standard.
Adenta GmbH v. OrthoArm, Inc., 501 F.3d 1364, 1371
(Fed. Cir. 2007).
    In applying the “rule of reason” test, all pertinent evi-
dence is examined in order to determine whether the
testimony is credible. Sandt Tech., Ltd. v. Resco Metal
and Plastics Corp., 264 F.3d 1344, 1350 (Fed. Cir. 2001)
(quoting Price v. Symsek, 988 F.2d 1187, 1195 (Fed. Cir.
1993)). We have also recognized that:
    Corroborating evidence may take many forms.
    Reliable evidence of corroboration preferably
    comes in the form of records made contemporane-
    ously with the inventive process. Circumstantial
    evidence of an independent nature may also cor-
    roborate. Additionally, oral testimony from some-
20                  OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


     one other than the alleged inventor may corrobo-
     rate.
Linear Tech. Corp. v. Impala Linear Corp., 379 F.3d 1311,
1327 (Fed. Cir. 2004) (internal quotations and citations
omitted); see also Checkpoint Sys., Inc. v. All-Tag Sec.
S.A., 412 F.3d 1331, 1339 (Fed. Cir. 2005) (“Physical,
documentary, or circumstantial evidence, or reliable
testimony from individuals other than the alleged inven-
tor or an interested party, may corroborate.”). As such,
every corroboration case “must be decided on its own facts
with a view to deciding whether the evidence as a whole is
persuasive.” Id. (quoting Cooper v. Goldfarb, 154 F.3d
1321, 1331 (Fed. Cir. 1998)).
   When conducting a rule of reason analysis, this court
generally considers the following eight factors:
     (1) the relationship between the corroborating witness
         and the alleged prior user;
     (2) the time period between the event and trial;
     (3) the interest of the corroborating witness in the
         subject matter in suit;
     (4) contradiction or impeachment of the witness’ tes-
         timony;
     (5) the extent and details of the corroborating testi-
         mony;
     (6) the witness’ familiarity with the subject matter of
         the patented invention and the prior use;
     (7) probability that a prior use could occur considering
         the state of the art at the time; and
     (8) impact of the invention on the industry, and the
         commercial value of its practice.
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC               21


Woodland Trust v. Flowertree Nursery, Inc., 148 F.3d
1368, 1371 (Fed. Cir. 1998).
            a. Withheld material information
    Here, we conclude that a reasonable finder of fact
could conclude that OWW withheld evidence from the
PTO during the second reexamination that sufficiently
corroborated Mr. Comtesse’s testimony regarding the
construction of the SSGL. The corroborating evidence
that OWW did not disclose to the PTO includes witness
testimony, documents, and physical samples.
    In 2006, before the reexamination proceedings, OWW
was provided with three declarations from prosthetists
that were knowledgeable about prosthetic liners that
were available on the March 5, 1995 critical date. Mr.
Robert S. Gailey, Jr., an Associate Professor at the Uni-
versity of Miami School of Medicine, testified that he was
familiar with gel liners from the relevant time period
based on his over 20 years of experience in the field of
prosthetics. Mr. Gailey testified that he was familiar with
Silipos’ products and that their devices “employ[ed] a
variety of fabrics as exterior coverings for the liners and
sleeves.” He further testified that OWW sent him an
SSGL in the mid-1990s, that the covering of the SSGL
was made from a “cotton polyester blend” fabric, that
there is “no bleed-through of the gel,” and that “the fea-
tures of the SSGL remained the same for many years
after its initial introduction.” Mr. Gailey further stated
that he was providing the SSGL he received in the mid-
1990s as an exhibit for the case. 2 While Mr. Gailey stated
that he had consulted for both OWW and Alps in the past,

   2    Alps has submitted evidence demonstrating that
the SSGL was sent to Mr. Gailey on March 28, 1995, and
has also provided photographs of the SSGL, which has a
tag indicating it is constructed with Coolmax material.
22                 OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


he testified that he “ha[s] no stake in the outcome of the
case.” The declarations of the other two prosthetists, Mr.
James McElhiney and Mr. Jack Uellendahl, likewise
asserted that there was no gel on the exterior of the SSGL
because it used a fabric that was thicker and less perme-
able than the nylon fabric of the Silosheath and prevented
gel from bleeding-through to the outside surface. Alt-
hough OWW was aware of the three declarations in
support of Mr. Comtesse’s testimony, it did not disclose
them to the PTO in the reexamination proceedings.
    OWW was also aware that Silipos had filed a patent
application that allegedly covered the commercial embod-
iments of its products (the “Silipos Patent Application”).
There is no evidence that the examiner or the BPAI was
aware of this abandoned patent application. The Silipos
Patent Application was filed on June 15, 1993, and Silipos
provided OWW with a copy of claim amendments and
remarks filed in support of the application on November
29, 1994. That filing covered “protective garments” made
of a fabric outer layer and an inner gel layer worn next to
the skin. Moreover, Silipos’ catalog from the summer of
1995 indicates that there was a “Patent Pending” for the
SSGL, presumably referring to the claims in the patent
application that Silipos disclosed to OWW. This evidence
supports the conclusion that the Silipos Patent Applica-
tion covered the SSGL devices and they only had gel on
their interior surfaces, thereby providing further contem-
poraneous evidence supporting Mr. Comtesse’s testimony
regarding the construction of the SSGL.
    Finally, before the BPAI, Mr. Gayan argued that
there were no known examples of SSGL products from the
relevant time period, and during the review by the panel,
he characterized them as a “ghost.” But SSGL samples
from the relevant period were reviewed by Mr. Comtesse
during deposition. OWW did not provide the actual
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC               23


physical SSGL devices to the PTO or the BPAI, which
would have corroborated Mr. Comtesse’s testimony be-
cause they showed no bleed-through and also corroborate
the fact that the construction of the SSGL remained
unchanged since its initial launch.
    Conversely, OWW does not provide any direct evi-
dence indicating that the SSGL had the same gel bleed-
through issue as the Silosheath. Instead, OWW argues
that none of the documentary or physical evidence before
March 5, 1995, conclusively identifies Coolmax as the
fabric used by the SSGL. 3 OWW’s arguments are mis-
placed. Corroboration does not require that every detail
of the testimony be independently and conclusively sup-
ported by explicit disclosures in the pre-critical date
documents or physical exhibits. See Lazare, 628 F.3d at
1374; Juicy Whip, Inc. v. Orange Bang, Inc., 292 F.3d 728,
741 (Fed. Cir. 2002) (the standard of proof required to
corroborate testimony related to prior public use is not
“beyond a reasonable doubt”) (citing Eibel Process Co. v.
Minnesota & Ontario Paper Co., 261 U.S. 45, 60 (1923)).
Under a “rule of reason” approach, we view the totality of
the evidence pertinent to the testimony, including circum-
stantial evidence, in order to ascertain whether the testi-
monial assertions are credible. See In re Jolley, 308 F.3d
1317, 1325 (Fed. Cir. 2002) (quoting Cooper, 154 F.3d at

   3    OWW also seeks to discredit the cross-
corroborating evidence from the three prosthetists by
arguing that they are interested witnesses whose testi-
mony is not itself corroborated. We disagree. While it
appears that Mr. McElhiney acted as a consultant to Alps,
there is no evidence that Mr. Gailey or Mr. Uellendahl
have any interest in this dispute. Nevertheless, as indi-
cated above, we find that the testimony of these witnesses
is consistent with, and therefore corroborated by, docu-
mentary and physical evidence regarding the SSGL.
24                 OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


1327 (“[c]orroboration may be established by ‘sufficient
circumstantial evidence of an independent nature’”)).
Thus, evidence of corroboration can take many forms and
such evidence does not become irrelevant to the credibility
determination simply because a patentee questions
whether it was created shortly after the critical date. See
Lazare, 628 F.3d at 1375 (undated photograph and video
supplied further evidence to corroborate witness testimo-
ny where it was consistent with documentary evidence
and their accuracy was not challenged by the patentee).
    OWW also argues that Mr. Comtesse testified that the
pre-critical date SSGL was the same product as the
Silosheath. This argument is not supported by the record.
First, OWW relies on truncated excerpts of Mr.
Comtesse’s testimony that are, at best, ambiguous.
However, when viewed against the entirety of Mr.
Comtesse’s testimony and the other evidence available to
OWW, those excerpts are insufficient to support OWW’s
contention that Mr. Comtesse testified that the SSGL and
Silosheath were the same products. Second, the assertion
is directly refuted by other portions of Mr. Comtesse’s
testimony that unequivocally state the Silosheath and
SSGL were separate products, and that the Silosheath
was developed using a nylon fabric and the SSGL devel-
oped with Coolmax fabric. Additionally, OWW’s conten-
tion that the products were the same is also directly
contradicted by the fact that the Silosheath and SSGL
were identified as separate products in Silipos’ pre-critical
date price lists, with distinctly different catalog numbers,
prices, and sizing charts. All of this information indicates
that the Silosheath and SSGL were different products and
OWW’s subjective assertions to the contrary do not ap-
pear to be meritorious.
    Overall, the testimony from the three prosthetists, the
patent application, and the physical exhibits provide
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC               25


consistent and convincing evidence that corroborates Mr.
Comtesse’s testimony regarding the structure of the SSGL
prior to March 5, 1995. It is the cumulative weight of this
evidence that lends credibility to Mr. Comtesse’s testimo-
ny. Accordingly, viewing the evidence in a light most
favorable to Alps, we conclude that there is a genuine
issue of fact regarding whether OWW withheld evidence
from the PTO that was sufficient to corroborate Mr.
Comtesse’s testimony.
         b. Misrepresented material information
    Alps further argues that materiality is demonstrated
by OWW’s misrepresentations to the BPAI in the second
reexamination proceeding. In its brief to the BPAI, OWW
asserted that “Mr. Comtesse admits that he is an inter-
ested party with respect to the outcome of this Reexami-
nation and the related litigation” and that “Mr. Comtesse
has admitted that he continues to receive royalties on the
Socket Gel Liner products he helped develop for Silipos.”
During the hearing before the BPAI, OWW’s counsel, Mr.
Gayan, reiterated these assertions and further asserted
that Mr. Comtesse was the inventor of the SSGL product.
Alps contends that OWW’s statements of admission and
Mr. Comtesse’s inventorship are unfounded and that
OWW made them in order to exaggerate Mr. Comtesse’s
interest in the dispute and undermine the credibility of
his testimony.
    We agree that OWW misrepresented Mr. Comtesse to
the BPAI. Mr. Comtesse never admitted that he was
interested in the outcome of the present dispute nor did
he ever admit that he was receiving royalty payments at
the time of his deposition in 2006. To the contrary, Mr.
Comtesse’s testimony indicated that his relationship with
Silipos ended in 1999 and that he had no personal stake
in the outcome of the dispute between Alps and OWW:
26                    OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


     Q. Mr. Comtesse, as we sit here today, are you –
        do you have any relationship currently with
        Silipos?
     A. Absolutely none.
     Q. When was the last time you had any relation-
        ship with Silipos?
     A. It was the day when we signed the contract to
        sell the company to SSL.
     Q. And that was what year approximately?
     A. It was ’99.
     Q. 1999?
     A. Yeah.
     Q. And do you currently design, manufacture, or
        sell any prosthetic devices?
     A. No.
     Q. Do you have any financial interest in the out-
        come of the lawsuit between ALPS South Cor-
        poration and Ohio Willow Wood?
     A. No.
     Q. Are you involved in any other lawsuits or liti-
        gation with The Ohio Willow Wood or ALPS
        South Corporation?
     A. No.
     Q. Have you ever received any money or promise
        of money from ALPS South Corporation?
     A. No.
     Q. Do you have any business relationship cur-
        rently with ALPS South Corporation?
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC                27


   A. No.
   Q. Will the outcome of this lawsuit have any af-
      fect either way on you?
   A. No.
Mr. Comtesse also testified that he was not receiving
royalty payments from Silipos:
   Q. Are you still getting a royalty from --
   A. No.
   Q. Silipos?
   A. I sold my share and when [I] sold my share in
      ’98, they pay me out.
    The foregoing testimony and other record evidence di-
rectly contradict OWW’s representations to the BPAI of
Mr. Comtesse’s purported admissions. OWW neverthe-
less claims its statements to the BPAI were justified by
other portions of Mr. Comtesse’s testimony. But the
ambiguous testimony OWW identifies does not plausibly
support a conclusion that Mr. Comtesse made admissions
that he was receiving royalty payments and had a stake
in the outcome of the dispute when viewed against the
entirety of the record evidence.
     Nor does the evidence conclusively establish that Mr.
Comtesse was the sole inventor of the SSGL, as OWW
represented to the BPAI. In patent law, the “inventor” is
the person who conceived of the invention. C.R. Bard,
Inc. v. M3 Sys., Inc., 157 F.3d 1340, 1352 (Fed. Cir. 1998);
Sewall v. Walters, 21 F.3d 411, 415 (Fed. Cir. 1994)
(“[d]etermining ‘inventorship’ is nothing more than de-
termining who conceived the subject matter at issue”).
Here, Mr. Comtesse never admitted he was an “inventor”
or that he conceived of the idea for the SSGL. He only
testified that he was involved in the development of
28                 OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


Silipos’ products and had particular skills that were
beneficial to developing and manufacturing the SSGL.
Conversely, OWW was aware that Mr. Robert Gould (not
Mr. Comtesse) was listed as the inventor on Silipos’
patent application that allegedly covered the SSGL de-
vice. Thus, even if Mr. Comtesse had testified to inven-
torship or conception, which he did not, applying the
proper evidentiary standards to OWW’s assertions of Mr.
Comtesse’s sole inventorship required clear and convinc-
ing evidence not only that Mr. Comtesse conceived of the
SSGL but also that Mr. Gould had not conceived of any
aspect of the SSGL. OWW did not possess any such
information, but nevertheless made the self-serving
assertion to the BPAI that Mr. Comtesse was “the inven-
tor” of the SSGL.
    The record also indicates that OWW’s counsel was
aware that Mr. Comtesse’s level of interest was critical to
convincing the BPAI to reverse the examiner’s final
rejection in the second reexamination. OWW asserted
that: “[i]t is well settled that issues of corroboration
become more important and the amount of weight afford-
ed to such testimony may be lessened when the witness is
an interested party,” “Mr. Comtesse’s interest in the
outcome of this proceeding goes to the weight to be given
to his testimony,” and “Mr. Comtesse is an interested
party and, thus, corroborating evidence of the asserted
SSGL construction is even more necessary.”          These
statements demonstrate that OWW’s counsel knew that
the misrepresentations about Mr. Comtesse’s interest and
inventorship would “affect issuance of the patent” by
triggering heightened scrutiny of his testimony. See
Therasense, 649 F.3d at 1292. Accordingly, viewing the
foregoing facts in a light most favorable to Alps, we find
OWW’s misrepresentations to the BPAI tantamount to
the filing of an unmistakably false affidavit. Since we
recognize such misconduct may be sufficient to satisfy the
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC               29


materiality prong of inequitable conduct, id., the identi-
fied misrepresentations further demonstrate the existence
of genuine issues of material fact regarding materiality.
                         2. Intent
    The specific intent to commit inequitable conduct may
be inferred from indirect and circumstantial evidence. Id.
at 1290. But, deceptive intent must be “the single most
reasonable inference drawn from the evidence.” Id. at
1290 (quoting Star Scientific Inc. v. R.J. Reynolds Tobacco
Co., 537 F.3d 1357, 1366 (Fed. Cir. 2008)). The inference
cannot be based on gross negligence and “when there are
multiple reasonable inferences that may be drawn, intent
to deceive cannot be found.” Id. at 1290-91 (citing Scan-
ner Techs. Corp. v. ICOS Vision Sys. Corp., 528 F.3d 1365,
1376 (Fed. Cir. 2008)). Additionally, because the burden
of proof is on the party alleging inequitable conduct, the
patentee need not offer a good faith explanation for its
alleged misconduct unless a threshold level of deceptive
intent has been demonstrated. Id. at 1291.
     The facts, when viewed in a light most favorable to
Alps, preclude summary judgment on the issue of decep-
tive intent. There is no dispute OWW’s counsel knew that
if the BPAI accepted Mr. Comtesse’s account of the prior
art SSGL then the ’237 patent would not have emerged
from the second reexamination proceeding. Thus, OWW’s
counsel in that proceeding, Mr. Gayan, sought to discredit
Mr. Comtesse’s testimony and, as noted in the foregoing
section, did so by making misrepresentations and mis-
leading statements that were directly refuted by credible
evidence that OWW did not otherwise disclose. Under the
circumstances, this evidence creates a genuine issue of
material fact as to whether Mr. Gayan’s conduct before
the PTO was undertaken for the deliberate purpose of
obtaining an otherwise unwarranted patent.
30                 OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC


    Nor do OWW’s subjective assertions of good faith un-
supported by affidavits or declarations from the attorneys
outweigh the evidence of deceptive intent on summary
judgment. If OWW had simply withheld a single piece of
information or made a single misrepresentation, this
would be a different case. However, OWW withheld
various pieces of material information and had no reason-
able explanation for the several misrepresentations it
made to the PTO. In total, the collective weight of this
evidence supports our conclusion that the evidence would
support a finding of intent that is the single most reason-
able inference to be drawn from the evidence at this stage
of the proceedings.
    We have considered OWW’s remaining arguments
and do not find them persuasive. We leave it to the
district court to determine if the inference of deceptive
intent that we hold could be drawn when viewing the
evidence in a light most favorable to Alps remains after
assessing the credibility of OWW’s witnesses. See, e.g.,
Aventis Pharma S.A. v. Hospira, Inc., 675 F.3d 1324,
1334-1337 (Fed. Cir. 2012) (affirming on the issue of
inequitable conduct because patentee’s asserted good faith
belief for withholding material information from the PTO
was contrary to record evidence and the district court
concluded that the patentee’s witness lacked credibility).
                     III. CONCLUSION
    In conclusion, we affirm the district court’s grant of
summary judgment on the issues of collateral estoppel
and obviousness. However, we hold that there are genu-
ine issues of material fact regarding whether OWW’s
counsel committed inequitable conduct during the reex-
aminations of the ’237 patent. We therefore reverse the
district court’s grant of summary judgment on the issue of
inequitable conduct and remand that issue for trial.
OHIO WILLOW WOOD CO.   v. ALPS SOUTH, LLC                 31


     AFFIRMED IN PART, REVERSED IN PART,
             AND REMANDED
                             COSTS
   Each party shall bear its own costs for this appeal.
