  United States Court of Appeals
      for the Federal Circuit
                ______________________

    PERFECT SURGICAL TECHNIQUES, INC.,
                Appellant

                           v.

 OLYMPUS AMERICA, INC., OLYMPUS MEDICAL
         SYSTEMS CORPORATION,
                  Appellees
           ______________________

                      2015-2043
                ______________________

    Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. IPR2014-
00233.
                 ______________________

              Decided: November 15, 2016
                ______________________

    ROBERT E. FREITAS, Freitas Angell & Weinberg LLP,
Redwood City, CA, argued for appellant. Also represented
by DANIEL J. WEINBERG, JOSHUA YOUNG.

   DEBORAH E. FISHMAN, Kaye Scholer LLP, Palo Alto,
CA, argued for appellees. Also represented by KATIE
JEANNINE LEWIS SCOTT, MARISA ARMANINO WILLIAMS.
               ______________________

 Before MOORE, SCHALL, and O’MALLEY, Circuit Judges.
2    PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



    Opinion for the court filed by Circuit Judge MOORE.
Opinion concurring in part and dissenting in part filed by
                 Circuit Judge SCHALL.
MOORE, Circuit Judge.
     Perfect Surgical Techniques, Inc. (“PST”) appeals
from a decision of the Patent Trial and Appeal Board
(“Board”) invalidating claims 1, 4–6, 8, 9, 11, 12, 38, 41–
44, 46, 47, and 49 of U.S. Patent No. 6,030,384
(“’384 patent”). For the reasons set forth below, we vacate
and remand.
                      BACKGROUND
    This appeal arises from the Board’s inter partes re-
view (“IPR”) decision determining, inter alia, that each of
the claims at issue are anticipated or would have been
obvious over Japanese Application Publication No. H10-
33551 A (“JP ’551”). The Board determined that JP ’551
qualified as prior art to the ’384 patent under 35 U.S.C.
§ 102(a). First, the Board rejected PST’s argument that
the Board could not rely on JP ’551 as filed because the
petitioners, Olympus America, Inc. and Olympus Medical
Systems Corp. (collectively, “Olympus”), failed to trans-
late the bibliographic page containing the publication
date. Second, the Board determined that PST failed to
antedate JP ’551 because it had not proven that the
inventor of the ’384 patent was reasonably diligent in
reducing his invention to practice. After concluding that
JP ’551 was prior art, the Board examined the prior art
under its claim construction and determined JP ’551
anticipated or rendered obvious the claims at issue.
    PST’s appeal addresses all three aspects of the
Board’s decision. We have jurisdiction under 28 U.S.C.
§ 1295(a)(4)(A).
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.    3



                       DISCUSSION
            A. Partial Translation of JP ’551
    Pursuant to 37 C.F.R. § 42.63(b), the Board requires a
party relying on a non-English document to submit “a
translation of the document into English and an affidavit
attesting to the accuracy of the translation.” PST argues
that Olympus’ failure to translate the bibliographic page
of JP ’551 rendered their submission defective and that
the Board violated its own regulations by relying on
Olympus’ partially-translated submission. PST argues
that the bibliographic page contained the publication
date, and since that page was not translated, Olympus did
not present sufficient evidence for the Board to determine
that JP ’551 was prior art to the ’384 patent.
    The Board is not free to disregard its own regulations.
Nor can it mandate compliance by only some parties. But
in this case, even if the Board erred by accepting Olym-
pus’ submission of JP ’551, its error is harmless.
    PST concedes that the only relevant information on
the untranslated page is the publication date, and the
date is discernable from the face of the untranslated page.
See J.A. 13 (citing Manual of Patent Examining Procedure
§ 901.05(a) (describing how to convert Japanese format
publication date information to Gregorian calendar date
information)). As noted by the Board, the translator’s
certification further attested that JP ’551 was published
on February 10, 1998. J.A. 12–13. PST does not dispute
that JP ’551 was published on this date, nor does it dis-
pute the remainder of the translation. For these reasons,
PST has not established that the Board’s acceptance of a
not fully translated version of JP ’551 was anything other
than harmless error.
4       PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



                   B. Antedating JP ’551
                       1. Background
    Pre-AIA section 102(g) allows a patent owner to ante-
date a reference by proving earlier conception and rea-
sonable diligence in reducing to practice. 1 Monsanto Co.
v. Mycogen Plant Sci., Inc., 261 F.3d 1356, 1362 (Fed. Cir.
2001). Reasonable diligence must be shown throughout
the entire critical period, which begins just prior to the
competing reference’s effective date and ends on the date
of the invention’s reduction to practice. Id. at 1363.
     Dr. Camran Nezhat, the inventor of the ’384 patent,
hired James Heslin to draft and file the application that
would issue as the ’384 patent. On January 28, 1998,
Mr. Heslin sent an initial draft of the application to
Dr. Nezhat. Mr. Heslin later filed the application with
the Patent and Trademark Office (“PTO”) on May 1, 1998.
During this 93-day lapse of time—and only thirteen days
after Dr. Nezhat received the initial draft application—
JP ’551 published. To show diligence in reduction to
practice, PST must prove that Dr. Nezhat was reasonably
diligent during the critical period, which began on Febru-
ary 9, 1998, one day prior to JP ’551’s publication date,
and ended on May 1, 1998, the date the invention was
constructively reduced to practice by filing the application
that resulted in the ’384 patent with the PTO.
    Dr. Nezhat testified that he was reasonably diligent
in reducing his invention to practice from February 9 to
May 1, 1998. He testified that, although he did not recall
all of his daily activities, he “diligently worked with


    1   Because the Board determined that PST had not
proven reasonable diligence, it did not reach the issue of
conception. We decline to consider PST’s evidence of
conception for the first time on appeal and therefore limit
our opinion to the issue of reasonable diligence.
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.   5



Mr. Heslin between February 1, 1998 and May 1, 1998,
within the reasonable limits of my busy medical practice
and teaching schedule[.]” J.A. 686. He testified that
throughout these months, his medical practice required
him to work roughly 80 hours per week, during which he
would perform approximately four to six surgeries. Id.
He testified that he submitted comments on the initial
draft application on March 2, received questions from
Mr. Heslin on or around March 4 and 12, participated in a
conference with Mr. Heslin on March 16, and received a
second draft application from Mr. Heslin on April 13.
J.A. 686–87. He testified that he “again carefully re-
viewed the second draft” before it was finalized and filed
on May 1. J.A. 687.
    An inventor’s testimony regarding his reasonable dili-
gence must be corroborated by evidence. Brown v. Bar-
bacid, 436 F.3d 1376, 1380 (Fed. Cir. 2006). A “variety of
activities” may corroborate an inventor’s testimony of
reasonable diligence and such corroborating evidence is
considered “as a whole” under a rule of reason. Id. To
corroborate Dr. Nezhat’s testimony, PST introduced a
declaration from Mr. Heslin, letters between Dr. Nezhat
and Mr. Heslin, and Mr. Heslin’s billing records.
     Mr. Heslin recounted the same dates of activity as
Dr. Nezhat and added that he reviewed and revised the
initial draft application on April 7. J.A. 757–58. He
characterized Dr. Nezhat as a “careful and serious client”
who “communicated with me, in writing and in person, to
finalize the application.” J.A. 758. He testified that he
and Dr. Nezhat “put in a significant amount of effort and
work into revising and finalizing the patent application
between February 1 and May 1.” J.A. 758–59. He testi-
fied that during the relevant time period, he “maintained
a very active practice” and typically worked 50 hours or
more a week. J.A. 756, 758.
   Mr. Heslin’s declaration appended a number of exhib-
6    PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.



its as support for his testimony. A March 12 letter from
Mr. Heslin thanked Dr. Nezhat for his “facsimile of
March 2, 1998, with comments on the initial draft.”
J.A. 927. The letter asked for Dr. Nezhat’s “further
comments on electrode surface area” and requested that
they meet “to discuss finalizing the draft.”            Id.
Mr. Heslin’s billing records indicate he reviewed
Dr. Nezhat’s comments on March 4 and that he met with
Dr. Nezhat on March 16. J.A. 604. The billing records
also indicate Mr. Heslin revised the draft application on
April 7. Id. An April 13 letter from Mr. Heslin to
Dr. Nezhat enclosed a second draft application and ex-
pressed that he “tried to reflect the comments you made
when we last met.” J.A. 607. The letter asked for
Dr. Nezhat’s “further comments so that [the application]
can be finalized and filed in the near future.” Id.
Mr. Heslin filed the application on May 1. J.A. 604, 634.
     The Board accepted Dr. Nezhat’s testimony and cor-
roborating evidence but determined that PST was not
“sufficiently specific as to facts and dates” of Dr. Nezhat’s
diligence during three portions of the critical period:
(1) February 10 to March 1; (2) March 12 to March 15;
and (3) April 13 to May 1. J.A. 21–22. The Board there-
fore concluded that PST failed to demonstrate
Dr. Nezhat’s “continuous exercise of reasonable diligence
for the entire critical period.” J.A. 22.
                      2. Discussion
    Whether a patent antedates a reference is a question
of law based on subsidiary findings of fact. In re Steed,
802 F.3d 1311, 1316–17 (Fed. Cir. 2015). The issue of
reasonable diligence “turns on the factual record, and we
review Board determinations as to diligence for support
by substantial evidence in the record.” Id. at 1317.
Throughout its opinion, the Board repeatedly character-
ized PST’s burden as requiring proof of Dr. Nezhat’s
“continuous exercise of reasonable diligence.” J.A. 16
PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.     7



(emphasis added); see also id. (requiring proof of “continu-
ous and corroborated diligence”); J.A. 18 (“Patent Owner
does not provide sufficient evidence to demonstrate . . .
that Dr. Nezhat continuously exercised reasonable dili-
gence during the entire critical period.”); J.A. 19 (“[T]he
evidence, taken as a whole, does not support Patent
Owner’s contention that there was a continuous exercise
of reasonable diligence during the entire critical period.”);
J.A. 22 (“Patent Owner does not provide sufficient evi-
dence to demonstrate Dr. Nezhat’s continuous exercise of
reasonable diligence . . . .”). The standard demanded by
the Board is too exacting and in conflict with our prece-
dent.
     A patent owner need not prove the inventor continu-
ously exercised reasonable diligence throughout the
critical period; it must show there was reasonably contin-
uous diligence. See, e.g., Tyco Healthcare Grp. v. Ethicon
Endo-Surgery, Inc., 774 F.3d 968, 975 (Fed. Cir. 2014);
Monsanto, 261 F.3d at 1370. Under this standard, an
inventor is not required to work on reducing his invention
to practice every day during the critical period. See
Monsanto, 261 F.3d at 1369. And periods of inactivity
within the critical period do not automatically vanquish a
patent owner’s claim of reasonable diligence. For exam-
ple, in Monsanto, we held that substantial evidence
supported the jury’s presumed finding that an inventor
was reasonably diligent where there was no corroborating
evidence of any activity for a series of months. Id.
at 1370. We explained that, notwithstanding the absence
of daily notebook entries and the resulting gaps during
the critical period, “the work involved in the experiments
was continuous in nature” and therefore the reduction to
practice was “reasonably continuous.” Id. In Brown v.
Barbacid, we held that the patent owner’s evidence of
diligence during a 31-day critical period was “sufficient to
show substantially continuing activity” despite the lack of
activity during six single-day gaps. 436 F.3d at 1380–83.
8   PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.



Our holdings in these cases are consistent with the pur-
pose of the diligence inquiry. In determining whether an
invention antedates another, the point of the diligence
analysis is not to scour the patent owner’s corroborating
evidence in search of intervals of time where the patent
owner has failed to substantiate some sort of activity. It
is to assure that, in light of the evidence as a whole, “the
invention was not abandoned or unreasonably delayed.”
Id. at 1379. That an inventor overseeing a study did not
record its progress on a daily, weekly, or even monthly
basis does not mean the inventor necessarily abandoned
his invention or unreasonably delayed it. The same logic
applies to the preparation of a patent application: the
absence of evidence that an inventor and his attorney
revised or discussed the application on a daily basis is
alone insufficient to determine that the invention was
abandoned or unreasonably delayed. One must weigh the
collection of evidence over the entire critical period to
make such a determination.
     Our decision in In re Mulder, 716 F.2d 1542, 1542–46
(Fed. Cir. 1983), does not instruct otherwise. The Board
cites In re Mulder for the proposition that “[e]ven a short
period of unexplained inactivity may be sufficient to
defeat a claim of diligence.” J.A. 16. In In re Mulder, a
competing reference was published just days before the
patent at issue was constructively reduced to practice.
716 F.2d at 1544. The patent owner was tasked with
showing reasonable diligence during a critical period
lasting only two days. Id. at 1545. But the patent owner
did not produce any evidence of diligence during the
critical period. Id. Nor could it point to any activity
during the months between the drafting of the application
and the start of the critical period. Id. Although the
critical period spanned just two days, we declined to
excuse the patent owner’s complete lack of evidence. Id.
In re Mulder does not hold that an inventor’s inactivity
during a portion of the critical period can, without more,
PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.      9



destroy a patent owner’s claim of diligence.
    Here, the Board’s erroneously heightened burden of
proof infected its analysis. First, the Board did not
properly weigh PST’s evidence under a rule of reason. See
Price v. Symsek, 988 F.2d 1187, 1195 (Fed. Cir. 1993)
(explaining that under a rule of reason analysis, “[a]n
evaluation of all pertinent evidence must be made so that
a sound determination of the credibility of the inventor’s
story may be reached”). Rather than evaluating PST’s
evidence as a whole, the Board fixated on the portions of
the critical period where PST did not provide evidence of
Dr. Nezhat’s specific activities to conclude Dr. Nezhat’s
exercise of diligence was not “continuous.” See J.A. 21–
22. In doing so, the Board repeatedly condemned PST for
not being “sufficiently specific as to facts and dates for the
entire critical period during which diligence is required.”
J.A. 21; see also id. (noting a portion of the critical period
where “Dr. Nezhat does not identify any specific activities
undertaken or the dates of those activities”). The Board
similarly dismissed Dr. Nezhat’s testimony that he “per-
formed approximately four to six surgeries per week” and
worked “roughly 80 hours” per week, J.A. 686, criticizing
that Dr. Nezhat was “unable to identify any single
date . . . on which he was scheduled for a surgery or had
another specific conflict that would have prevented him
from working on preparing the application for filing.”
J.A. 20.
    Under a rule of reason analysis, PST was not required
to corroborate every day the application was worked on,
every surgery Dr. Nezhat performed, or specify precisely
what work was done. See In re Jolley, 308 F.3d 1317,
1328 (Fed. Cir. 2002) (“[C]orroboration may be provided
by sufficient independent circumstantial evidence, and
corroboration of every factual issue contested by the
parties is not a requirement of the law.”). Such corrobora-
tion is particularly unnecessary when, as here, the record
indisputably shows that activities must have occurred
10   PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



within the relevant timeframe. For example, Dr. Nezhat
testified that, from the time he received the questions in
Mr. Heslin’s March 12 letter until the two met on
March 16, “most probably we did everything he wanted us
to do to go to be prepared for him” and that he was “sure
we were prepared to go and see him.” J.A. 1316:17–
1317:5. The Board criticized this testimony, finding that
Dr. Nezhat “does not recall when or how he responded to
[Mr. Heslin’s] questions.” J.A. 21. But in this case, such
specificity was unnecessary. The record clearly shows
that Dr. Nezhat and Mr. Heslin met on March 16,
J.A. 604, and Dr. Nezhat provided comments to
Mr. Heslin by at least April 13 when Mr. Heslin sent a
letter with a revised application to Dr. Nezhat saying he
“tried to reflect the comments you made when we last
met.” J.A. 607.       The revised draft added 7 claims,
8 drawings, and expanded the specification. J.A. 607–31.
The parties do not dispute this evidence. With this evi-
dence before it, the Board did not need the specific dates
on which Dr. Nezhat provided comments and the content
of those comments to evaluate Dr. Nezhat’s testimony
under a rule of reason.
    The Board compounded its error by summarily dis-
missing the activities of Dr. Nezhat’s attorney,
Mr. Heslin, after determining that PST’s evidence of
Dr. Nezhat’s activities did not alone establish reasonable
diligence. J.A. 22 (“[W]e also need not reach and, there-
fore, do not address whether Patent Owner provides
sufficient evidence to demonstrate Mr. Heslin’s continu-
ous exercise of reasonable diligence for the entire critical
period.”). This was error. An attorney’s work in prepar-
ing a patent application is evidence of an inventor’s
diligence. See Brown, 436 F.3d at 1380 (citing Bey v.
Kollonitsch, 806 F.2d 1024, 1030 (Fed. Cir. 1986)). By
preparing and filing the application that would issue as
the ’384 patent on behalf of Dr. Nezhat, Mr. Heslin was
acting as Dr. Nezhat’s agent. The Board was required to
PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.    11



weigh Mr. Heslin’s testimony and evidence of activity as
an extension of Dr. Nezhat’s. And it was required to
weigh this evidence by application of a rule of reason over
the course of the entire critical period.
    By failing to consider Mr. Heslin’s activities, the
Board erroneously found that PST failed to show diligence
during periods when Mr. Heslin was working to construc-
tively reduce the invention to practice. Between the
March 16 conference and Dr. Nezhat’s receipt of the
second draft application on April 13, the Board criticized
that “Dr. Nezhat does not identify any specific activities
undertaken or the dates of those activities.” J.A. 21. In
addition to the work that undoubtedly must have oc-
curred in order to result in a new draft application, the
record indicates that during this time, Mr. Heslin at least
reviewed and revised the application on April 7. J.A. 604.
The Board also flagged PST’s lack of evidence for actions
Dr. Nezhat took after receiving the second draft until
Mr. Heslin filed the application with the PTO, J.A. 21, but
during this time, Mr. Heslin prepared the application and
accompanying disclosure statement and filed these docu-
ments on May 1. J.A. 604. And Mr. Heslin testified that
it was his usual practice to dictate the text of the applica-
tion and allow time, around eight days, for word pro-
cessing to transcribe his edits. J.A. 1528 at 33:1–20.
Evidence of this sort, where the record indisputably shows
an attorney was working to constructively reduce an
invention to practice, highlights the importance of consid-
ering an attorney’s prosecuting activities as part of the
inventor’s diligence.
     The Board’s focus on gaps of inactivity also led it to
make fact findings unsupported by substantial evidence.
The most egregious of these concerns the Board’s finding
of inactivity between March 12 and March 15. J.A. 21–22.
The record indicates that on March 12, in response to
comments received on March 2, Mr. Heslin requested that
they “meet to discuss finalizing the draft.” J.A. 927.
12   PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



March 12, 1998 was a Thursday. Mr. Heslin’s billing
records confirm that he met with Dr. Nezhat the following
Monday, March 16. J.A. 604. The Board determined that
the period from Thursday to Sunday constituted a gap of
inactivity, finding in support that “[n]o evidence is pre-
sented as to the nature of th[e] comments” Dr. Nezhat
sent on March 2 and “[n]o evidence is presented as to the
nature of [the March 16] conference.” J.A. 20–21. First,
the Board’s finding that there was “no evidence” regard-
ing the March 2 comments is unsupported by the record.
Mr. Heslin’s March 12 letter explicitly refers to these
comments and explains that Dr. Nezhat’s comments
“correctly note that the inclusion of pins will increase the
available electrode surface area relative to conventional
(pinless) forceps.” J.A. 927. Second, ample evidence
described the “nature” of the March 16 conference.
Mr. Heslin’s March 12 letter requesting a meeting asked
Dr. Nezhat to clarify whether a device disclosed in anoth-
er reference “would provide the same increase in electrode
area as your device.” Id. The two met on March 16,
which was billed to the patent application matter.
J.A. 604. An April 13 letter from Mr. Heslin states, “I
have tried to reflect the comments you made when we last
met,” which included “various alternative electrode em-
bodiments and described their benefits both in terms of
increased electrode area and enhanced current contain-
ment.” J.A. 607. Together, this evidence poses a question
regarding the invention, shows the two met on March 16,
and shows the question was answered when the two last
met. The Board’s finding that this long weekend amount-
ed to a period of inactivity is unreasonable on its face.
     The Board concluded that the three gaps collectively
demonstrated a lack of diligence during the entire critical
period. The Board makes clear that it is “the evidence,
taken as a whole,” which causes them to find a lack of
diligence “during the entire critical period.” J.A. 19. The
Board did not make a fact finding that any one of these
PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.    13



gaps would be sufficient to establish a lack of diligence for
the entire critical period. The dissent agrees that the
Board’s fact findings regarding two of the three gaps are
not supported by substantial evidence. Thus, even under
the dissent’s analysis, this case should be remanded for
the Board to make the fact finding about whether the
evidence presented regarding what it calls Gap 1 would be
sufficient alone to find a lack of diligence. The Board’s
erroneous finding of inactivity between the periods
March 12 to March 15 and April 13 to May 1 requires
remand. It is for the Board to reconsider the whole record
and make a fact finding on diligence in the first instance.
     For these reasons, the Board’s decision that PST
failed to antedate JP ’551 is vacated and remanded for
proceedings consistent with this opinion. On remand, the
question before the Board is whether all of PST’s evi-
dence, considered as a whole and under a rule of reason,
collectively corroborates Dr. Nezhat’s testimony that he
worked reasonably continuously within the confines of his
and Mr. Heslin’s occupations to diligently finalize the
patent application during the 81-day critical period. 2 If
the answer is yes, the Board is to consider PST’s evidence
of earlier conception in the first instance.
                  C. Claim Construction
    In IPR proceedings, the Board gives claims their



    2   This evaluation must include: (1) Mr. Heslin’s tes-
timony of his and Dr. Nezhat’s activities; (2) Mr. Heslin’s
billing records identifying work on March 4, March 16,
April 7, and May 1; (3) Mr. Heslin’s March 12 letter
thanking Dr. Nezhat for his March 2 comments and
requesting guidance; (4) Mr. Heslin’s April 13 letter and
revisions, adding text to the specification, 7 claims, and
8 drawings; and (5) the finalized patent application filed
on May 1.
14   PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



broadest reasonable interpretation consistent with the
specification. In re Cuozzo Speed Techs., LLC, 793 F.3d
1268, 1279 (Fed. Cir. 2015), aff’d, 136 S. Ct. 2131 (2016).
PST argues the Board erred in its construction of the term
“perforated,” which appears in asserted claims 11 and 38:
“wherein at least one of the jaws is perforated to permit
the release of steam during use.” The Board construed
these claims as requiring that “at least one jaw has one or
more perforations or passages formed therethrough, so
that steam generated between the jaw and tissue is
released . . . .” J.A. 10–11 (emphasis added). The Board
reasoned that the specification, which states “the jaws
may be perforated or otherwise provided with passages,”
describes “passages as another form of perforations and
does not distinguish between these terms.” J.A. 9 (quot-
ing ’384 patent at 3:25–27). The Board cited extrinsic
dictionary definitions in support, including that to “perfo-
rate” means to pierce, puncture, or make any hole.
J.A. 10. We review the Board’s claim construction de novo
except for subsidiary fact findings, which we review for
substantial evidence. Cuozzo, 793 F.3d at 1280.
     Determining the plain meaning of a term to a skilled
artisan at a particular time is a fact finding, and as such
we review it for substantial evidence. Teva Pharm. USA,
Inc. v. Sandoz, Inc., 135 S. Ct. 831, 843 (2015). In this
case, the Board concluded that the plain meaning of the
term “perforated” included passages. It referenced extrin-
sic evidence, namely dictionary definitions which support-
ed its determination of the plain meaning. The legal part
of claim construction is the determination of the meaning
of the term in the claim in light of the patent’s intrinsic
record. PST argues the description in the specification
that the device “may be perforated or otherwise provided
with passages” evidences a difference in meaning between
passages and perforations.          PST Br. 47 (quoting
’384 patent at 3:25–27). We agree. The patentee is free to
define or limit a term used in a patent. See Thorner v.
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.   15



Sony Comput. Entm’t Am. LLC, 669 F.3d 1362, 1365–66
(Fed. Cir. 2012). We conclude that the specification’s
separation of the terms perforated and passages with the
disjunctive phrase “or otherwise” makes clear that the
patentee intended that the term “perforated” is not the
same as “passages.” The patentee claimed only jaws that
are “perforated”; this claim does not extend to passages.
In light of the intrinsic record, we conclude that the term
“perforated” is not coextensive with or the same as “pas-
sages.” Thus the Board’s finding that JP ’551 disclosed at
least one “perforated” jaw because JP ‘551 referenced a
passage cannot be supported. We vacate the Board’s
decision invalidating claims 11, 38, 41–44, 46, 47, and 49
over JP ’551 and remand for proceedings consistent with
this construction.
                       CONCLUSION
     For the foregoing reasons, we hold the Board’s ac-
ceptance of Olympus’ submission of JP ’551 was harmless,
vacate and remand the Board’s determination that PST
failed to antedate JP ’551, and vacate the Board’s decision
invalidating claims 11, 38, 41–44, 46, 47, and 49 over
JP ’551 and remand for proceedings consistent with our
construction of the term “perforated.”
             VACATED AND REMANDED
                          COSTS
   Costs to PST.
  United States Court of Appeals
      for the Federal Circuit
                 ______________________

     PERFECT SURGICAL TECHNIQUES, INC.,
                 Appellant

                            v.

 OLYMPUS AMERICA, INC., OLYMPUS MEDICAL
         SYSTEMS CORPORATION,
                  Appellees
           ______________________

                       2015-2043
                 ______________________

    Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. IPR2014-
00233.
                 ______________________

SCHALL, Circuit Judge, concurring in part and dissenting
in part.
     I am pleased to join Parts A and C of the court’s opin-
ion. I respectfully dissent, however, from Part B. For the
reasons set forth below, I believe the Patent Trial and
Appeal Board (“Board”) applied the correct legal standard
in finding that Perfect Surgical Techniques, Inc. (“PST”)
failed to establish that Dr. Camran Nezhat, the inventor
named on U.S. Patent No. 6,030,384 (“the ’384 patent”),
exercised reasonably continuous diligence during the
critical period. I also believe the Board’s finding on
diligence is supported by substantial evidence.
2   PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



                            I.
                            A.
    The events leading to this appeal are not in dispute.
In March 1997, Dr. Nezhat retained attorney James
Heslin to prepare a patent application directed to bipolar
forceps for electrosurgery. On or about January 28, 1998,
Mr. Heslin sent an initial draft of the application to
Dr. Nezhat for his review. On March 2, 1998, Dr. Nezhat
returned comments on the initial draft to Mr. Heslin.
Mr. Heslin reviewed the comments two days later and
asked Dr. Nezhat for further explanation. On March 12,
Mr. Heslin sent Dr. Nezhat questions concerning the draft
application. Mr. Heslin and Dr. Nezhat then conferred on
March 16. After revising the application on April 7, Mr.
Heslin sent a revised draft to Dr. Nezhat on April 13.
Thereafter, on May 1, 1998, Mr. Heslin filed the applica-
tion at the U.S. Patent & Trademark Office, constructive-
ly reducing the invention to practice.
                            B.
    Olympus America, Inc. and Olympus Medical Systems
Corporation (collectively, “Olympus”) filed a petition for
inter partes review of certain claims of the ’384 patent.
J.A. 2. In its petition, Olympus relied on Japanese Unex-
amined Patent Application No. H10-33551 A (“JP ’551”),
which published on February 10, 1998. Id. 8, 13. During
the IPR, PST sought to antedate JP ’551 to disqualify it as
prior art. Id. 14–15. Specifically, PST asserted that Dr.
Nezhat had conceived of the claimed invention before JP
’551’s publication date and that he had been diligent in
constructively reducing his invention to practice. Id. To
demonstrate Dr. Nezhat’s conception and diligence, PST
submitted declarations and deposition testimony of
Dr. Nezhat and Mr. Heslin, among others. Id. 18.
   In assessing the evidence, the Board focused on Dr.
Nezhat’s activities and asked whether he had demon-
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.    3



strated “continuous exercise of reasonable diligence” in
reducing his invention to practice. Id. 16, 19, 22. In the
Board’s view, the evidence revealed several unexplained
“periods of inactivity” during the critical period. Id. 19–
20. For example, the Board found Dr. Nezhat unable to
identify any date on which he worked on the application
from January 28, 1998, to March 1, 1998—the period
during which the initial application was in his hands.
The Board also found that Dr. Nezhat could not pinpoint
any particular conflict during this time preventing him
from such work.        Id.   Thus, the Board explained,
Dr. Nezhat could not adequately account for roughly the
first three weeks of the critical period—i.e., from Febru-
ary 10, 1998, to March 1, 1998. Id. 20.
    Significantly, the Board found only two dates in the
entire critical period on which Dr. Nezhat took specific
actions towards preparing his application. The first date
was on March 2, 1998, when he submitted comments to
Mr. Heslin on the initial draft. Id. The second date was
on March 16, when he conferred with Mr. Heslin on
questions about the application. Id. 20–21. The Board
found no evidence, however, with respect to the nature of
Dr. Nezhat’s comments on the initial draft or with respect
to the conference. See id. As for Mr. Heslin’s testimony,
the Board determined that it was not specific as to facts
and dates and that it therefore could not establish
Dr. Nezhat’s diligence during periods of inactivity during
the critical period. Id. 21–22.
     Having considered the evidence, the Board found “at
least” three unexplained intervals of time during the
critical period with respect to which the evidence did not
establish diligence on Dr. Nezhat’s part—namely, the
intervals between February 10, 1998, and March 1, 1998
(“the First Gap”); March 12, 1998, and March 15, 1998
(“the Second Gap”); and April 13, 1998, and May 1, 1998
(“the Third Gap”). See id. 19, 22. Consequently, the
Board concluded that PST had offered insufficient evi-
4       PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



dence to establish Dr. Nezhat’s diligence during the entire
critical period.1 Id. 22.
                             C.
     In vacating the Board’s finding on diligence, the ma-
jority holds that the Board imposed an impermissibly
demanding standard on PST. According to the majority,
asking whether the inventor showed “continuous exercise
of reasonable diligence” is “too exacting and in conflict
with our precedent.” Ante, 7. In the majority’s view, as I
understand it, the proper standard is not whether an
inventor shows “continuous exercise of reasonable dili-
gence” during the critical period, but rather, whether the
inventor shows “reasonably continuous diligence” during
the critical period. Id. (emphases changed). Had the
Board applied the proper standard, the majority reasons,
it might have found sufficient diligence during the Second
and Third Gaps based on record evidence and actions
taken by Dr. Nezhat’s attorney. Id. 9–12.
                             II.
    After reviewing our cases and the record, I am not
persuaded that the Board imposed too exacting a stand-
ard on PST. And, while I share the majority’s reserva-
tions concerning the Board’s handling of the Second and
Third Gaps, in my view, the First Gap alone serves as
substantial evidence for the Board’s conclusion on dili-
gence.




    1   In light of its determination that PST failed to es-
tablish diligence as to the dates during which the applica-
tion was in Dr. Nezhat’s hands, the Board reasoned that
it need not separately address Mr. Heslin’s diligence or
the asserted conception date. Id. 18, 22.
PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.     5



                             A.
    To establish priority of an invention, a party must
show either an earlier reduction to practice or an earlier
conception followed by a diligent reduction to practice.
Purdue Pharma L.P. v. Boehringer Ingelheim GMBH, 237
F.3d 1359, 1365 (Fed. Cir. 2001); see also In re Steed, 802
F.3d 1311, 1316 (Fed. Cir. 2015) (“When the issue of
priority concerns the antedating of a reference, the appli-
cant is required to demonstrate, with sufficient documen-
tation, that the applicant was in possession of the later-
claimed invention before the effective date of the refer-
ence.”); Mahurkar v. C.R. Bard, Inc., 79 F.3d 1572, 1576–
78 (Fed. Cir. 1996) (explaining that a party attempting to
overcome anticipatory prior art has the burden to prove
an earlier date of invention). When a party relies on an
earlier conception (PST’s circumstance), it must “connect[]
the conception with [the inventor’s] reduction to practice
by reasonable diligence on his part, so that they are
substantially one continuous act.” Mahurkar, 79 F.3d at
1577 (quoting Christie v. Seybold, 55 F. 69, 76 (6th Cir.
1893)). The inventor must show diligence throughout the
entire critical period, which runs from a date just before
the prior art’s invention date to the inventor’s filing date.
See Creative Compounds, LLC v. Starmark Labs., 651
F.3d 1303, 1312–13 (Fed. Cir. 2011); Mahurkar, 79 F.3d
at 1578; 35 U.S.C. § 102(g) (2006) (“In determining priori-
ty of invention . . . there shall be considered . . . the rea-
sonable diligence of one who was first to conceive and last
to reduce to practice, from a time prior to conception by
the other.”). Determining whether an inventor shows
reasonable diligence is a “case specific inquiry.” Monsanto
Co. v. Mycogen Plant Sci., Inc., 261 F.3d 1356, 1369 (Fed.
Cir. 2001) (citing Jones v. Evans, 46 F.2d 197, 202
(C.C.P.A. 1931)).
    Our cases have framed the diligence inquiry in a vari-
ety of ways. The majority is correct that some of our cases
have asked whether an inventor showed “reasonably
6   PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.



continuous” diligence throughout the critical period. See,
e.g., Tyco Healthcare Grp. v. Ethicon Endo-Surgery, Inc.,
774 F.3d 968, 975 (Fed. Cir. 2014) (quoting Brown v.
Barbacid, 436 F.3d 1376, 1380 (Fed. Cir. 2006)) (“reason-
ably continuing activity”); Monsanto, 291 F.3d at 1370
(Fed. Cir. 2001) (“reasonably continuous [activity]”);
Jepson v. Egly, 231 F.2d 947, 957 (C.C.P.A. 1956) (“rea-
sonable continuous diligence”); Burns v. Curtis, 172 F.2d
588, 591 (C.C.P.A. 1949) (“reasonably continuous activi-
ty”).
    Other cases, however, have couched the test in differ-
ent terms. In Gould v. Schawlow, our predecessor court
asked whether an inventor’s testimony “support[s] a
finding of that continuity of activity which constitutes
reasonable diligence.” 363 F.2d 908, 916 (C.C.P.A. 1966)
(emphases added). In Griffith v. Kanamaru, we inquired
whether an inventor was “continuously or reasonably
diligent” during the critical period. 816 F.2d 624, 629
(Fed. Cir. 1987) (internal quotations omitted); see also
Scharmann v. Kassel, 179 F.2d 991, 996 (C.C.P.A. 1950)
(“continuing and reasonable diligence”) (citing Hull v.
Davenport, 90 F.2d 103 (C.C.P.A. 1937)). Still other cases
have used different expressions for the test. See, e.g.,
Mahurkar, 79 F.3d at 1577 (defining “reasonable dili-
gence” as “one continuous act”); Bey v. Kollonitsch, 806
F.2d 1024, 1030 (Fed. Cir. 1986) (requiring “reasonable
diligence during the continuous . . . critical period”). But
perhaps most importantly for our purposes here, our
predecessor court in In re McIntosh asked whether an
applicant showed “continuous exercise of reasonable
diligence.” 230 F.2d 615, 619 (C.C.P.A. 1956). This
standard is the same one recited by the Board. Ante, 7.
    It seems to me that, when taken together, our cases
suggest that the precise formulation of the diligence test
is relatively unimportant because its ultimate prescrip-
tion remains the same. What matters is that the party
seeking priority “account for the entire period during
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.    7



which diligence is required.” Creative Compounds, 651
F.3d at 1312–13 (citing Gould, 363 F.2d at 919). This
account must be “specific as to dates and facts” to estab-
lish diligence. Gould, 363 F.2d at 920. Gaps of inactivity
during the critical period do not automatically defeat a
finding of diligence so long as those gaps are adequately
explained. Monsanto, 261 F.3d at 1369 (“[T]here need not
necessarily be evidence of activity on every single day if a
satisfactory explanation is evidenced.”); see also Brown v.
Barton, 102 F.2d 193, 197 (C.C.P.A. 1939) (excusing
inactivity “due to reasonable excuses or reasons for failure
of action”); Scharmann, 179 F.2d at 997 (finding a lack of
diligence when gaps in the inventor’s activity were “not
adequately explained”). An inventor’s explanations for
inactivity must be corroborated. See Barbacid, 436 F.3d
at 1380 (citing In re Jolley, 308 F.3d 1317, 1328 (Fed. Cir.
2002)); Kendall v. Searles, 173 F.2d 986, 993 (C.C.P.A.
1949); see also Monsanto, 261 F.3d at 1369 (requiring a
“satisfactory explanation” to be “evidenced”). We assess
corroboration under a holistic “rule of reason,” Barbacid,
436 F.3d at 1380, but this standard is not so permissive
that it “dispense[s] with the requirements for some evi-
dence of independent corroboration.” Coleman v. Dines,
754 F.2d 353, 360 (Fed. Cir. 1985). Thus, as I understand
the law, establishing diligence requires that the inventor
account for his or her activities during the entire critical
period. Where there are stretches of inactivity, the inven-
tor must provide a reasonable justification for those gaps
with corroborating evidence.
     Against this backdrop, I am not persuaded that the
Board applied an inappropriate standard against PST.
The Board cited the diligence test from McIntosh and
asked whether Dr. Nezhat could account for “the entire
critical period.” J.A. 16. The Board then identified peri-
ods of inactivity and assessed the reasonableness of the
explanations provided, if any, for them. Id. 19–22. In
doing so, the Board searched for evidence corroborating
8   PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.



the offered justifications. Id. While this approach says
little about the accuracy of the Board’s conclusions (ad-
dressed in Part II.B. below), I cannot find error in these
contours of its methodology. Accordingly, I do not believe
the Board applied an improper standard in finding a lack
of diligence on the part of Dr. Nezhat.
    PST contends that the Board erred by placing an in-
ordinate focus on specific periods of inactivity rather than
on the entire critical period “as a whole.”        Appellant
Opening Br. 31. I do not agree. As I read them, our cases
turn on whether evidence supports a satisfactory explana-
tion for periods of inactivity. Monsanto, 261 F.3d at 1369.
Shorter gaps may be easier to explain than longer ones.
See, e.g., Barbacid, 436 F.3d at 1380–83 (determining that
six single-day gaps in a 31-day critical period did not
defeat a showing of reasonable diligence); Jolley, 308 F.3d
at 1327 (affirming the Board’s determination that “rea-
sonable everyday problems” excused gaps in the inventive
record); see also Monsanto, 261 F.3d at 1369. As the
majority points out, however, even a brief gap may give
rise to a requirement for some nominal justification or
explanation for the period. See ante, 8–9 (discussing In re
Mulder, 716 F.2d 1542 (Fed. Cir. 1983)). Inventors may
find longer periods of inactivity more difficult to defend.
See, e.g., In re Meyer Mfg. Corp., 411 F. App’x 316, 319–20
(Fed. Cir. 2010) (concluding that “an unexplained gap of
just over two months” supported the Board’s finding of
insufficient diligence); Gould, 363 F.2d at 919, 921 (hold-
ing that a lapse in activity of “nearly two months” defeat-
ed a claim of diligence); Morway v. Bondi, 203 F.2d 742,
749 (C.C.P.A 1953) (concluding that two separate “hia-
tus[es] of one and one-half months” did not constitute
“reasonable diligence in reducing the invention to practice
during the critical period”). But even long gaps can be
sustained if the explanations for them are sufficiently
reasonable. See, e.g., Rey-Bellet v. Engelhardt, 493 F.2d
1380, 1389 (C.C.P.A. 1974) (finding that “a shortage of
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.   9



monkeys and a limited ability to house them” justified a
three-month delay in testing); Reed v. Tornqvist, 436 F.2d
501, 504–05 (C.C.P.A. 1971) (determining that four weeks
of inactivity did not preclude a finding of diligence be-
cause it was excused by inventor’s vacation in Sweden
and the unexpected illness of the inventor’s father). In
each of these cases, the court focused on identified gaps
and asked whether they were reasonable under the cir-
cumstances. I cannot fault the Board for taking a similar
approach in PST’s case.
     In my view, the Board’s approach was consistent with
our law. In several places in its decision, the Board
evaluated not just the existence of the identified gap
periods, but also whether the record reasonably justified
them. For example, the Board searched for evidence of
Dr. Nezhat’s surgery schedule, potential teaching con-
flicts, the “nature of [the] comments” which took him over
a month to prepare, any explanation offered by PST for
the Third Gap, and other such evidence. E.g., J.A. 20–21.
This kind of information, I think, speaks to the reasona-
bleness of the gaps of inactivity. Indeed, the Board ex-
pressly sought this information to gauge “the
reasonableness of any gaps in [Dr. Nezhat’s] activity and
explanations for such periods of inactivity.” Id. 20.
    In sum, I believe the Board’s approach of identifying
gap periods and assessing their reasonableness in light of
corroborating evidence was consistent with our precedent.
Therefore, I believe the Board applied an appropriate
standard in appraising Dr. Nezhat’s diligence.
                           B.
    Turning now to the substance of the Board’s findings,
the Board found three periods of inactivity purportedly
attributable to Dr. Nezhat in its Final Written Decision:
the First Gap (spanning the publication of JP ’551 to Dr.
Nezhat’s submission of comments to Mr. Heslin), the
Second Gap (spanning a weekend), and the Third Gap
10   PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



(spanning Mr. Heslin’s transmission of a revised draft to
Dr. Nezhat to filing).
    We review the Board’s factual findings on diligence
for substantial evidence. Monsanto, 261 F.3d at 1369.
Substantial evidence justifies a finding if a reasonable
mind might accept the evidence to support it. Consol.
Edison Co. v. NLRB, 305 U.S. 197, 229 (1938). This
standard involves an examination of the record as a
whole, taking into account evidence supporting and
detracting from an agency’s finding. Universal Camera
Corp. v. NLRB, 340 U.S. 474, 487–88 (1951). Substantial
evidence does not require the Board’s finding to be the
only one possible from the record so long as it is reasona-
ble. “[T]he possibility of drawing two inconsistent conclu-
sions from the evidence does not prevent [a] finding from
being supported by substantial evidence.” In re Gartside,
203 F.3d 1305, 1312 (Fed. Cir. 2000) (quoting Consolo v.
Fed. Maritime Comm’n, 383 U.S. 607, 620 (1966)); see also
Jolley, 308 F.3d at 1320 (“If the evidence in record will
support several reasonable but contradictory conclusions,
we will not find the Board’s decision unsupported by
substantial evidence simply because the Board chose one
conclusion over another plausible alternative.”).
                             1.
    At the outset, I agree with the majority that the
Board’s treatment of the Second and Third Gaps is trou-
bling. As the majority observes, the Second Gap reflects a
three-day period spanning a weekend. Ante, 11–12.
Immediately preceding this weekend, Dr. Nezhat and Mr.
Heslin actively communicated about the invention. Id.
And immediately afterward, they held a conference to
discuss it. Id. Given the short duration of this period, its
status as a weekend, and the inventor’s activities sur-
rounding it, I share the majority’s position on the unrea-
sonableness of the Board in basing its diligence finding on
the Second Gap. Id.
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.   11



    I also agree with the majority in faulting the Board
for failing to consider Mr. Heslin’s activities during the
Third Gap. Id. 10–11. An attorney’s diligence is imputa-
ble to the inventor. E.g., Bey, 806 F.3d at 1027. Mr.
Heslin undertook actions during the Third Gap that could
be attributed to Dr. Nezhat, such as preparing an infor-
mation disclosure statement and finalizing the applica-
tion. Ante, 11. Had the Board investigated Mr. Heslin’s
actions, it may have arrived at a different conclusion on
Dr. Nezhat’s diligence during the Third Gap. Accordingly,
I agree that it was error for the Board to disregard Mr.
Heslin’s activities during the critical period.
                            2.
    I part company with the majority, however, in regard
to the First Gap. In my view, the First Gap alone consti-
tutes substantial evidence for the Board’s ultimate find-
ing on diligence, as it establishes that PST did not meet
its burden of “account[ing] for the entire period during
which diligence is required.” Creative Compounds, 651
F.3d at 1312–13 (emphasis added). PST does not try to
justify this delay with corroborating evidence. And be-
cause the First Gap is a 19-day period during which Dr.
Nezhat indisputably controlled the draft application, none
of the Board’s errors noted above impact its findings on
this gap.
     PST does not contest the Board’s finding that there
was an absence of activity during the period of the First
Gap. PST in fact concedes “there was no evidence of
‘diligence’ during the periods of inactivity” identified by
the Board. Appellant Reply Br. 13 (emphasis added).
That concession, I think, is justified by the record. As I
see it, the question here boils down to whether, after
viewing the evidence, the Board was unreasonable in
finding that an unexplained gap in activity lasting nearly
three weeks was sufficient to show a lack of diligence. In
my view, a reasonable mind might conclude that it was.
12   PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.



     For example, in Rieser v. Williams, 255 F.2d 419, 424
(C.C.P.A. 1958), our predecessor court affirmed a finding
of the Board of Patent Interferences (“BPI”) that an
inventor failed to show diligence during a 13-day stretch
of the critical period. We explained that, “even aside from
the question of corroboration,” the testimony of the inven-
tor did “not show that he was doing anything toward
preparing or filing his application during a period of a
month or more immediately preceding [another party’s]
entry into the field.” Id. Similarly, in Gould, the court
affirmed the BPI’s award of priority to a senior party (i.e.,
the party first reducing an invention to practice) because
it concluded that the junior party had failed to establish
diligence. 363 F.2d at 919, 921. According to the court,
the junior party did not “account for the entire period
during which diligence [was] required,” as his testimony
did not explain a potential lapse in activity of nearly two
months with specific “dates and facts.” Id. at 919–20.
Other diligence cases from this court and its predecessor
have involved unexplained gaps of similar lengths and
reached the same conclusion. See, e.g., Meyer, 411 F.
App’x at 319–20 (affirming the Board’s finding that “an
unexplained gap of just over two months” defeated dili-
gence claim); Ireland v. Smith, 97 F.2d 95, 99–100
(C.C.P.A. 1938) (determining that an appellant failed to
establish diligence because there was “no proof in the
record” of activity during a 25-day stretch of the critical
period); Morway, 203 F.2d at 749 (concluding that sepa-
rate, unexplained gaps of “one and one-half months” did
not constitute reasonable diligence).
    I recognize that the First Gap of unexplained inactivi-
ty here—which is part of a larger period of inactivity
extending from the end of January until March 1—is
generally shorter than the gaps in the aforementioned
cases. But see Rieser, 255 F.2d at 424 (requiring the
inventor to show activity during an initial 13-day span of
the critical period). Still, given that the First Gap and the
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.   13



periods of inactivity in those cases are roughly the same
size, it seems to me that the Board’s conclusion that the
First Gap amounted to an unreasonable break in activity
is consistent with our cases. Compare, e.g., Rieser, 225
F.2d at 424 (determining that an unexplained 13-day
period of inactivity defeated a diligence claim) with Bar-
bacid, 436 F.3d at 1380–82 (determining that six single-
day gaps in a 31-day critical period did not preclude a
showing of diligence).
     Notably, PST may have established diligence in this
case had it provided a “satisfactory explanation” for Dr.
Nezhat’s inactivity with corroborating evidence. Monsan-
to, 261 F.3d at 1369. Indeed, courts have confronted idle
periods longer than the First Gap and found that they did
not preclude a showing of diligence. See, e.g., Rey-Bellet,
493 F.2d at 1389 (three months); Tornqvist, 436 F.2d at
504–05 (four weeks). But here, PST’s only excuse for Dr.
Nezhat’s inactivity during the First Gap is that he had
other “professional commitments” and needed time “for
study of the application.” Appellant Opening Br. 33.
Although an “excuse for inactivity” may include “reasona-
ble everyday problems and limitations,” Griffith, 816 F.2d
at 626–27, PST offered no evidence of such problems and
limitations other than Dr. Nezhat’s uncorroborated testi-
mony. The Board found, and PST does not dispute, that
the record does not include evidence during the First Gap
as to Dr. Nezhat’s activities at all, let alone evidence
“specific as to facts and dates” explaining nearly three
weeks of inactivity during the critical period. See Gould,
363 F.2d at 920. On this record, I think a reasonable
mind might find PST’s explanation unsatisfactory.
    PST also failed to produce any evidence corroborating
its justification for the First Gap. Given Dr. Nezhat’s
claims that he “performed approximately four to six
surgeries per week” and “worked an average of 80 hours
each week,” Appellant Opening Br. 7, one would have
expected the record to show medical records or testimony
14       PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.



from independent witnesses supporting these points. But
PST provided none, and I do not see any indication that
PST attempted to locate such evidence. 2 While I am
sympathetic to PST’s predicament of unearthing evidence
from 1998, as the junior party it ultimately bears the
burden of proving diligence. E.g., Price v. Symsek, 988
F.2d 1187, 1190–91 (Fed. Cir. 1993); Scharmann, 179
F.2d at 996.
    The Board also found that “[n]o evidence is presented
as to the nature of [the] comments” Dr. Nezhat returned
to Mr. Heslin on March 2. J.A. 20. As I see it, this omis-
sion is noteworthy because it leaves open several scenari-
os under which the Board could have reasonably
concluded that Dr. Nezhat was not diligent. For example,
after receiving the draft on or about January 28, Dr.
Nezhat could have read it, prepared comments that day,
and then sat on the comments for over a month before
eventually sending them to Mr. Heslin. Alternatively, he
could have set aside the application and waited until
March 2 to review it and prepare comments. The record
simply does not indicate what was done and when it was
done.




     2  The majority is correct that corroboration “may be
provided by sufficient independent circumstantial evi-
dence.” Ante, 9 (quoting Jolley, 308 F.3d at 1328). Here,
however, PST has not provided any such independent
circumstantial evidence with respect Dr. Nezhat’s profes-
sional or academic commitments during the First Gap.
Cf. Jolley, 308 F.3d at 1328 (relying on testimony from
three independent witnesses to corroborate an inventor’s
diligence). At the same time, the majority’s discussion on
this score relates to Dr. Nezhat’s activities around the
Second Gap, not the First. Ante, 9–10.
PERFECT SURGICAL TECHNIQUES   v. OLYMPUS AMERICA, INC.   15



    Further, PST’s inability to substantiate the extent of
Dr. Nezhat’s comments limited the Board’s ability to
glean his diligence through inference. Had the record
shown Dr. Nezhat making substantial remarks on the
draft application, providing detailed questions to Mr.
Heslin, or taking other such strides, the Board may have
been able to discern Dr. Nezhat’s diligence during the
First Gap. Without such evidence before it, however, I do
not believe the Board can be faulted for not concluding
that Dr. Nezhat was diligent during the period of the
First Gap. 3
    I do not find any of PST’s arguments persuasive. PST
is correct that the Board should have considered the
actions of Mr. Heslin in evaluating his diligence, but these
activities are irrelevant to the First Gap. During the
period of the First Gap, the draft application was unques-



   3    In its discussion of the Second Gap, the majority
points to a sentence in a March 12 letter from Mr. Heslin
to Dr. Nezhat as potentially evincing Dr. Nezhat’s March
2 comments. Ante, 12 (citing J.A. 927). This letter does
not change my opinion for several reasons. First, I am
unable to locate in the briefing (here or below) where PST
relied on this letter as substantiating Dr. Nezhat’s activi-
ties during the First Gap. Indeed, as noted, the majority
discusses this letter in the context of the unreasonable-
ness of the Board’s conclusion concerning the Second Gap.
Id. Second, I am unable to conclude that this passing
remark necessarily justifies a 19-day gap in the critical
period. The record shows that Dr. Nezhat could not
account for his activities during this time, provided no
evidence corroborating his schedule or the submitted
comments, and never contacted Mr. Heslin within this
timeframe. On these facts, I cannot conclude that a
reasonable mind would have arrived at a conclusion
different from that of the Board.
16   PERFECT SURGICAL TECHNIQUES    v. OLYMPUS AMERICA, INC.



tionably in Dr. Nezhat’s hands and PST does not rely on
Mr. Heslin’s actions for establishing diligence during that
period.
     PST also is correct that the “rule of reason” required
the Board to evaluate all the pertinent evidence as a
whole. Appellant Br. 21–22. But this rule does not
dispense with the twin requirements that (1) the evidence
must still reasonably justify gaps in the inventor’s activity
and (2) the justification must be corroborated with inde-
pendent evidence. By shifting its focus to the entire
critical period generally, rather than pockets of inactivity
in particular, PST overlooks that it still must provide an
evidenced, satisfactory explanation for the First Gap.
Scharmann, 179 F.2d at 996–97. PST’s briefing does not
include a detailed explanation for the First Gap, and its
vague allusion to Dr. Nezhat’s hectic schedule and “care-
ful review” of the draft is uncorroborated with independ-
ent evidence.
    To conclude, I believe substantial evidence supports
the Board’s finding that Dr. Nezhat failed to demonstrate
reasonable diligence during the entire critical period. I
therefore respectfully dissent from the majority’s decision
on this point. Accordingly, while I agree that we should
vacate the Board’s decision and remand the case to the
Board for further proceedings, I would limit the remand
proceedings to determining whether, under the correct
claim construction, the invention claimed in the ’384
patent is anticipated or rendered obvious in view of JP
’551.
