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 review (“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 translate 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 Olympus’ 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 dispute 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 antedate a reference by proving earlier conception and reasonable 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 February 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 reviewed the second draft” before it was finalized and filed 

on May 1. J.A. 687. 

An inventor’s testimony regarding his reasonable diligence must be corroborated by evidence. Brown v. Barbacid, 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 testified 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 expressed 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 corroborating 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 therefore 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 characterized 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 “continuous and corroborated diligence”); J.A. 18 (“Patent Owner 

does not provide sufficient evidence to demonstrate . . . 

that Dr. Nezhat continuously exercised reasonable diligence 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 evidence to demonstrate Dr. Nezhat’s continuous exercise of 

reasonable diligence . . . .”). The standard demanded by 

the Board is too exacting and in conflict with our precedent. 

A patent owner need not prove the inventor continuously exercised reasonable diligence throughout the 

critical period; it must show there was reasonably continuous 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 example, 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 purpose 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 “performed 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 corroboration 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 evidence 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 dismissing 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, therefore, do not address whether Patent Owner provides 

sufficient evidence to demonstrate Mr. Heslin’s continuous exercise of reasonable diligence for the entire critical 

period.”). This was error. An attorney’s work in preparing 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 constructively 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 occurred 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 documents on May 1. J.A. 604. And Mr. Heslin testified that 

it was his usual practice to dictate the text of the application and allow time, around eight days, for word processing 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 considering 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 presented 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” regarding 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 another 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 embodiments and described their benefits both in terms of 

increased electrode area and enhanced current containment.” 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 amounted 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 evidence, 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 testimony 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 (quoting ’384 patent at 3:25–27). The Board cited extrinsic 

dictionary definitions in support, including that to “perforate” 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 extrinsic evidence, namely dictionary definitions which supported 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 “passages.” 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 acceptance 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 opinion. 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 application at the U.S. Patent & Trademark Office, constructively 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 Unexamined 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 February 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 majority 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 diligence” 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 standard on PST. And, while I share the majority’s reservations 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 diligence. 

 

1 In light of its determination that PST failed to establish diligence as to the dates during which the application 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 applicant is required to demonstrate, with sufficient documentation, that the applicant was in possession of the laterclaimed invention before the effective date of the reference.”); 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 priority of invention . . . there shall be considered . . . the reasonable 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 variety 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)) (“reasonably 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) (“reasonable continuous diligence”); Burns v. Curtis, 172 F.2d 

588, 591 (C.C.P.A. 1949) (“reasonably continuous activity”).

Other cases, however, have couched the test in different 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 diligence” 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 prescription 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 establish 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 evidence 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 inventor 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 periods 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 (addressed 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 inordinate 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 explanation 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 “reasonable 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 (holding that a lapse in activity of “nearly two months” defeated a claim of diligence); Morway v. Bondi, 203 F.2d 742, 

749 (C.C.P.A 1953) (concluding that two separate “hiatus[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 because 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 circumstances. 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 conflicts, 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 reasonableness of the gaps of inactivity. Indeed, the Board expressly 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 reasonable. “[T]he possibility of drawing two inconsistent conclusions 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 troubling. 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 surrounding it, I share the majority’s position on the unreasonableness 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 imputable 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 information disclosure statement and finalizing the application. 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 constitutes substantial evidence for the Board’s ultimate finding 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 because 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 inventor 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 diligence 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 separate, unexplained gaps of “one and one-half months” did 

not constitute reasonable diligence).

I recognize that the First Gap of unexplained inactivity 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 Barbacid, 436 F.3d at 1380–82 (determining that six singleday 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. Monsanto, 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 “reasonable 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 testimony. 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 omission is noteworthy because it leaves open several scenarios 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 evidence.” 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 professional 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 activities during the First Gap. Indeed, as noted, the majority 

discusses this letter in the context of the unreasonableness 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 independent 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 “careful review” of the draft is uncorroborated with independent 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.