Egenera, Inc. v. Cisco Systems, Inc.

Case: 19-2015 Document: 68 Page: 1 Filed: 08/28/2020

United States Court of Appeals
for the Federal Circuit
______________________

EGENERA, INC.,
Plaintiff-Appellant

v.

CISCO SYSTEMS, INC.,
Defendant-Appellee
______________________

2019-2015, 2019-2387
______________________

Appeals from the United States District Court for the
District of Massachusetts in No. 1:16-cv-11613-RGS, Judge
Richard G. Stearns.
______________________

Decided: August 28, 2020
______________________

DAN L. BAGATELL, Perkins Coie LLP, Hanover, NH, ar-
gued for plaintiff-appellant. Also represented by ANDREW
DUFRESNE, Madison, WI; MARTIN GILMORE, New York, NY;
JOHN BRUCE CAMPBELL, JAMES ELROY QUIGLEY, JOEL
LANCE THOLLANDER, McKool Smith, PC, Austin, TX;
CHRISTOPHER THOR BOVENKAMP, Dallas, TX.

E. JOSHUA ROSENKRANZ, Orrick, Herrington & Sutcliffe
LLP, New York, NY, argued for defendant-appellee. Also
represented by EDMUND HIRSCHFELD, DANIEL A. RUBENS;
ELIZABETH MOULTON, Menlo Park, CA; MARK S. DAVIES,
ETHAN P. FALLON, ANNE SAVIN, Washington, DC; BRIAN
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2 EGENERA, INC. v. CISCO SYSTEMS, INC.

LEARY, JONAS R. MCDAVIT, TAMIR PACKIN, Desmarais LLP,
New York, NY.
______________________

Before PROST, Chief Judge, REYNA and STOLL, Circuit
Judges.
PROST, Chief Judge.
Egenera, Inc. (“Egenera”) sued Cisco Systems, Inc.
(“Cisco”) in the United States District Court for the District
of Massachusetts, alleging that Cisco’s enterprise server
systems infringe various claims of U.S. Patent
No. 7,231,430 (“the ’430 patent”).
Prior to claim construction, and alongside an ongoing
inter partes review (“IPR”) proceeding, Egenera separately
petitioned the United States Patent and Trademark Office
(“PTO”) to remove one of the eleven listed inventors from
the ’430 patent. Following the district court’s claim con-
struction and a trial on inventorship, Egenera asked the
district court to add the removed inventor back to the pa-
tent. The district court determined that judicial estoppel
prevented Egenera from relisting the inventor and held the
’430 patent invalid for failing to name all inventors. See
Egenera, Inc. v. Cisco Sys., Inc., 379 F. Supp. 3d 110
(D. Mass. 2019) (“Invalidity Decision”); Egenera, Inc.
v. Cisco Sys., Inc., 348 F. Supp. 3d 99 (D. Mass. 2019) (“Ju-
dicial Estoppel Decision”); Egenera, Inc. v. Cisco Sys., Inc.,
No. 16-11613, 2018 WL 717342 (D. Mass. Feb. 5, 2018)
(“Claim Construction Decision”).
Egenera appeals, challenging both the district court’s
claim construction and the application of judicial estoppel.
For the reasons described below, we affirm the district
court’s claim construction but vacate the invalidity judg-
ment based on judicial estoppel and remand for further
proceedings.
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EGENERA, INC. v. CISCO SYSTEMS, INC. 3

BACKGROUND
I
Egenera owns the ’430 patent, which claims a platform
for automatically deploying a scalable and reconfigurable
virtual network.
In April 2001, Egenera filed a provisional application
that resulted in four nonprovisional applications contain-
ing the same specification. One of them resulted in the
’430 patent, covering the “overarching system architec-
ture.” Appellant’s Br. 12.
According to the ’430 patent’s specification, it is diffi-
cult to anticipate the amount of computing power required
in a large organization’s physical computer network, and
manually upgrading or deploying new physical servers is
slow and expensive. See generally ’430 patent col. 1
ll. 21–61. To address this, the claimed system creates a
quickly reconfigurable virtual network environment plat-
form. The platform “provides a large pool of processors” for
the virtual network to use. Id. at col. 2 ll. 47–52. A subset
may be “selected and configured” to form a “virtualized net-
work” (or, “processing area network”) to “serve a given set
of applications or customer.” Id. Accordingly, “processing
resources may be deployed rapidly and easily through soft-
ware” instead of through physical reconfiguration. Id.
at col. 2 ll. 57–62.
Claim 1, which is representative, reads:
1. A platform for automatically deploying at least
one virtual processing area network, in response to
software commands, said platform comprising:
a plurality of computer processors connected to an
internal communication network;
at least one control node in communication with an
external communication network and in communi-
cation with an external storage network having an
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4 EGENERA, INC. v. CISCO SYSTEMS, INC.

external storage address space, wherein the at
least one control node is connected to the internal
communication network and thereby in communi-
cation with the plurality of computer processors,
said at least one control node including logic to re-
ceive messages from the plurality of computer pro-
cessors, wherein said received messages are
addressed to the external communication network
and to the external storage network and said at
least one control node including logic to modify said
received messages to transmit said modified mes-
sages to the external communication network and to
the external storage network;
configuration logic for receiving and responding to
said software commands, said software commands
specifying (i) a number of processors for a virtual
processing area network (ii) a virtual local area
network topology defining interconnectivity and
switching functionality among the specified proces-
sors of the virtual processing area network, and
(iii) a virtual storage space for the virtual pro-
cessing area network, said configuration logic in-
cluding logic to select, under programmatic control,
a corresponding set of computer processors from
the plurality of computer processors, to program
said corresponding set of computer processors and
the internal communication network to establish
the specified virtual local area network topology,
and to program the at least one control node to de-
fine a virtual storage space for the virtual pro-
cessing area network, said virtual storage space
having a defined correspondence to a subset of the
external storage address space of the external stor-
age network; and
wherein the plurality of computer processors and
the at least one control node include network
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EGENERA, INC. v. CISCO SYSTEMS, INC. 5

emulation logic to emulate Ethernet functionality
over the internal communication network.
’430 patent claim 1 (emphasis added).
In this case, the construction of “logic to modify” is at
issue in the context of “at least one control node . . . includ-
ing logic to modify . . . received messages to transmit said
modified messages to the external communication net-
work.”
Processors used by the virtual network may generate
messages to be sent outside the network. But the outside
network may use different protocols, see Invalidity Deci-
sion, 379 F. Supp. 3d at 125, and so there must be a way to
modify outbound messages so that those messages will be
compatible with the external network. This is done by the
“logic to modify” within the “control node.” See ’430 patent
claim 1.
II
Egenera sued Cisco in August 2016 for infringement of
the ’430 patent. In response, Cisco filed an IPR petition
challenging all eight of the patent’s claims.
According to Egenera, upon reviewing the ’430 patent
after Cisco’s IPR petition, it realized that all claim limita-
tions had been conceived before one listed inventor, Mr. Pe-
ter Schulter, had started working there. Appellant’s Br.
18–19. Mr. Schulter had been hired by Egenera during the
invention’s development for his “extensive networking ex-
perience” and to “refine and code the networking subsys-
tem” of the invention. Id. at 11; Invalidity Decision, 379 F.
Supp. 3d at 118. And so, one month after responding to the
IPR petition, Egenera separately petitioned the PTO to re-
move Mr. Schulter as a listed inventor. Judicial Estoppel
Decision, 348 F. Supp. 3d at 101; J.A. 9367–80. By then,
Mr. Schulter, as well as most of the named inventors, no
longer worked for Egenera. It is apparent that at least part
of Egenera’s motivation to remove Mr. Schulter was to
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6 EGENERA, INC. v. CISCO SYSTEMS, INC.

facilitate swearing behind “Grosner,” a piece of prior art
asserted against Egenera in the IPR. See Invalidity Deci-
sion, 379 F. Supp. 3d at 114. Grosner’s priority date was
November 2, 2000. Id. at 113. And Mr. Schulter joined
Egenera on October 2, 2000. Id. at 112. But Egenera ar-
gued an even-earlier conception date of September 29,
2000. Id. at 114.
While the inventorship petition was pending, the
Board declined to institute Cisco’s IPR. J.A. 10912–28. In
so doing, it assumed Grosner was prior art but neverthe-
less concluded that Cisco had not met its burden of estab-
lishing a reasonable likelihood of prevailing on the merits.
J.A. 10922. Shortly thereafter, in January 2018, the PTO
granted Egenera’s petition and removed Mr. Schulter’s
name. J.A. 9387.
Cisco had not argued that any of the “logic” terms
should be interpreted as means-plus-function in the IPR,
nor in its invalidity contentions. E.g., J.A. 10368,
12412–14. But it advanced a means-plus-function con-
struction at the district court. And in February 2018, the
district court issued an order construing the patent’s “logic”
terms as means-plus-function elements. Claim Construc-
tion Decision, 2018 WL 717342, at *1, *4–10. It concluded
that the structure in the specification corresponding to the
claimed function of the “logic to modify” was the so-called
tripartite structure—the combination of a virtual LAN
proxy, a physical LAN driver, and a virtual LAN server.
Id. at *6–7; Invalidity Decision, 379 F. Supp. 3d at 128.
Cisco next filed an amended answer in the district
court asserting invalidity based on pre–America Invents
Act (“AIA”) § 102(f)—contending that Mr. Schulter in-
vented the tripartite structure, and therefore that the pa-
tent did not list all inventors. J.A. 3238, 3251. In
August 2018, Cisco moved for summary judgment of inva-
lidity on this ground, which the district court denied, find-
ing triable issues of fact regarding inventorship. Judicial
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EGENERA, INC. v. CISCO SYSTEMS, INC. 7

Estoppel Decision, 348 F. Supp. 3d at 108–09. But the court
also rejected Egenera’s argument that if the trial showed
Mr. Schulter to be an inventor, the patent’s inventorship
should be corrected under 35 U.S.C. § 256(b). Id.
at 101–02. The court reasoned that judicial estoppel pre-
cluded Egenera from “resurrect[ing]” Mr. Schulter’s inven-
torship. Id. at 102.
The court conducted a three-day bench trial on inven-
torship. Invalidity Decision, 379 F. Supp. 3d at 112. The
court found, in Cisco’s favor, that Mr. Schulter had con-
ceived the tripartite structure. Id. at 125–29. The court
then reiterated that Egenera was judicially estopped from
invoking § 256 to restore Mr. Schulter’s name, thereby
holding the ’430 patent invalid. Id. at 129.
Egenera appealed the invalidity judgment, challenging
the underlying construction of “logic to modify” and the ap-
plication of judicial estoppel. We have jurisdiction under
28 U.S.C. § 1295(a)(1).
DISCUSSION
I
First we address Egenera’s contention that the district
court’s claim construction was wrong.
At issue is the “logic to modify” limitation, which the
district court construed as a means-plus-function element.
For the reasons below, we agree with the district court’s
claim construction.
The ultimate interpretation of a patent claim is a legal
question that we review de novo. Williamson v. Citrix
Online, LLC, 792 F.3d 1339, 1346 (Fed. Cir. 2015) (citing
Teva Pharm. USA, Inc. v. Sandoz, Inc., 574 U.S. 318,
331–32 (2015)). To the extent the district court makes un-
derlying findings of fact based on extrinsic evidence, we re-
view them for clear error. Id.
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8 EGENERA, INC. v. CISCO SYSTEMS, INC.

Means-plus-function claiming occurs when a claim
term invokes 35 U.S.C. § 112(f), 1 which states:
An element in a claim for a combination may be ex-
pressed as a means or step for performing a speci-
fied function without the recital of structure,
material, or acts in support thereof, and such claim
shall be construed to cover the corresponding struc-
ture, material, or acts described in the specification
and equivalents thereof.
We presume that claim terms with the word “means”
invoke § 112(f) and that claim terms without the word
“means” do not. Williamson, 792 F.3d at 1348 (en banc). 2
This presumption, however, does not permit patentees to
freely engage in functional claiming while circumventing
§ 112(f) simply by avoiding the word “means,” as we clari-
fied in Williamson. See id. at 1349 (warning of “a prolifer-
ation of functional claiming . . . free of the strictures set
forth in the statute”). And so the presumption against
means-plus-function interpretation is rebuttable if a chal-
lenger demonstrates that a claim term either fails to “recite
sufficiently definite structure” or recites “function without
reciting sufficient structure for performing that function.”
Id. (quoting Watts v. XL Sys., Inc., 232 F.3d 877, 880
(Fed. Cir. 2000)).
We clarified in Williamson that the presumption
against means-plus-function claiming is not “strong” and
that a challenger need not show that the limitation is “es-
sentially . . . devoid of anything that can be construed as

1 Although pre-AIA § 112, ¶ 6, applies in this case,
the AIA recodified that provision as § 112(f). We use the
AIA numbering for convenience.
2 The discussion in Williamson of the applicability of
§ 112(f) was joined by the en banc court. 792 F.3d
at 1347–49 & n.3.
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EGENERA, INC. v. CISCO SYSTEMS, INC. 9

structure.” Id. Rather, a challenger need only show that
the structure is not “sufficient.” See id.; TEK Glob., S.R.L.
v. Sealant Sys. Int’l, Inc., 920 F.3d 777, 785 (Fed. Cir.
2019). For example, “[g]eneric terms such as ‘mechanism,’
‘element,’ ‘device,’ and other . . . verbal constructs may be
used in a claim in a manner that is tantamount to using
the word ‘means’ because they ‘typically do not connote suf-
ficiently definite structure’ and therefore may invoke
[§ 112(f)].” Williamson, 792 F.3d at 1350 (quoting Mass.
Inst. of Tech. v. Abacus Software, 462 F.3d 1344, 1354
(Fed. Cir. 2006)). Such terms may amount to “generic
terms or black box recitations of structure or abstractions.”
MTD Prods. v. Iancu, 933 F.3d 1336, 1341 (Fed. Cir. 2019)
(quoting Zeroclick, LLC v. Apple Inc., 891 F.3d 1003, 1008
(Fed. Cir. 2018)). Or a term may amount to a coined “nonce
word”—that is, a word “invented . . . for one occasion only.”
See Bryan A. Garner, Garner’s Modern English Usage 1016
(4th ed. 2016); Webster’s Third New International Diction-
ary (1961) (defining “nonce word” as “a word . . . coined and
used apparently to suit one particular occasion . . . but not
adopted into use generally”); Lighting World, Inc. v. Birch-
wood Lighting, Inc., 382 F.3d 1354, 1360 (Fed. Cir. 2004)
(noting that either a “generic structural term” or a “coined
term” can invoke § 112(f)).
If the presumption against means-plus-function inter-
pretation is overcome, we must “identify the claimed func-
tion” and then “determine what structure, if any, disclosed
in the specification corresponds to the claimed function.”
Williamson, 792 F.3d at 1351. These are questions of law,
reviewed de novo. Kemco Sales, Inc. v. Control Papers Co.,
208 F.3d 1352, 1360 (Fed. Cir. 2000).
“To determine whether the claim limitation at issue
connotes sufficiently definite structure to a person of ordi-
nary skill in the art, we look first to intrinsic evidence, and
then, if necessary, to the extrinsic evidence.” TEK Glob.,
920 F.3d at 785 (citing Phillips v. AWH Corp., 415 F.3d
1303 (Fed. Cir. 2005) (en banc)).
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10 EGENERA, INC. v. CISCO SYSTEMS, INC.

A
Egenera insists that the district court erred in constru-
ing “logic to modify” as a means-plus-function limitation.
The ’430 patent contains several “logic” terms. The dis-
trict court construed them all as means-plus-function;
Egenera challenges only the construction of “logic to modify
said received messages to transmit said modified messages
to the external communication network and to the external
storage network.”
1
The district court observed that, in the claim language,
each “logic” term was “described by a specific function” and
was unaccompanied by “structural components.” Claim
Construction Decision, 2018 WL 717342, at *5.
Examining the intrinsic evidence, the district court ex-
plained that “[t]he specification discloses that ‘logic’ has to
be implemented,” id. (citing ’430 patent col. 23 ll. 23–24,
col. 25 ll. 3–4), and that such implemented logic could be
“software logic” or “BIOS-based,” id. (citing ’430 patent
col. 3 ll. 61, 63, col. 6 l. 18). The court concluded that the
specification was then “consistent with an understanding
of logic as an abstraction for the set of steps designed to
accomplish a stated function.” Id.
Egenera had argued that “logic” denotes “software,
firmware, circuitry, or some combination thereof.” Id.
at *4. The district court noted that Egenera’s favored def-
inition was itself “so broad and formless as to be a generic
black box for performing the recited computer-imple-
mented functions.” Id. at *6 (cleaned up).
Accordingly, the court concluded that the totality of the
evidence rebutted the presumption against means-plus-
function claiming.
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EGENERA, INC. v. CISCO SYSTEMS, INC. 11

2
On appeal, Egenera, pointing to its expert’s explana-
tion and dictionary definitions, argues that “‘logic’ is a com-
mon term of art meaning software, firmware, circuitry, or
[a] combination thereof.” Appellant’s Br. 51. As Cisco ar-
gues, “logic” as used in the claims means only a “general
category of whatever may perform” the function. Appel-
lee’s Br. 58, 62; cf. Williamson, 792 F.3d at 1350
(“‘[M]odule’ is simply a generic description for software or
hardware that performs a specified function.”).
The question is not whether a claim term recites any
structure but whether it recites sufficient structure—a
claim term is subject to § 112(f) if it recites “function with-
out reciting sufficient structure for performing that func-
tion.” Williamson, 792 F.3d at 1348 (emphasis added)
(quoting Watts, 232 F.3d at 880). Egenera does not explain
how its “logic”—even assuming it connotes some possible
structure in the general sense of software, firmware, or cir-
cuitry—amounts to “sufficient structure for performing
[the modification] function.” See id. (emphasis added).
Egenera also argues that the “larger claim context” in-
dicates that “logic” is structural because the “logic to mod-
ify” is part of a supposedly structural component—the
“control node.” Appellant’s Br. 52; Reply Br. 22. But that
is not enough. Mere inclusion of a limitation within a
structure does not automatically render the limitation it-
self sufficiently structural. And, again, the question is not
whether “logic” is utterly devoid of structure but whether
the claim term recites sufficient structure to perform the
claimed functions.
Egenera next argues that the claim language defines
the “inputs, outputs, connections, and operation” of the
logic component. Appellant’s Br. 52–54 (citing Apple Inc.
v. Motorola, Inc., 757 F.3d 1286, 1299–303 (Fed. Cir. 2014);
Linear Tech. Corp. v. Impala Linear Corp., 379 F.3d 1311,
1319–21 (Fed. Cir. 2004); Mass. Inst. of Tech., 462 F.3d
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12 EGENERA, INC. v. CISCO SYSTEMS, INC.

at 1355–56; and Lighting World, 382 F.3d at 1359–63); Re-
ply Br. 23. But the cases Egenera cites do not compel its
favored outcome and do not endorse black-box claiming.
First, none of Egenera’s precedent considers Williamson.
See Media Rights Techs., Inc. v. Capital One Fin. Corp.,
800 F.3d 1366, 1373 (Fed. Cir. 2015) (cautioning against
relying on pre-Williamson precedent). Second, in those
cases the claim language and specification provided suffi-
cient structure to the “inputs, outputs, connections, and op-
eration” such that the pre-Williamson strong presumption
against means-plus-function claiming was not overcome.
E.g., Apple, 757 F.3d at 1303 (noting that because “the
claim language and specification outline the rules that the
[claim term] follow[s],” the written description places clear
structural limitations on the claim term and so the “patent
recites a claim term with a known meaning”). In contrast,
here the claims and specification provide no structural lim-
itation to the “inputs, outputs, connections, and operation”
of the claimed “logic to modify.”
We agree with Cisco: § 112(f) applies here. As used,
“logic” is no more than a “black box recitation of structure”
that is simply a generic substitute for “means.” See Wil-
liamson, 792 F.3d at 1350. We therefore conclude that
Cisco overcame the presumption against applying § 112(f).
B
Egenera next argues that the district court identified
the wrong structure as corresponding to the claimed func-
tions of the “logic to modify” limitation.
This limitation recites two functions: (1) “to modify said
received messages to transmit said modified messages to
the external communication network”; and (2) “to modify
said received messages to transmit said modified mes-
sages . . . to the external storage network.” See ’430 patent
claim 1 (emphases added).
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EGENERA, INC. v. CISCO SYSTEMS, INC. 13

The district court concluded that the structure corre-
sponding to the first function was “virtual LAN server 335,
virtual LAN proxy 340, and physical LAN driver 345” and
equivalents. Claim Construction Decision, 2018 WL
717342, at *7. The parties call this the “tripartite struc-
ture.”
Egenera now agues on appeal that the tripartite struc-
ture is too broad. Appellant’s Br. 55–59. Within the tri-
partite structure, insists Egenera, only the virtual LAN
proxy “modifies outgoing messages.” Id. at 59. Cisco disa-
grees, pointing to its expert’s testimony that the proxy does
not “act in isolation” and “cannot perform the recited func-
tion . . . by itself.” Appellee’s Br. 72 (citing J.A. 1431). Ra-
ther, the LAN proxy is merely “the middleman.” Id. at 73.
And, argues Cisco, Egenera cannot switch the scope of its
claim construction on appeal.
Egenera previously identified “control node 120” and
equivalents as the corresponding structure when it argued
at the district court. Claim Construction Decision,
2018 WL 717342, at *7. As Cisco highlights, this control
node is a broad structure that itself encompasses the tri-
partite structure. See Appellee’s Br. 70. Indeed, Egenera
argued below that the tripartite structure was
“overly[ ]narrow.” J.A. 3060.
Now Egenera contends that the structure it objected to
as overly narrow must be narrowed further. Egenera ex-
plains that, below, its proposed structure corresponded to
both claimed functions—i.e., not only messages to the “ex-
ternal communication network” but also messages to the
“external storage network.” Reply Br. at 24–26. We find
unpersuasive this explanation for Egenera’s switch in
scope, as Egenera fails to explain how subtracting the “ex-
ternal storage network” portions from the “control node”
leaves us with the ultra-narrow structure it advances
newly on appeal.
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14 EGENERA, INC. v. CISCO SYSTEMS, INC.

We agree with Cisco that Egenera cannot now seek a
much narrower construction on appeal. Digital-Vending
Servs. Int’l, LLC v. Univ. of Phoenix, Inc., 672 F.3d 1270,
1273 (Fed. Cir. 2012) (“[A] party may not, as a general rule,
change the scope of its claim construction on appeal.”). At
any rate, we also find the district court’s and Cisco’s rea-
soning persuasive on the merits. The components of the
tripartite structure—the virtual LAN server, virtual LAN
proxy, and physical LAN driver—function in concert to
modify messages to transmit to the external communica-
tions network. See Claim Construction Decision, 2018 WL
717342, at *7; ’430 patent col. 18 ll. 53–58, fig. 3B; Appel-
lee’s Br. 72–74.
Accordingly, we affirm the claim construction order.
II
Next we turn to Egenera’s contention that the district
court erred in applying judicial estoppel, thereby prevent-
ing correction of inventorship and invalidating its patent
as a consequence.
A
First, we address whether Egenera could correct inven-
torship, even absent judicial estoppel.
The Constitution authorizes awarding patent exclusiv-
ity only to an inventor. U.S. CONST. art. I, § 8, cl. 8. And
so courts have historically held that if a patent does not
reflect its true inventorship, it is invalid. See Pannu v.
Iolab Corp., 155 F.3d 1344, 1349–50 (Fed. Cir. 1998) (col-
lecting cases).
Inventorship is sometimes easy to determine. But
sometimes it is complicated, as with complex projects in-
volving many contributors at various times. Ultimately,
inventorship is a legal conclusion premised on underlying
factual findings, and one that depends on claim construc-
tion. In re VerHoef, 888 F.3d 1362, 1365 (Fed. Cir. 2018);
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EGENERA, INC. v. CISCO SYSTEMS, INC. 15

Trovan, Ltd. v. Sokymat SA, 299 F.3d 1292, 1302 (Fed. Cir.
2002). And like validity, inventorship is a claim-by-claim
question. Trovan, 299 F.3d at 1302. Accordingly, who
should be listed on the face of a patent may vary depending
on what, exactly, is claimed and what, exactly, a court de-
termines the claim scope to be.
The Patent Act allows a listing of inventors to be cor-
rected either upon petition to the Director, see 35 U.S.C.
§ 256(a), or upon court order, see § 256(b). Our precedent
recognizes that a patent cannot be invalidated if inventor-
ship can be corrected instead. Pannu, 155 F.3d at 1350.
The statutory text recognizes this too:
The error of omitting inventors or naming persons
who are not inventors shall not invalidate the pa-
tent in which such error occurred if it can be cor-
rected as provided in this section.
35 U.S.C. § 256(b) (emphases added). Section 256 applies
if “through error a person is named . . . as the inventor, or
through error an inventor is not named.” § 256(a).
As previously noted, the inventorship question in-
volved Egenera’s attempt to add back an inventor,
Mr. Schulter, who had previously been removed alongside
the IPR. The district court declared in a footnote that
Mr. Schulter’s removal by petition was therefore “a consid-
ered act that is unlikely to qualify as an omission ‘through
error.’” Judicial Estoppel Decision, 348 F. Supp. 3d
at 102 n.1. Cisco agrees, arguing that Egenera’s petition
was a “tactical ploy” rather than a “reasonable, but mis-
taken, effort to get inventorship right.” Appellee’s
Br. 27–30 (arguing that “error” requires a “good-faith mis-
take”). We note that although the district court declined to
credit Egenera’s witnesses’ accounts of conception, it also
declined to find inequitable conduct on these facts, despite
being urged by Cisco to do so. See Judicial Estoppel Deci-
sion, 348 F. Supp. 3d at 101; Invalidity Decision, 379 F.
Supp. 3d at 129.
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16 EGENERA, INC. v. CISCO SYSTEMS, INC.

Our precedent provides that “error” in § 256 includes
“all varieties of mistakes—honest and dishonest”—rather
than only unintentional inaccuracy. Stark v. Advanced
Magnetics, Inc., 119 F.3d 1551, 1554–56 (Fed. Cir. 1997). 3
That is, Stark expressly construed “error” to “embrace
more than simply honest mistakes.” Id. at 1554. Stark’s
broad interpretation was intended to “harmonize[] well
with the title 35 policy of seeking to reward the actual in-
ventors of technological advances.” Id. Indeed, § 256 is a
savings provision, functioning to prevent invalidation
when correction is available. It is the inequitable-conduct
rules that provide a safety valve in the event of deceit. Id.
at 1555–56.
Cisco invites us to sidestep Stark because the AIA has
since amended § 256. Previously, § 256 contained an addi-
tional requirement that the “error” of omitting an inventor
occurred without “deceptive intention” on the inventor’s
part. The scope of “error,” standing alone, was therefore

3 Reissue under 35 U.S.C. § 251 also requires “error,”
and our case law there is consistent with our case law on
§ 256. See, e.g., Fleming v. Escort Inc., 774 F.3d 1371, 1380
(Fed. Cir. 2014) (“Errors are not limited to slips of the pen
but encompass—and most often are—deliberate drafting
choices. Not all choices qualify . . . .” (citation omitted)); id.
(stating that error includes “deficient understandings” and
choices that rest on “cognizable false or deficient under-
standing of fact or law” but not simply a “now-regretted
choice”); In re Dinsmore, 757 F.3d 1343, 1347–48 (Fed. Cir.
2014); In re Rosuvastatin Calcium Pat. Litig., 703 F.3d 511,
522–24 (Fed. Cir. 2012) (applying pre-AIA language and
including deliberate actions) (collecting cases); In re Amos,
953 F.2d 613, 616 (Fed. Cir. 1991) (noting that error in-
cludes attorney’s mistake in understanding claim scope,
“one of the most common sources of defects” (quoting In re
Wilder, 736 F.2d 1516, 1519 (Fed. Cir. 1984)).
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EGENERA, INC. v. CISCO SYSTEMS, INC. 17

broad enough to otherwise include acts amounting to “de-
ceptive intention”—that is, intentional inaccuracy. See
Stark, 119 F.3d at 1554. With the AIA, “without . . . decep-
tive intention” was struck from that section. See AIA, Pub.
L. No. 112-29, § 20(f)(1)(B), 125 Stat. 284, 334 (2011). The
essence of Cisco’s position is that when Congress removed
this restrictive language that excluded intentional inaccu-
racy in certain cases, it somehow narrowed the meaning of
“error” to exclude intentional inaccuracy entirely. Appel-
lee’s Br. 30. Cisco argues that Congress’s removal of this
language was meant to harmonize “error” with what Cisco
views as its plain meaning—one that excludes intentional
inaccuracy. We had not yet addressed the impact of the
AIA on the holding of Stark. See, e.g., CODA Dev. S.R.O.
v. Goodyear Tire & Rubber Co., 916 F.3d 1350, 1358 n.6
(Fed. Cir. 2019). But we now reject Cisco’s proposed inter-
pretation because it is contrary to the text of § 256, the
structure of the AIA, 4 and the AIA’s legislative history. 5
We hold that the AIA did not narrow the meaning of

4 For instance, through the AIA, deceptive-intention
language was removed from the reissue provision,
35 U.S.C. § 251, as well as the analogue of § 256 that ap-
plies to patent applications, 35 U.S.C. § 116. See AIA
§ 20(a)(3)(B), (f)(1)(B), 125 Stat. at 333–34. The § 102(f)
improper-inventorship invalidity provision was also re-
moved. AIA § 3(b)(1), 125 Stat. at 285–86. And newly es-
tablished derivation proceedings provide for correction of
named inventors. AIA § 3(i), 125 Stat. at 289–90 (codified
at 35 U.S.C. § 135(b)).
5 See, e.g., 157 Cong. Rec. S1378 (daily ed. Mar. 8,
2011) (statement of Sen. Kyl) (“Eliminating the various de-
ceptive-intent requirements moves the U.S. patent system
away from the 19th century model that focused on the pa-
tent owner’s subjective intent, and towards a more objec-
tive-evidence-based system that will be much cheaper to
litigate and more efficient to administer.”).
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18 EGENERA, INC. v. CISCO SYSTEMS, INC.

“error.” Accordingly, § 256 does not exclude “considered
acts,” or even “deceptive intention,” from the meaning of
“error.” Cf. Judicial Estoppel Decision, 348 F. Supp. 3d at
102 n.1. “Error” is simply the incorrect listing of inventors.
Egenera asserted in its inventorship petition to the
PTO, concurrent with the IPR, that Mr. Schulter was in-
correctly listed as an inventor. At the time, no one had ar-
gued that “logic to modify” was a means-plus-function
term. Indeed, it presumptively was not. And Egenera op-
posed such a construction when Cisco later advanced it;
likewise, its position that Mr. Schulter was not an inventor
was seemingly consistent with its preferred construction.
But the court rejected Egenera’s construction in a way that
also illuminated Mr. Schulter’s necessary presence as an
inventor. After a three-day trial, and this appeal, the
claim-construction and inventorship questions have at last
been resolved. Because of these legal determinations, in
retrospect, Egenera’s assertion in its inventorship petition
was incorrect: Mr. Schulter was an inventor. According,
we conclude that Mr. Schulter’s omission was “error.”
B
Next we turn to judicial estoppel. 6 As noted, the dis-
trict court here concluded that Egenera was judicially es-
topped from adding Mr. Schulter’s name back to the patent
after it held a trial establishing him to be an inventor—
thereby invalidating the patent for improper inventorship.

6 Cisco contends that Egenera waived any argument
against judicial estoppel. Appellee’s Br. 31. Regardless,
whether to apply the waiver rule is discretionary. Here,
there has been complete briefing and argument on the ju-
dicial estoppel issue. See Automated Merch. Sys., Inc.
v. Lee, 782 F.3d 1376, 1379–80 (Fed. Cir. 2015). To apply
waiver would not serve judicial economy or promote fair-
ness, and so we address the merits.
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EGENERA, INC. v. CISCO SYSTEMS, INC. 19

As an initial matter, Egenera insists that judicial es-
toppel can never prevent § 256 from saving a patent’s va-
lidity. Appellant’s Br. 33–36; see Oral Arg. at 00:40–58,
No. 19-2015, http://oralarguments.cafc.uscourts.gov/de-
fault.aspx?fl=19-2015.mp3. We need not decide that issue,
however, because in this case the criteria for judicial estop-
pel were not met.
For questions of judicial estoppel, we apply the law of
the regional circuit—here the First Circuit. Akamai
Techs., Inc. v. Limelight Networks, Inc., 805 F.3d 1368,
1374 (Fed. Cir. 2015). The legal effect of representations
to the PTO and statutory interpretation of the Patent Act,
however, are issues of Federal Circuit law. See Endo
Pharm. Inc. v. Teva Pharm. USA, Inc., 919 F.3d 1347, 1352
(Fed. Cir. 2019). Under First Circuit law, we review a dis-
trict court’s application of judicial estoppel for abuse of dis-
cretion. Akamai, 805 F.3d at 1374 (citing Knowlton
v. Shaw, 704 F.3d 1, 9–10 (1st Cir. 2013)). We accept un-
derlying findings of fact unless they are clearly erroneous
and review the resolution of legal questions de novo. Id.
The First Circuit “treat[s] a material mistake of law as a
per se abuse of discretion.” Perry v. Blum, 629 F.3d 1, 8
(1st Cir. 2010).
Judicial estoppel is an equitable doctrine that prevents
a litigant from taking a litigation position inconsistent with
one successfully asserted in an earlier court proceeding.
See id. “The purpose of the doctrine is to protect the integ-
rity of the judicial process.” Id. Although the “contours of
judicial estoppel are hazy,” and its application is case-de-
pendent, the First Circuit applies the New Hampshire fac-
tors. RFF Family P’ship v. Ross, 814 F.3d 520, 527–28
(1st Cir. 2016) (Souter, J., sitting by designation). Accord-
ingly, a court examines (1) whether a party’s earlier and
later positions are “clearly inconsistent”—that is, “mutu-
ally exclusive”; (2) whether the party “succeeded in per-
suading a court to accept” the earlier position; and
(3) whether the party would “derive an unfair advantage or
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20 EGENERA, INC. v. CISCO SYSTEMS, INC.

impose an unfair detriment” on the other side if not es-
topped. New Hampshire v. Maine, 532 U.S. 742, 750–51
(2001).
We address the New Hampshire factors in turn.
1
First, Egenera advanced no “clearly inconsistent” posi-
tions.
To be “clearly inconsistent,” positions must be “mutu-
ally exclusive” and “directly inconsistent.” RFF, 814 F.3d
at 528 (quoting Alt. Sys. Concepts, Inc. v. Synopsys, Inc.,
374 F.3d 23, 33 (1st Cir. 2004)).
In its § 256(a) petition, Egenera asked the PTO as a
matter of formality “to delete Peter Schulter as an inventor
of the invention being claimed.” J.A. 9367; see also
37 C.F.R. § 1.324; MPEP § 1481.02 (9th ed. Rev 10.2019,
June 2020). Cisco argues that the “clearly inconsistent po-
sitions” were the two contrary uses of § 256. 7 See Oral Arg.
at 19:05–25, 26:29–38. Here, of course, in light of the dis-
trict court’s claim construction and accompanying inven-
torship determination, Egenera is asking the district court
to add Mr. Schulter back as an inventor. The district court
concluded that “Egenera’s suggestion that Schulter may be
relisted as an inventor as circumstances may dictate” was
clearly inconsistent with its “September 2017 petition . . .
that Schulter’s name was erroneously listed.” Judicial Es-
toppel Decision, 348 F. Supp. 3d at 102. This was incorrect.

7 If Cisco’s argument were accepted, it is hard to see
how any inventorship correction could occur under § 256.
By definition, a request to change inventorship would be
inconsistent with the “position” taken at the outset of pros-
ecution, in which inventor names are submitted with the
application. And serial petitions would be impossible.
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EGENERA, INC. v. CISCO SYSTEMS, INC. 21

We do not think that multiple corrections under § 256
are per se “mutually exclusive.” In any event, the district
court’s intervening claim-construction and inventorship
determinations further justify any seeming inconsistency.
Cf. Biomedical Pat. Mgmt. Corp. v. Cal. Dep’t of Health
Servs., 505 F.3d 1328, 1341–42 (Fed. Cir. 2007) (noting that
“inconsistency” in the judicial estoppel context “is excused
by an intervening change in the law”); see generally
18B Wright & Miller, Federal Practice & Procedure
§ 4477.3 (2d ed., Apr. 2020 update).
Inventorship, a complex legal conclusion, can depend
on claim construction. Here, the underlying presumption
was that Egenera’s claim terms, lacking “means,” were not
means-plus-function. Egenera’s inventorship petition was
consistent with that presumption. Indeed, it may well be
that Mr. Schulter would not be an inventor under Egen-
era’s preferred construction; but inventorship under that
claim construction was not decided. And Egenera consist-
ently protested the means-plus-function construction both
at the district court and on appeal—a construction that the
inventorship question was directly predicated on. There-
fore, once those issues were decided, it was entirely con-
sistent for Egenera to request an accompanying formal
correction of inventorship. Accordingly, at least due to the
intervening claim construction, it was not “mutually exclu-
sive,” as judicial estoppel requires, to again request formal
correction of inventorship.
The district court thus erred in discerning “clearly in-
consistent” positions.
2
Second, Egenera did not succeed in persuading a court
or court-like tribunal to accept its first position.
“‘Acceptance’ in this context is a term of art.” Perry,
629 F.3d at 11. That is, “a party need not show that the
earlier representation led to a favorable ruling on the
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22 EGENERA, INC. v. CISCO SYSTEMS, INC.

merits . . . but must show that the court adopted and relied
on the represented position either in a preliminary matter
or as part of a final disposition.” Id. And “[t]he showing of
judicial acceptance must be a strong one.” Id. In this fac-
tor, we ask whether the earlier tribunal’s acceptance impli-
cated the “truth-seeking function of the court.” Id. at 11
(quoting Teledyne Indus., Inc. v. NLRB, 911 F.2d 1214,
1218 (6th Cir. 1990)). This requirement aligns with the
doctrine’s purpose of “safeguard[ing] the integrity of the
courts by preventing parties from improperly manipulating
the machinery of the judicial system.” New Hampshire,
532 U.S. at 750.
The district court concluded that “[t]he PTO accepted
these representations”—referring to the inventorship peti-
tion. Judicial Estoppel Decision, 348 F. Supp. 3d at 102.
As an initial matter, the inventorship petition contained no
underlying statements of fact—simply statements that
Mr. Schulter’s listing was erroneous and that all the co-
listed inventors agreed or did not disagree. See J.A.
9367–80. The PTO did not cast these statements into the
crucible of examination. Rather, it agreed that all the sig-
natures and fees were in order. See J.A. 9388; MPEP
§ 1481.02.
Egenera contends that its statements in its petition
“did not involve the judicial process necessary for judicial
estoppel.” Appellant’s Br. 42. Instead, the § 256 petition
process is “ministerial” and “does not involve any tribunal,
judicial officer, or substantive analysis.” Id. Cisco replies
that Egenera undisputedly “persuaded” the PTO that
“Schulter was not an inventor.” Appellee’s Br. 44.
Under 37 C.F.R. § 1.324(b), the PTO examines a re-
quest only for the presence of supporting statements and
the required fee. See also MPEP § 1481.02; J.A. 9388. No
substantive examination occurs, and the PTO does not con-
sider the substantive adequacy of the petition. Cisco ar-
gues that the First Circuit has rejected a “ministerial”
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EGENERA, INC. v. CISCO SYSTEMS, INC. 23

exception. But in explanation, Cisco points out that unex-
amined identification of assets during bankruptcy proceed-
ings can ground judicial estoppel in a later bankruptcy
proceeding. See Appellee’s Br. 45 (citing Guay v. Burack,
677 F.3d 10, 17 (1st Cir. 2012)). We find Cisco’s arguments
unpersuasive: bankruptcy schedules occur in the context of
a bankruptcy court—they are specific representations of
fact before a tribunal. 8 And as Egenera argues, Cisco’s
chosen administrative judicial-estoppel precedents involve
“inconsistent statements about an objective fact, such as
the existence of bankruptcy assets or a claimed disability”
rather than “context-related legal conclusions.” Reply Br.
19. 9
Accordingly, even though we agree that judicial estop-
pel can occur in an administrative tribunal, 10 we disagree
that a § 256 petition, without more, counts as “persuasion”
of a “court” for judicial-estoppel purposes.

8 Cisco also points to out-of-circuit applications of ju-
dicial estoppel related to the Social Security Administra-
tion’s acceptance of statements in a disability-insurance
application. See Appellee’s Br. 46 n.3. Again, those cases
are not only not binding but also unpersuasive, as they in-
volve inconsistent statements about objective facts.
9 “[J]udicial estoppel arises only from a position
taken in an adjudicatory proceeding. Inconsistent positions
taken in other contexts must be measured by other theo-
ries.” Federal Practice & Procedure § 4477; see also id.
§ 4477.2 (“A position asserted before a government official
in nonadjudicatory proceedings . . . should not support ‘ju-
dicial’ estoppel.”).
10 See Trs. v. United States, 593 F.3d 1346, 1354 (Fed.
Cir. 2010) (“Judicial estoppel applies just as much when
one of the tribunals is an administrative agency as it does
when both tribunals are courts.” (emphasis added)).
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24 EGENERA, INC. v. CISCO SYSTEMS, INC.

This determination is narrow. We do not hold that ju-
dicial estoppel cannot apply to statements made during
substantive prosecution, ex parte reexamination, or other
quasi-adjudicatory proceedings—an issue not before us.
And we do not go so far as to say that other theories of es-
toppel cannot apply to ministerial filings or representa-
tions before the PTO. But judicial estoppel cannot be
stretched beyond persuading a tribunal, and it does not ap-
ply here.
3
Third, Egenera would gain no unfair advantage, and
Cisco would suffer no unfair prejudice, if judicial estoppel
were not applied.
The focus of this inquiry is on whether not applying es-
toppel would result in unfair advantage or prejudice. See
New Hampshire, 532 U.S. at 751 (“[Courts ask] whether
the party seeking to assert an inconsistent position would
derive an unfair advantage . . . if not estopped.”); RFF,
814 F.3d at 528.
Egenera argues that it would obtain no unfair ad-
vantage by correcting inventorship in conformance with
the district court’s inventorship determination. Appel-
lant’s Br. 45–46. The petition was not granted until after
the Board denied institution of the IPR on the merits.
Egenera points out that the petition did not affect the IPR,
and correction would simply “foster resolution of this case
on the merits.” Appellant’s Br. 45–46. Cisco responds that,
as the district court noted, Egenera’s disavowal of
Mr. Schulter’s inventorship enabled it to argue for an ear-
lier priority date to bolster its IPR and litigation position.
Appellee’s Br. 47; Judicial Estoppel Decision, 348 F.
Supp. 3d at 101–02. But in any event, it ended up not mak-
ing a difference. The Board considered Cisco’s prior art
without addressing Egenera’s priority arguments. And
Cisco fails to explain how, even if there would be an
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EGENERA, INC. v. CISCO SYSTEMS, INC. 25

advantage conferred on Egenera by failure to estop, that
advantage would be “unfair” under these facts.
Things might be different had Egenera succeeded in
swearing behind the prior art. We do not go so far as to
declare that there would be no potential for judicial estop-
pel had the Board fully considered and adopted Egenera’s
swearing-behind arguments. But that would be estoppel
on the basis of a prior representation to a tribunal (i.e., the
Board). And both prejudice and inconsistency would be
clear: there would be the potential of two judicial decisions
predicated on opposite inventorship statuses. But that is
not this case. Here, there would be no unfair prejudice in
refusing to estop. The district court did not identify any.
See Judicial Estoppel Decision, 348 F. Supp. 3d at 101–02.
Cisco identified none in its brief, nor when pressed at oral
argument. See Oral Arg. at 15:30–17:34.
Cisco dismisses this prong of the New Hampshire fac-
tors as purely optional under First Circuit law, arguing
only that it is “enough that Egenera took ‘contradictory’ po-
sitions ‘in search of legal advantage.’” Appellee’s Br. 47,
49–50 (citing Alt. Sys. Concepts, 374 F.3d at 33). We disa-
gree with Cisco’s reading of Alternative System Concepts,
which would collapse the first and third prongs into one.
And we decline to ignore abundant First Circuit precedent
signifying the importance of this factor. E.g., RFF,
814 F.3d at 528; Perry, 629 F.3d at 8–9.
Accordingly, there would be no unfair advantage or un-
fair prejudice in refusing to estop Egenera.
4
The district court legally erred as to each New Hamp-
shire factor. We therefore hold that the district court
abused its discretion by applying judicial estoppel.
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26 EGENERA, INC. v. CISCO SYSTEMS, INC.

CONCLUSION
We have considered the parties’ remaining arguments
but find them unpersuasive. For the foregoing reasons, we
affirm the district court’s claim construction but vacate the
district court’s invalidity judgment and the accompanying
cost award. We remand for further proceedings.
AFFIRMED-IN-PART, VACATED-IN-PART, AND
REMANDED
COSTS
The parties shall bear their own costs.