Opinion for the court filed by Circuit Judge LOURIE. Concurring-in-part and dissenting-in-part opinion filed by Circuit Judge PLAGER.
LOURIE, Circuit Judge.
Nobelpharma AB and Nobelpharma USA, Inc. (collectively, NP) appeal from the judgment of the United States District Court for the Northern District of Illinois holding that (1) U.S. Patent 4,330,891 is invalid under 35 U.S.C. § 112, ¶ 1 (1994), for failure to disclose the best mode of carrying out the invention, (2) Implant Innovations, Inc. (31) did not infringe the ’891 patent, and (3) NP was not entitled to JMOL or, in the alternative, a new trial following the jury verdict in favor of 31 on its antitrust counterclaim against NP, Dr. Per-Ingvar Branemark, and the Institute for Applied Biotechnology. See Nobelpharma AB v. Implant Innovations, Inc., 930 F.Supp. 1241 (N.D.Ill.1996). We conclude that the district court did not err in granting judgment that the patent is invalid as a matter of law at the close of NP’s ease-in-chief, but that it did err in denying NP’s motion for JMOL on the antitrust counterclaim. Accordingly, the decision of the district court is affirmed-in-part and reversed-in-part.
BACKGROUND
Drs. Branemark and Bo-Thuresson af Ek-enstam are the named inventors on the ’891 patent, the application for which was filed in 1980 and claimed priority from a Swedish patent application that was filed in 1979. The patent claims “an element intended for implantation into bone tissue.” This “element,” when used as part of a dental implant, is placed directly into the jawbone where it acts as a tooth root substitute. The implants described and claimed in the patent are preferably made of titanium and have a network of particularly-sized and particularly-spaced “micropits.” These micropits, which have diameters in the range of about 10 to 1000 nanometers or, preferably, 10 to 300 nanometers, allow a secure connection to form between the implant and growing bone tissue through a process called “osseointegration.”
Branemark is also one of the authors of a book published in 1977, entitled “Osseointe-grated Implants in the Treatment of the Edentulous Jaw Experienced from a 10-Year Period” (hereinafter “the 1977 Book”). As its title suggests, this book describes a decade-long clinical evaluation of patients who had received dental implants. The 1977 Book includes a single page containing four scanning electron micrographs (SEMs) of titanium implants that exhibit micropits. The caption describing these SEMs reads, in part: “Irregularities are produced during manufacturing in order to increase the retention of the implants within the mineralized tissue.” 31 determined, based on measurements and calculations that it presented to the trial court, that the micropits shown in the 1977 Book have diameters within the range claimed in the ’891 patent. However, the 1977 Book does not specifically refer to “mieropits.”
In preparing to file the Swedish patent application, af Ekenstam submitted a draft written description of the invention to the inventors’ Swedish patent agent, Mr. Bar-nieske. This draft referred to the 1977 Book in the following translated passage:
In ten years of material pertaining to titanium jaw implants in man, Branemark et al. [in the 1977 Book] have shown that a very high frequency of healing, as stated above, can be achieved by utilizing a carefully developed surgical technique and adequately produced implants.
However, Barnieske deleted all reference to the 1977 Book from the patent application that was ultimately filed in Sweden. Similarly, the 1977 Book is not mentioned in the [1466]*1466U.S. patent application filed by Barnieske on behalf of Branemark and af Ekenstam.
In June 1980, while the U.S. patent application was pending, Branemark entered into an exclusive license agreement with NP covering the claimed technology.1 Barnieske kept NP informed of the prosecution of the U.S. patent application and received assistance from NP’s U.S. patent agent. The ’891 patent issued in 1982; NP has since asserted it in at least three patent infringement suits.
In July 1991, while Branemark was a member of NP’s Board of Directors, NP brought this suit alleging that certain of 3I’s dental implants infringed the ’891 patent. 31 defended on the grounds of invalidity, unem forceability, and non-infringement. 31 also brought an antitrust counterclaim, based in part on the assertion that NP attempted to enforce a patent that it knew was invalid and unenforceable. Specifically, 31 alleged that when NP brought suit, NP was aware that the inventors’ intentional failure to disclose the 1977 Book to the U.S. Patent and Trademark Office (PTO) would render the ’891 patent unenforceable.
During its case-in-chief, NP introduced portions of a deposition of Branemark that apparently was conducted several years before this trial began in connection with a lawsuit involving neither NP nor 31. NP also introduced into evidence portions of that deposition that were counter-designated for introduction by 31. Branemark’s deposition testimony included his admissions that one “could consider” the procedure used to manufacture the micropitted surface a trade secret, and “it might be” that there are details “important to making” the micropitted surface that are not disclosed in the patent. At the close of NP’s case-in-chief, the district court granted 3I’s motion for JMOL of invalidity and non-infringement. The court held that the patent was invalid under § 112, ¶ 1, for failure to disclose the best mode and that NP had failed to prove infringement. The court then denied NP’s motion for JMOL on 3I’s antitrust counterclaim, proceeded to inform the jury that the court had held the patent invalid, and allowed 31 to present the counterclaim to the jury.
After trial limited to the antitrust issue, the jury found in special verdicts, inter alia, that 31 had proven that (1) “the inventors or their agents or attorneys obtained the ’891 patent through fraud,” (2) NP “had knowledge that the ’891 patent was obtained by fraud at the time this action was commenced against 31,” and (3) NP “brought this lawsuit against 31 knowing that the ’891 patent was eithér invalid or unenforceable and with the intent of interfering directly with 3I’s ability to compete in the relevant market.” The jury awarded 31 approximately $3.3 million in compensatory damages, an amount the court trebled pursuant to section 4 of the Clayton Act, 15 U.S.C. § 15 (1994). The court declined to rule on whether the patent was unenforceable for inequitable conduct, concluding that its judgment of invalidity rendered the issue of enforceability moot. Nobelpharma AB v. Implant Innovations, Inc., 875 F.Supp. 481, 34 USPQ2d 1090 (N.D.Ill.1995).
The court then denied NP’s renewed motion for JMOL on the counterclaim or, in the alternative, for a new trial on both the counterclaim and the infringement claim. Nobelpharma AB, 930 F.Supp. at 1246. In denying NP’s post-verdict motion for a new trial on the issue of infringement, the district court again concluded that the patent was invalid for failure to disclose the best mode. Id. at 1247-49. The court also concluded that NP was not entitled to JMOL on the counterclaim because, inter alia, “NP, as the assignee of the patent, maintained and enforced the patent with knowledge of the patent’s fraudulent derivation.” Id. at 1257. The court denied NP’s motion for a new trial on the counterclaim, holding, inter alia, that it did not err in its evidentiary rulings or in refusing to instruct the jury that in order to impose antitrust liability against NP, it must find NP’s lawsuit “objectively baseless.” Id. at 1264.
NP appealed to this court, challenging the district court’s grant of 3I’s motion for [1467]*1467JMOL of invalidity and non-infringement and its denial of the post-verdict motion for JMOL or a new trial. We have jurisdiction pursuant to 28 U.S.C. § 1295(a)(1) (1994).
DISCUSSION
A. Invalidity
At the close of NP’s case-in-chief, the district court granted 3I’s motion for judgment of invalidity under § 112, ¶ 1, as a matter of law for failure to disclose the best mode of practicing the invention. NP then filed a motion for reconsideration, which was denied, in order to reopen the evidence and offer proof regarding its compliance with § 112, ¶ 1. After the jury returned its verdict in favor of 31 on its antitrust counterclaim, NP moved for a new trial, again arguing that the court had erred in granting 3I’s motion for JMOL. In reaffirming its decision to grant 3I’s motion for JMOL, the district court held that Branemark’s own testimony “demonstrates that when [he] filed his patent application, he contemplated a best mode of practicing his invention, but his disclosures were inadequate to enable one skilled in the art to practice that best mode.” 930 F.Supp. at 1248. The district court also explicitly noted that its decision was not based on Branemark’s purported “non-disclosure” of NP’s later-developed manufacturing procedure. Id.
On appeal, NP again argues that the district court erred in granting JMOL on the invalidity issue because in doing so the court drew improper, unsupported inferences against NP and erroneously imposed on NP the burden of proving validity. NP also argues that the grant of JMOL denied it due process because the court had mandated a “natural order of proof’ at trial and thus had effectively barred NP from introducing any evidence to show that it had satisfied the best mode requirement during its case-in-chief.
In response, 31 argues that Branemark’s own unequivocal admissions indicate that he had developed and tested a preferred method of making the claimed implants when the patent application was filed. 31 also argues that Branemark admitted that the patent does not contain a disclosure adequate to enable one of ordinary skill in the art to practice this method. Finally, 31 argues that NP was not denied due process because NP had sufficient opportunity to offer evidence in opposition to 3I’s motion for JMOL of invalidity and failed to do so. We agree with 31 that the court did not err in its grant of the motion for JMOL and therefore that the court did not err in denying NP’s motion for a new. trial on its infringement claim.
We review a district court’s grant of a motion for JMOL under Fed.R.Civ.P. 50(a)(1) de novo by reapplying the standard applicable at the district court. See Allied Colloids Inc. v. American Cyanamid Co., 64 F.3d 1570, 1573, 35 USPQ2d 1840, 1841 (Fed.Cir.1995). Under that standard, we examine the record in the light most favorable to the non-movant, which in this case is NP, and afford it the benefit of all reasonable inferences. Id. Accordingly, “[w]e may affirm only if the judgment entered was the only one possible under the controlling law.” Burroughs Wellcome Co. v. Barr Lab., Inc., 40 F.3d 1223, 1227, 32 USPQ2d 1915, 1919 (Fed.Cir.1994), cert. denied, — U.S. —, 116 S.Ct. 771, 133 L.Ed.2d 724 (1996) (citing Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 250, 106 S.Ct. 2505, 2511, 91 L.Ed.2d 202 (1986) (prohibiting JMOL “[i]f reasonable minds could differ as to the import of the evidence.”)).
Rule 50(a)(1) provides, in relevant part, that if
a party has been fully heard on an issue and there is no legally sufficient evidentia-ry basis for a reasonable jury to find for that party on that issue, the court may determine the issue against that party and may grant a motion for judgment as a matter of law [JMOL] against that party with respect to a claim or defense that cannot under the controlling law be maintained or defeated without a favorable finding on that issue.
Fed.R.Civ.P. 50(a). “Thu's, the verdict may be directed after the plaintiffs case is presented, when it is clear that completion of the trial is unnecessary in that the only sustainable verdict could be in favor of the defen[1468]*1468dant.” Allied Colloids, 64 F.3d at 1573, 35 USPQ2d at 1841.
By statute, patents are presumed to be valid. 35 U.S.C. § 282 (1994). Thus, 31 had the burden of establishing by clear and convincing evidence facts supporting the conclusion that the ’891 patent is invalid. See Transco Prods. Inc. v. Performance Contracting, Inc., 38 F.3d 551, 560, 32 USPQ2d 1077, 1084 (Fed.Cir.1994), cert. denied, 513 U.S. 1151, 115 S.Ct. 1102, 130 L.Ed.2d 1069 (1995). The patent statute requires that a patent specification “shall set forth the best mode contemplated by the inventor of carrying out his invention.” 35 U.S.C. § 112, ¶ 1 (1994). Determining whether a patent fails to comply with the best mode requirement and is thus invalid involves two factual inquiries. First, the fact-finder must determine whether at the time an applicant filed an application for patent, he or she had a best mode of practicing the invention, which is a subjective determination. Second, if the inventor had a best mode of practicing the invention, the fact-finder must determine whether the best mode was disclosed in sufficient detail to allow a skilled artisan to practice it without undue experimentation, which is an objective determination. See United States Gypsum Co. v. National Gypsum Co., 74 F.3d 1209, 1212, 37 USPQ2d 1388, 1390 (Fed.Cir.1996).
For whatever reason, NP introduced as part of its own case-in-chief all of the portions of Branemark’s deposition that were counter-designated by 3I.2 These included Branemark’s statements, introduced by and unchallenged by NP, that (1) “there were some minor details that were not included [in the patent] and which proved to be quite important,” (2) other skilled artisans would have to be “lucky” to obtain a suitable micro-pitted implant “by cutting a piece of titanium at a speed less than twenty meters per minute,” the cutting speed disclosed in the patent, and (3) “any of the small detailed recipes that I discussed but did not specify” in the patent “can cause you to fail to get micropit-ting even though you were cutting the metal at less than twenty meters per minute.” The record also unambiguously indicates that when he filed his patent application, Brane-mark was aware that a variety of undisclosed machining parameters were critical to the production of a functional implant, ie., one that would allow for osseointegration. Moreover, the research on which the 1977 Book was based also indicates that Branemark possessed a preferred mode of making the claimed implants by the time the U.S. patent application was filed in 1980. Thus, the evidence at trial leads to only one reasonable conclusion: Branemark possessed a preferred method of making the claimed invention and failed to disclose it sufficiently to enable those skilled in the art to practice that method.
Normally, evidence presented by a patentee-plaintiff will not support a grant of a JMOL invalidating a patent. That is because the burden is on an accused infringer to show by clear and convincing evidence facts supporting the conclusion that the patent is invalid. See generally 9A Charles Alan Wright & Arthur R. Miller, Federal Practice and Procedure, § 2535, at 325 (2d ed. 1994) (“[C]ourts often caution that granting a [JMOL] for the party bearing the burden of proof is reserved for extreme cases.”). Accordingly, grant of JMOL in favor of a party bearing the burden of proof may be granted only where (1) the movant “has established [its] case by evidence that the jury would not be at liberty to disbelieve” and (2) “the only reasonable conclusion is in [the movant’s] favor.” Hurd v. American Hoist & Derrick Co., 734 F.2d 495, 499 (10th Cir.1984). However, in unusual cases, an admission made by a plaintiff’s witness can be sufficient to support entry of a JMOL in favor of a defendant after the close of the plaintiff’s case-in-chief, even where the defendant bears the burden of proof on the decided issue. See, e.g., Falco Lime, Inc. v. Tide Towing Co., 29 F.3d 362, 365-66 (8th Cir.1994) (holding that JMOL was properly granted after the close of plaintiff’s case in [1469]*1469view of the admissions of plaintiffs chief witness regarding a contract that established defendant’s affirmative defense). Given Branemark’s admissions, we conclude that this is one of those “extreme” cases in which it was not improper to grant JMOL in favor of a defendant on an issue regarding which it bore the burden of proof.
Contrary to NP’s arguments, the district court did not draw adverse inferences against NP to support its judgment. Rather, it properly relied on a co-inventor’s statements “that the jury would not be at liberty to disbelieve.” Hurd, 734 F.2d at 499. Similarly, the district court did not place the burden of proving validity on NP. The court did not have to shift the burden of proof because NP’s own evidence was clear and convincing that the patent is invalid. This evidence led to “the only reasonable conclusion.” Id.
We also agree with 31 that NP was not denied due process. When NP was confronted with 3I’s motion for JMOL, it was not unfairly surprised. 31 had consistently alleged that the ’891 patent was invalid under § 112, ¶ 1. Moreover, NP had an opportunity to oppose 3I’s motion, but it failed to do so adequately. After the court’s grant of JMOL, NP responded by offering evidence and argument only concerning NP’s later-developed manufacturing procedure. However, as noted above, the district court’s ultimate decision did not rely on the “non-disclosure” of NP’s later-developed manufacturing processes. Likewise, in affirming the decision of the district court, we do not rely on that evidence. Rather, we rely only on the clear and convincing evidence that Branemark failed to disclose his best mode of practicing the claimed invention when he filed his patent application. NP failed to present any evidence or argument to undermine the import of that evidence, even though it knew that the best mode issue was before the court; it thus had ample opportunity to prepare and present evidence and argument. Whatever disadvantage NP may have suffered when the JMOL was granted was rectified by the opportunity it had after the judgment was rendered. Any error was thus harmless. NP was therefore not denied due process.
Accordingly, we affirm the judgment that the ’891 patent is invalid as a matter of law under § 112, HI, for failure to disclose the best mode of practicing the invention. Because we affirm the district court’s decision holding the patent invalid, we need not consider NP’s arguments concerning infringement. See B.F. Goodrich Co. v. Aircraft Braking Sys. Corp., 72 F.3d 1577, 1583, 37 USPQ2d 1314, 1319 (Fed.Cir.1996).
B. Antitrust Counterclaim
After the jury returned its verdict in favor of 31 on its counterclaim that NP violated the antitrust laws by bringing suit against 31, the court denied NP’s motion for JMOL or, in the alternative, for a new trial under Fed. R.Civ.P. 50(b). In denying NP’s motion, the district court held that the verdict was supported, inter alia, by the jury’s factual findings that the patent was obtained through “NP’s knowing fraud upon, or intentional misrepresentations to, the [PTO]” and that “NP maintained and enforced the patent with knowledge of the patent’s fraudulent derivation” and with the intent of interfering directly with 3I’s ability to compete in .the relevant market. 930 F.Supp. at 1257. The court further held, based on these findings, that the jury need not have considered whether NP’s suit was “objectively baseless.” Id. at 1264.
In support of its position that the court erred in denying its renewed motion for JMOL, NP argues that there was a lack of substantial evidence to support the jury’s finding that the patent was obtained through “fraud” and its finding that NP was aware of that conduct when it brought suit against 31. NP also argues that these findings, even if supported by substantial evidence, do not provide a legal basis for the imposition of antitrust liability. Finally, NP argues that it is entitled to a new trial because the court failed to instruct the jury that bringing a lawsuit cannot be the basis for antitrust liability if that suit is not “objectively baseless.”
31 responds that the jury’s explicit findings that the patent was procured through fraudulent conduct and that NP knew of that [1470]*1470conduct when it brought suit were supported by substantial evidence, and that these findings provide a sound basis for imposing antitrust liability on NP. Responding to NP’s arguments for a new trial, 31 argues that an “objectively reasonable” or “objectively baseless” jury instruction was not necessary because the district court required that 31 prove that NP had actual knowledge of the inequitable conduct when it brought suit and that even if such an instruction was necessary, NP waived this argument by failing to propose a jury instruction relating to an “objectively baseless” standard.
We agree with NP that the court erred in denying its motion for JMOL; therefore we need not directly address the arguments concerning NP’s motion for a new trial. We review a district court’s denial of a post-trial motion for JMOL under Fed. R.Civ.P. 50(b) de novo by reapplying the standard applicable at the district court. Thus, this court
must determine whether there exists evidence of record upon which a jury might properly have returned a verdict in [the non-movant’s] favor when the correct legal standard is applied. If there is not, [the movant] was entitled to have the question removed from the jury and decided as a matter of law.
Markman v. Westview Instruments, Inc., 52 F.3d 967, 975, 34 USPQ2d 1321, 1326 (Fed.Cir.1995) (in banc), aff'd, — U.S. —, 116 S.Ct. 1384, 134 L.Ed.2d 577, 38 USPQ2d 1461 (1996) (quoting Jamesbury Corp. v. Litton Indus. Prods., Inc., 756 F.2d 1556, 1560, 225 USPQ 253, 257 (Fed.Cir.1985)); see also Deimer v. Cincinnati Sub-Zero Prods., Inc., 58 F.3d 341, 343 (7th Cir.1995); Shearing v. Iolab Corp., 975 F.2d 1541, 1544, 24 USPQ2d 1133, 1136 (Fed.Cir.1992) (“On appeal after denial of a motion for JNOV, the appellant must prove that the record lacks substantial evidence to support the jury’s verdict.”). In applying this standard, we must also “view the evidence in the light most favorable to the nonmoving party,” which in this case is 31. Deimer, 58 F.3d at 343.
When reviewing a district court’s judgment involving federal antitrust law, we apply the law of the regional circuit in which that district court sits. See Loctite Corp. v. Ultraseal, 781 F.2d 861, 875, 228 USPQ 90, 99 (Fed.Cir.1985) (‘We must approach a federal antitrust claim as would a court of appeal in the circuit of the district court whose judgment we review.”). Accordingly, we would apply Seventh Circuit antitrust law were it clear. However, since the Seventh Circuit has not clarified the conditions under which a patentee may incur antitrust liability for enforcing its patent, we must also turn to Supreme Court precedent and to the law of the other regional circuits to determine how the Seventh Circuit would likely decide this issue.
A patentee who brings an infringement suit may be subject to antitrust liability for the anti-competitive effects of that suit if the alleged infringer (the antitrust plaintiff) proves (1) that the asserted patent was obtained through knowing and willful fraud within the meaning of Walker Process Equipment, Inc. v. Food Machinery & Chemical Corp., 382 U.S. 172, 177, 86 S.Ct. 347, 350, 147 USPQ 404, 407 (1965), or (2) that the infringement suit was “a mere sham to cover what is actually nothing more than an attempt to interfere directly with the business relationships of a competitor,” Eastern R.R. Presidents Conference v. Noerr Motor Freight, Inc., 365 U.S. 127, 144, 81 S.Ct. 523, 533, 5 L.Ed.2d 464 (1961); California Motor Transp. Co. v. Trucking Unlimited, 404 U.S. 508, 510, 92 S.Ct. 609, 611-12, 30 L.Ed.2d 642 (1972) (holding that Noerr “governs the approach of citizens or groups of them ... to courts, the third branch of Government”). See Professional Real Estate Investors, Inc. v. Columbia Pictures Indus., Inc., 508 U.S. 49, 61 n. 6, 113 S.Ct. 1920, 1929 n. 6, 123 L.Ed.2d 611 (1993) (PRE) (declining to decide “whether and, if so, to what extent Noerr permits the imposition of antitrust liability for a litigant’s fraud or other misrepresentations”).
In Walker Process, the Supreme Court held that in order “to strip [the patentee] of its exemption from the antitrust laws” when attempting to enforce its patent monopoly, an antitrust plaintiff is required to prove that the patentee “obtained the patent by know[1471]*1471ingly and willfully misrepresenting facts3 to the [PTO].” 382 U.S. at 177, 86 S.Ct. at 350, 147 USPQ at 407. The Court also cited two of its prior decisions which involved knowing and willful misrepresentation of facts to the Patent Office, which the Court described as “fraudulent procurement”: Precision Instrument Manufacturing v. Automotive Maintenance Machinery Co., 324 U.S. 806, 65 S.Ct. 993, 89 L.Ed. 1381, 65 USPQ 133, 138 (1945), and Hazel-Atlas Glass Co. v. Hartford-Empire Co., 322 U.S. 238, 64 S.Ct. 997, 88 L.Ed. 1250, 61 USPQ 241 (1944).4 In Precision Instrument, the patentee submitted false dates of conception and reduction to practice, and fabricated evidence in support of these dates, to ensure priority in an interference proceeding. Similarly, in Hartford-Empire, the patentee’s attorney ensured that a patent would issue by falsely stating that an article he had authored praising the invention was actually written by a well-known expert in the field.
Justice Harlan, in a concurring opinion, emphasized that to “aehiev[e] a suitable accommodation in this area between the differing policies of the patent and antitrust laws,” a distinction must be maintained between patents procured by “deliberate fraud” and those rendered invalid or unenforceable for other reasons. Walker Process, 382 U.S. at 179-80, 86 S.Ct. at 351-52, 15 L.Ed.2d 247, 147 USPQ at 408. He then stated:
[T]o hold, as we do not, that private antitrust suits might also reach monopolies practiced under patents that for one reason or another may turn out to be voidable under one or more of the numerous technicalities attending the issuance of a patent, might well chill the disclosure of inventions through the obtaining of a patent because of fear of the vexations or punitive consequences of treble-damage suits. Hence, this private antitrust remedy should not be deemed available to reach [Sherman Act] § 2 monopolies carried on under a non-fraudulently procured patent.
Id. at 180, 86 S.Ct. at 351, 147 USPQ at 408.
The district court observed that the Supreme Court, in footnote six of its PRE opinion, “left unresolved the issue of how ‘Noerr applies to the ex parte application process,’ and in particular, how it applies to the Walker Process claim.” 930 F.Supp. at 1253 (quoting James B. Kobak, Jr., Professional Real Estate Investors and the Future of Patent-Antitrust Litigation, 63 Antitrust L.J. 185, 186 (1994)). The court also accurately pointed out that we have twice declined to resolve this issue. See FilmTec Corp. v. Hydranautics, 67 F.3d 931, 939 n. 2, 36. USPQ2d 1410, 1415 n. 2 (Fed.Cir.1995), cert. denied, — U.S. —, 117 S.Ct. 62, 136 L.Ed.2d 24 (1996); Carroll Touch, Inc. v. Electro Mechanical Sys., Inc., 15 F.3d 1573, 1583 n. 10, 27 USPQ2d 1836, 1845 n. 10 (Fed.Cir.1993). Therefore, after reviewing three opinions from the Ninth and District of Columbia Circuit Courts of Appeals, see Hydranautics v. FilmTec Corp., 70 F.3d 533, 537-38, 36 USPQ2d 1773, 1777 (9th Cir.1995); Whelan v. Abell, 48 F.3d 1247, 1255 (D.C.Cir.1995); Liberty Lake Invs., Inc. v. Magnuson, 12 F.3d 155, 158-60 (9th Cir.1993), the district court made its own determination that PRE’s two-part test for a sham is inapplicable to an antitrust claim based on the assertion of a patent obtained by knowing and willful fraud. 930 F.Supp. at 1253. We do not agree with that determination. PRE and Walker Process provide alternative legal grounds on which a patentee may be stripped of its immunity from the antitrust laws; both legal theories may be applied to the same conduct. Moreover, we need not find a way to merge these decisions. Each provides its [1472]*1472own basis for depriving a patent owner of immunity from the antitrust laws. The Supreme Court saw no need to merge these separate lines of cases and neither do we.
If the elements for a finding of fraud within the meaning of Walker Process, as well as the other criteria for antitrust liability, are met, such liability can be imposed without an additional sham inquiry. Alternatively, when an antitrust claim is based on a PRE allegation that a suit is baseless, in order to prove that a suit is within Noerr’s “sham” exception to immunity, an antitrust plaintiff must prove that the suit was both objectively baseless and subjectively motivated by a desire to impose collateral, anti-competitive injury rather to obtain a justifiable legal remedy. PRE, 508 U.S. at 60-61, 113 S.Ct. at 1928-29. As the Supreme Court stated:
First, the lawsuit must be objectively baseless in the sense that no reasonable litigant could realistically expect success on the merits. If an objective litigant could conclude that the suit is reasonably calculated to elicit a favorable outcome, the suit is immunized under Noerr, and the antitrust claim premised on the sham exception must fail. Only if the challenged litigation is objectively meritless may a court examine the litigant’s subjective motivation. Under the second part of our definition of sham, the court should focus on whether the baseless lawsuit conceals “an attempt to interfere directly with the business relationships of a competitor,” through the “use [of] the governmental process-as opposed to the outcome of that process-as an anticompetitive weapon.” ... Of course, even a plaintiff who defeats the defendant’s claim to Noerr immunity by demonstrating both the objective and the subjective components of a sham must still prove a substantive antitrust violation. Proof of a sham merely deprives the defendant of immunity; it does not relieve the plaintiff of the obligation to establish all other elements of his claim.
Id. (footnotes and internal citations omitted). Thus, under PRE, a sham suit is one that is both objectively baseless and subjectively brought in bad faith. If a suit is not objectively baseless, an antitrust defendant’s subjective motivation is immaterial. Id.
We conclude that 31 has proven no set of facts upon which a fact finder could strip NP of its immunity from antitrust liability. First, there exists no evidence to support the jury’s finding that the “patent was obtained by fraud” within the meaning of a Walker Process counterclaim. Walker Process requires a showing that the patent was obtained through deliberate, affirmative misrepresentations, ie., knowingly false statements, not mere omissions. See, e.g., Potters Med. Ctr. v. City Hospital Assoc., 800 F.2d 568, 581 (6th Cir.1986) (stating that “[o]nly known falsity supports an antitrust offense” and relying on an uncontested affidavit “which attested that [the antitrust defendant] knowingly made no false statements.’’) (emphasis added); Clipper Exxpress v. Rocky Mountain Motor Tariff Bureau, Inc., 690 F.2d 1240, 1261 (9th Cir.1982) (holding that under Walker Process “the fraudulent furnishing of false information to an agency in connection with the adjudicatory proceeding can be the basis for antitrust liability, if the requisite predatory intent is present and the other elements of an antitrust claim are proven.”) (emphasis added); Kearney & Trecker, Corp. v. Giddings & Lewis, Inc., 452 F.2d 579, 594, 171 USPQ 650, 662 (7th Cir.1971) (characterizing the conduct at issue in Walker Process as “fraud involving the willful misrepresentation of facts to the Patent Office.”); Bendix Corp. v. Balax, Inc., 421 F.2d 809, 819, 164 USPQ 485, 493 (7th Cir.1970) (“Thus, to prevail here, defendants must prove ... that any misstatements by plaintiff in its patent applications were the product of intentional fraud and not good faith mistake.”) (emphasis added). The jury’s verdict was based in part on its finding of “fraud,” but there exists no evidence of any affirmative misrepresentation that would constitute such fraud. Pursuant to then-existing PTO regulations, Branemark was required to aver, inter alia, that “the invention has not been ... described in any printed publication in any country before his invention or more than one year prior to his' application.” 37 C.F.R. § 1.65 (1990). The evidence does not support a finding that this [1473]*1473statement, or any other statement to the PTO made by or attributable to Branemark, was knowingly false. For, even if we accept 3I’s and the dissent’s unsupported assertion that Barnieske knew that the 1977 Book was material, knowledge that a reference is material is not the same as knowledge that a reference describes an invention and hence renders it unpatentable.
While there may have been substantial evidence to support a finding of inequitable conduct consisting of withholding the 1977 Book with the intent to deceive the PTO,5 under Walker Process such evidence will not support antitrust liability. As we have previously stated, inequitable conduct that will render a patent unenforceable is a broader, more inclusive concept than the “fraud” needed to support a Walker Process counterclaim. See, e.g., Hewlett-Packard Co. v. Bausch & Lomb Inc., 882 F.2d 1556, 1563, 11 USPQ2d 1750, 1756 (Fed.Cir.1989); FMC Corp. v. Manitowoc Co., 835 F.2d 1411, 1417-18, 5 USPQ2d 1112, 1117 (Fed.Cir.1987); Argus Chem. Corp. v. Fibre Glass-Evercoat Co., 812 F.2d 1381, 1384-85, 1 USPQ2d 1971, 1973-74 (Fed.Cir.1987); J.P. Stevens & Co. v. Lex Tex Ltd., 747 F.2d 1553, 1559, 223 USPQ 1089, 1092 (Fed.Cir.1984) (“Conduct before the PTO that may render a patent unenforceable is broader than common law fraud.”). Thus, inequitable conduct can include both an intentional failure to disclose material prior art as well as an intentional misrepresentation. See 37 C.F.R. § 1.56 (1996) (“Duty to disclose information material to patentability”); see also Kingsdown Med. Consultants Ltd. v. Hollister Inc., 863 F.2d 867, 872, 9 USPQ2d 1384, 1389 (Fed.Cir.1988). However, as noted above, only affirmative misrepresentations come within the definition of Walker Process fraud. See Potters Med. Ctr., 800 F.2d at 581; see also Argus Chem. Corp., 812 F.2d at 1384-85, 1 USPQ2d at 1973-74 (stating that “ ‘knowing and willful fraud,’ as the term is used in Walker, can mean no less than clear, convincing proof of intentional fraud involving affirmative dishonesty”) (quoting Cataphote Corp. v. DeSoto Chem. Coatings, Inc., 450 F.2d 769, 772, 171 USPQ 736, 738 (9th Cir.1971)); Bendix Corp., 421 F.2d at 819, 164 USPQ at 493. The Supreme Court in Walker Process was quite explicit in premising antitrust liability on knowing and willful misrepresentations, but not on other types of misconduct that might render a patent unenforceable such as the failure to disclose material prior art. The Court expressly discussed only knowing and willful misrepresentations, contrasted with good faith or honest mistakes, or mere “technical” fraud; it did not deal with inequitable conduct involving even a knowing failure to disclose a material reference. Accordingly, the inventors’ failure to disclose the 1977 Book, even if that failure was known by NP, cannot support the imposition of antitrust liability on NP based on Walker Process fraud.
The dissent asserts that a finding of antitrust liability under Walker Process may be premised on an omission coupled with a duty of disclosure. We disagree. It is of course true that an applicant for a patent owes a duty of candor to the PTO, see 37 C.F.R. § 1.56 (1996), and that breach of a duty can constitute common law fraud. However, Walker Process and its progeny, which are applicable to a broad array of administrative contexts, see, e.g., Clipper Exxpress, 690 F.2d at 1260-61 (extending Walker Process doctrine “to cases not arising in a patent context”), draw a line between omissions and affirmative misrepresentations. We choose not to breach that line. Allegations of inequitable conduct are a staple these days in pleadings attacking patents or defending against charges of patent infringement. Alleged failure to disclose prior art, whether or not material or intentional, is the basis for many of these charges. Were we to hold that failure to cite prior art provides a basis for Walker Process antitrust liability, most patent infringement actions would be converted into antitrust cases, the shield of inequitable conduct into the sword of antitrust liability. See Korody-Colyer Corp. v. General Motors Corp., 828 F.2d 1572, 1578, 4 [1474]*1474USPQ2d 1203, 1207 (Fed.Cir.1987). We do not believe that the Supreme Court intended Walker Process to effect that result. Failure to cite prior art is not Walker Process fraud.
The evidence also indicates that NP’s suit could not be found to be objectively baseless and therefore was not a sham. The jury’s finding that NP knew that the patent was either invalid or unenforceable when it brought suit is insufficient to support antitrust liability. The evidence, especially Dr. Green’s testimony that he was told that “if the Patent Office did not receive a copy of [the 1977 Book], and if that were true, then we would have a larger problem and that was fraud,” may support a conclusion that NP subjectively believed that the suit would be baseless or brought the suit in bad faith. However, the evidence would not support a jury verdict that such a suit was objectively baseless. See Creek v. Village of Westhaven, 80 F.3d 186, 192 (7th Cir.1996) (citing PRE for the proposition that “[s]uits that are objectively baseless, that is, frivolous suits, as distinct from colorable suits brought in bad faith, are not constitutionally protected.”).
The conduct in question was a failure to cite possibly relevant prior art, which relates to inequitable conduct. A conclusion of inequitable conduct requires an equitable weighing by the court of the factual issues of intent to deceive and materiality of alleged omissions or misrepresentations in view of the totality of circumstances. See Molins PLC v. Textron, Inc., 48 F.3d 1172, 1178-79, 33 USPQ2d 1823, 1826-27 (Fed.Cir.1995); Akzo N.V. v. United States Int’l Trade Comm’n, 808 F.2d 1471, 1481-82, 1 USPQ2d 1241, 1247 (Fed.Cir.1986). Thus, by its very nature, a court’s ultimate conclusion of inequitable conduct is not predictable. Therefore, an omission that might later be found to constitute inequitable conduct, such as the failure to disclose the 1977 Book in this case, cannot as a matter of law be the basis for finding that an infringement suit was objectively baseless.
Furthermore, contrary to the dissent’s assertion, the 1977 Book did not “essentially describe and illustrate the invention.” Rather its disclosure of micropits having the claimed diameter and spacing was not explicit and was only made apparent after 31, during litigation, measured highly enlarged copies of the SEMs depicted in the 1977 Book. Based on this limited disclosure, NP raised bona fide arguments that the 1977 Book did not render the patent invalid and that the failure to disclose the 1977 Book did not render the patent unenforceable. Thus, NP could have had an objectively reasonable expectation that it could prevail on the merits. Also, significantly, NP had asserted the ’891 patent against two other parties, and apparently overcame motions for summary judgment of invalidity and unenforceability in those suits. Cf. PRE, 508 U.S. at 64-65, 113 S.Ct. at 1930-31 (“Even though it did not survive PRE’s motion for summary judgment, Columbia’s copyright action was arguably ‘warranted by existing law1 or at the very least was based on an objective ‘good faith argument for the extension, modification, or reversal of existing law.’ Fed. Rule Civ. Proc. 11.”). These facts belie a conclusion that a reasonable litigant in NP’s position would have known that the patent would inevitably be held invalid or unenforceable. As this court and others have cautioned, a patentee must be allowed to test the validity or enforceability of its patent, even if it fears that the patent may be invalid or unenforceable. See Loctite Corp. v. Ultraseal Ltd., 781 F.2d 861, 876-77, 228 USPQ 90, 101 (Fed.Cir.1985) (noting “the public policy of erecting a barrier against thwarting patentees from asserting legitimate patent rights”); Handgards, Inc. v. Ethicon, Inc., 601 F.2d 986, 993, 202 USPQ 342, 348 (9th Cir.1979) (“Pat-entees must be permitted to test the validity of their patents in court through actions against alleged infringers.”). The imposition of antitrust liability on NP in this case would thwart its entitlement to test the validity and scope of its patent.
As the Supreme Court admonished in PRE, “a court must ‘resist the understandable temptation to engage in post hoc reasoning by concluding’ that an ultimately unsuccessful ‘action must have been unreasonable or without foundation.’ ” 508 U.S. at 61 n. 5, 113 S.Ct. at 1928 n. 5 (citing Christiansburg Garment Co. v. EEOC, 434 U.S. 412, 422, 98 S.Ct. 694, 701, 54 L.Ed.2d 648 (1978) (“Even [1475]*1475when the law or the facts appear questionable or unfavorable at the outset, a party may have an entirely reasonable ground for bringing suit.”)). The dissent has fallen prey to this “understandable temptation.” NP may have lost its suit, but the record indicates that a “similarly situated reasonable litigant could have perceived some likelihood of success.” PRE, 508 at 62-65, 113 S.Ct. at 1929-31. That is all that is needed to provide Noerr immunity. See PRE, 508 U.S. at 60, 113 S.Ct. at 1928 (stating that to support antitrust liability, a suit must be “objectively baseless in the sense that no reasonable litigant could realistically expect success on the merits [or] could conclude that the suit is reasonably calculated to elicit a favorable outcome.”); id. at 69, 113 S.Ct. at 1932-33 (Stevens & O’Connor, JJ., concurring) (stating that no antitrust liability should arise from a suit in which the plaintiffs “invoked the federal court’s jurisdiction to determine whether they could lawfully restrain competition from competitors”). Accordingly, because NP’s suit was reasonably calculated to elicit a favorable outcome, not merely to impose collateral harm on 31, the suit was not a sham and was thus entitled to Noerr immunity-
Because the evidence cannot support a verdict that the patent was obtained by Walker Process fraud, or that NP’s infringement suit was objectively baseless, we reverse the district court’s decision denying NP’s motion for JMOL on 3I’s antitrust counterclaim and instruct the court to grant the motion.
CONCLUSION
The district court did not err in holding the ’891 patent invalid as a matter of law at the close of NP’s case-in-chief because NP itself introduced evidence that was fatal to the patent’s validity. However, the district court erred in denying NP’s motion for JMOL on 3I’s antitrust counterclaim. No reasonable jury, applying the correct law, could have found that the facts were sufficient to strip NP of its antitrust immunity. The evidence of record does not support a conclusion that the ’891 patent was obtained by fraud within the meaning of Walker Process or that NP’s suit was objectively baseless.
COSTS
No costs.
AFFIRMED-IN-PART and REVERSED-IN-PART.