Inequitable Conduct

But-for materiality

The USPTO would not have allowed the claim but for the misrepresentation or omission. A reference is but-for material if it would have blocked allowance under a preponderance of evidence standard (not clear-and-convincing). This is a high standard — there is no inequitable conduct for minor or cumulative omissions.

Exception: affirmative egregious misconduct (filing a known false oath, fabricating data) is material regardless of but-for causation.

Specific deceptive intent

The applicant intended to deceive the USPTO — not mere negligence, gross negligence, or mistake. Deceptive intent must be the single most reasonable inference from the evidence. The intent prong requires that the deceitful intent be the most plausible explanation for the misconduct — it cannot be inferred simply from materiality.

Exception: the court infers intent from circumstantial evidence; highly material conduct with no credible explanation can support inference of intent in egregious cases.

Consequence: unenforceability

If both elements are proven by clear and convincing evidence, the entire patent is unenforceable — not just the affected claims. Unlike invalidity (which is claim-by-claim), inequitable conduct renders the entire patent (and potentially related patents in the same family) unenforceable.

Infectious unenforceability: courts may extend unenforceability to related patents in the same family where the same misconduct infected the prosecution of those patents.

What is inequitable conduct and what is the Therasense standard?

Inequitable conduct is a defense in patent litigation based on conduct before the USPTO during prosecution that was so dishonest that the entire patent should be unenforceable. Unlike invalidity (which strikes claims one by one), a finding of inequitable conduct renders the entire patent unenforceable — no claim can be enforced, even if every claim would otherwise be valid and infringed. The controlling standard, established by the Federal Circuit en banc in Therasense, Inc. v. Becton, Dickinson and Co. (2011), requires the defendant to prove by clear and convincing evidence: (1) But-for materiality: the USPTO would not have allowed the claim at issue but for the misrepresentation or omission. The reference or information must be material enough to have blocked allowance under a preponderance of the evidence standard. Minor, cumulative, or immaterial omissions do not meet this standard. Exception: affirmative egregious misconduct (filing a known false oath, fabricating prior art) is per se material. (2) Specific deceptive intent: the applicant must have specifically intended to deceive the USPTO — not mere oversight, negligence, gross negligence, or recklessness. Deceptive intent must be 'the single most reasonable inference' from the evidence — it cannot simply be inferred from the fact that something material was withheld. Before Therasense, the Federal Circuit used a 'sliding scale' test where high materiality could compensate for less intent. Therasense overruled the sliding scale and set higher thresholds for both elements.

What is the duty of disclosure during patent prosecution?

The duty of disclosure is codified in 37 C.F.R. § 1.56 and requires that all persons substantially involved in the preparation or prosecution of a patent application (inventors, attorneys, registered agents, and others) disclose to the USPTO all information known to them that is material to patentability. The duty applies during the entire pendency of the application — it continues as long as the application is open and new information is discovered. Who is subject to the duty: inventors (who must sign the oath/declaration certifying they are the actual inventors and they have reviewed the claims); patent attorneys and agents; in some circumstances, other persons with substantial involvement in prosecution (scientists who reviewed prior art during research). What must be disclosed: prior art — patents, publications, known prior uses or sales; prior art found by the applicant's own search; co-pending applications that might create a double-patenting issue; information about prior art that was considered in related foreign applications. How to satisfy the duty: file an Information Disclosure Statement (IDS) listing all relevant references with copies; the IDS process itself does not mean the applicant admits any reference is prior art. Best practice: file IDS comprehensively and early; update it whenever new material information is discovered; err on the side of disclosure for borderline cases — the cost of inadvertent non-disclosure (potential inequitable conduct) is far greater than the cost of listing one extra reference.

What happens if a court finds inequitable conduct?

A finding of inequitable conduct renders the affected patent completely unenforceable — the patentee cannot recover for any infringement, even for claims that are otherwise valid and directly infringed. This is more severe than a finding of invalidity, which is applied claim by claim: if claim 1 is invalid but claims 2–10 are valid, the patentee can still enforce claims 2–10. Inequitable conduct is an all-or-nothing defense: if the misconduct infects the patent, the entire patent falls. Additional consequences: (1) Infectious unenforceability: courts may extend unenforceability to related patents in the same family — continuation patents, divisionals, or foreign counterparts — where the same misconduct infected those prosecutions. The doctrine is not automatic but courts consider whether the inequitable conduct materially infected the related prosecution. (2) Attorney fees: an exceptional case finding based on inequitable conduct typically supports an award of attorney fees to the prevailing accused infringer under 35 U.S.C. § 285. (3) Antitrust exposure: 'Walker Process' antitrust claims — a patentee who enforces a patent known to have been obtained through fraud may face antitrust liability for attempted monopolization if the other Walker Process elements are met. There is no way to cure inequitable conduct after the fact. A certificate of correction can fix inventorship, but it cannot erase the record of deceptive conduct before the USPTO.

How does inequitable conduct differ from invalidity?

Invalidity and inequitable conduct are different defenses with different elements, different burdens, and different consequences: Invalidity (§ 102, § 103, § 112, § 101): challenges whether the patent's claims were properly granted — whether the claimed invention was new, non-obvious, enabled, adequately described, and directed to patent-eligible subject matter. Invalidity is proven by clear and convincing evidence (in district court) or preponderance (in IPR). Invalidity applies claim by claim — a finding that claim 1 is anticipated by prior art does not automatically invalidate claims 2–10. A patent can be partially valid. Inequitable conduct: challenges the patentee's conduct during prosecution — whether the patent was obtained through misconduct before the USPTO. Requires but-for materiality + specific deceptive intent, proven by clear and convincing evidence. Inequitable conduct applies to the entire patent — a single act of inequitable conduct in prosecution renders the patent completely unenforceable. The practical difference: defendants raise both in litigation. If invalidity succeeds, specific claims are gone. If inequitable conduct succeeds, the entire patent is gone — even the strongest, clearest claims that might not be vulnerable to invalidity. Plaintiffs fear inequitable conduct because it can take out claims they believed were bulletproof. Defendants value it because it is an 'atomic bomb' defense — one successful finding ends all litigation on that patent.

How can patent applicants avoid inadvertent inequitable conduct?

Preventing inequitable conduct requires diligent disclosure practices from the beginning of prosecution through issuance. Key practices: (1) File comprehensive IDS (Information Disclosure Statements): list every reference found in patent searches, every reference cited in related foreign applications, every reference known to inventors from their research. The cost of listing one extra reference is nothing; the cost of inadvertent omission is the entire patent. (2) Disclose related applications: all related co-pending applications (same inventors, similar subject matter, divisionals, continuations) should be disclosed; cross-reference related patent families. (3) Review declarations carefully: Rule 131 (prior invention declarations) and Rule 132 (experimental data, unexpected results) must be strictly accurate. False or misleading declarations are among the most common bases for inequitable conduct findings. (4) Train inventors on their duty: inventors often do not understand their duty of disclosure; they need to know they must disclose anything material they know about — especially prior art from their own prior work, related publications, and competitor patents. (5) Update the IDS throughout prosecution: the duty continues as long as the application is pending. If new material prior art is found after filing, disclose it promptly. (6) Document prior art searches: keeping clear records of what was searched, what was found, and what decisions were made about disclosure protects against later accusations that non-disclosure was deliberate. (7) Use competent patent counsel: the duty of disclosure applies to attorneys too; patent attorneys should review all representations in office action responses for accuracy before filing.