Patent Inequitable Conduct: When Disclosure Misconduct Makes a Patent Unenforceable
A patent can survive validity challenges and still become unenforceable if it was procured through inequitable conduct. The doctrine is serious, but it is also frequently overstated. A missed reference, an incorrect statement, or a poor disclosure decision does not automatically establish inequitable conduct. Federal Circuit law requires proof of both materiality and a specific intent to deceive the U.S. Patent and Trademark Office.
That distinction matters to both sides of a patent dispute. Patent owners need to understand which prosecution facts create real enforceability risk. Accused infringers need more than suspicion before pleading a fraud-based defense. And inventors, patent counsel, and company personnel need disclosure systems that address problems while an application is pending rather than trying to reconstruct decisions years later.
What is patent inequitable conduct?
Inequitable conduct is an equitable defense to patent infringement. It generally concerns a material misrepresentation or omission made during prosecution with the specific intent to deceive the USPTO. If proven, the consequence is not simply cancellation of one claim. The patent may be held unenforceable.
The defense is related to—but distinct from—the duty of candor and good faith in 37 C.F.R. § 1.56. Rule 56 governs conduct before the USPTO and requires individuals associated with prosecution to disclose known information material to patentability. Inequitable conduct is a litigation doctrine applied by courts after the patent issues.
The standards are therefore not interchangeable. The USPTO’s disclosure rule defines materiality for examination and encourages candid submission of relevant information. In litigation, the Federal Circuit’s en banc decision in Therasense, Inc. v. Becton, Dickinson & Co. tightened the inequitable-conduct standard to curb overuse of the defense. A court ordinarily must find but-for materiality and specific deceptive intent, and it must analyze those elements separately.
Materiality and intent are different questions
The two elements ask different things:
| Element | Core question | Typical evidence |
|---|---|---|
| But-for materiality | Would the USPTO have allowed the claim if it had known the withheld information? | The claims, withheld information, cited art, prosecution positions, and expert testimony about what the information teaches |
| Specific intent | Did a particular individual know the information was material and deliberately decide to withhold or misrepresent it to deceive the USPTO? | Emails, draft declarations, testimony, document history, instructions to counsel, timing, and evidence bearing on alternative explanations |
A strong showing on materiality cannot compensate for weak proof of intent. Nor does suspicious intent make immaterial information but-for material. The former “sliding scale” approach no longer controls.
What does but-for materiality require?
For withheld prior art, the general inquiry is whether the USPTO would have denied a claim had it known of the information. A reference is not but-for material when it is merely cumulative of information already before the examiner. That makes the analysis claim-specific and technically demanding: the court must compare what the withheld material actually teaches with the claims and the existing prosecution record.
The Federal Circuit’s February 26, 2026 decision in Global Tubing LLC v. Tenaris Coiled Tubes LLC illustrates the point. The district court had granted summary judgment that several patents involving coiled tubing were unenforceable. The Federal Circuit vacated that judgment because genuine factual disputes remained over both materiality and intent.
On materiality, the parties disputed whether withheld CYMAX documents added something important beyond a reference that had been submitted to the examiner. Because a reasonable factfinder could find the withheld material cumulative, summary judgment was improper. The ruling does not decide that there was no inequitable conduct. It confirms that materiality cannot be assumed merely because a challenger has identified an undisclosed document.
But-for materiality also has a narrow exception for affirmative egregious misconduct. A deliberately false affidavit is the classic example. The exception prevents a party from escaping the doctrine merely because a calculated falsehood cannot be tested through the ordinary but-for inquiry. Courts do not treat every inaccurate statement as egregious misconduct; the facts and the speaker’s intent still matter.
Specific intent is a demanding evidentiary burden
The intent element requires proof that a particular person knew of the information, knew it was material, and deliberately decided to withhold it. Negligence, gross negligence, and a “should have known” theory are insufficient. When intent is inferred from circumstantial evidence, deceptive intent must be the single most reasonable inference that can be drawn.
This does not mean intent can be proven only by an admission. Direct evidence of a plan to mislead the USPTO is rare. Courts can consider circumstantial evidence, credibility, and the record as a whole. But when a reasonable nondeceptive explanation fits the evidence, the required inference may not be available.
Global Tubing again provides a useful example. A technical declarant reviewing a draft submission wrote that he was “not sure it is a good idea to disclose” certain documents. The statement was plainly important evidence, and a factfinder could view it as supporting deceptive intent. Yet the declarant also offered an explanation tied to his understanding that the documents concerned a different carbon range. At summary judgment, the court had to view the evidence in the nonmoving party’s favor. The Federal Circuit held that a genuine dispute remained over whether deception was the single most reasonable inference.
Similarly, in Freshub, Inc. v. Amazon.com, Inc., a statement in a petition to revive an abandoned application was material, but the challenger did not prove clearly and convincingly that the statement was false or made with the specific intent to deceive. The court affirmed rejection of the inequitable-conduct defense. Materiality alone did not establish intent.
The pleading must identify a real misconduct theory
Inequitable conduct sounds in fraud, so Federal Rule of Civil Procedure 9(b) applies. Under Exergen Corp. v. Wal-Mart Stores, Inc., a pleading should identify the specific who, what, when, where, and how of the alleged material misrepresentation or omission. Knowledge and intent may be alleged generally, but the pleading still needs enough underlying facts to support a reasonable inference that a particular person knew of the information and acted with deceptive intent.
A generic allegation that “the applicant” failed to cite important art is vulnerable. A workable theory ordinarily identifies:
- the individual who allegedly engaged in the conduct;
- the specific information, claim limitations, and prosecution event involved;
- where the material information appears and how it differs from what the examiner already had; and
- facts supporting knowledge and a deliberate decision to mislead.
This particularity requirement is more than a drafting technicality. It forces the accused infringer to connect the prosecution record to a plausible intent theory before the defense expands discovery into the communications and decision-making of inventors, prosecutors, and company personnel.
What evidence matters in an inequitable-conduct investigation?
The patent file is only the starting point. A serious investigation usually compares the application, claim amendments, examiner interviews, declarations, and cited references with information outside the public record. That may include prior-art searches, foreign search reports, related applications, product testing, sales activity, internal presentations, technical papers, and communications with inventors or prosecution counsel.
The timeline often matters as much as the documents. When did a person learn of the information? Which claims were pending at that time? What did the person understand the document to teach? Was the same information already before the examiner? Did the person send it to counsel? Were inconsistent positions taken in another application, a regulatory submission, or litigation?
Those questions should be evaluated alongside the disputed claim language. Tucker Law’s overview of patent claim construction explains why the meaning of a limitation can control infringement and validity issues. It can also affect whether withheld information was truly material to a pending claim.
Good prosecution practices reduce later uncertainty
The best time to address disclosure risk is during prosecution. A company should identify who is substantively involved, explain the duty of candor, and create a reliable path for potentially material information to reach patent counsel. The process should connect U.S. prosecution with related foreign cases, continuation practice, technical teams, and disputes involving the same technology.
That does not require reflexively submitting every document ever collected. It does require informed review. Teams should preserve when an item was received, who evaluated it, whether similar information was already of record, and what action was taken. If a statement or submission appears inaccurate, counsel should assess available corrective procedures promptly rather than waiting for enforcement.
A coordinated patent-application strategy helps keep inventors, company personnel, and counsel aligned as claims change. The USPTO’s MPEP Chapter 2000 collects the agency’s guidance on the duty of disclosure, related applications, litigation, and other sources of potentially material information.
Litigation strategy differs for patent owners and accused infringers
A patent owner evaluating enforcement should review enforceability before filing suit, especially when the prosecution history includes late-discovered references, declarations, petitions to revive, related foreign proceedings, or inconsistent technical positions. The review should not begin and end with whether an IDS was filed. It should test whether any omitted information was but-for material and whether the evidence could support a particularized intent theory.
An accused infringer should resist treating inequitable conduct as a routine companion to invalidity. The defense can be powerful, but it requires its own proof. Technical prior-art analysis, prosecution chronology, witness knowledge, and documentary evidence must fit together. The 2026 Global Tubing decision also shows why disputed intent and cumulative-art questions may be difficult to resolve on summary judgment.
These issues can affect case framing, discovery, expert work, settlement, and trial. Tucker Law’s patent-litigation practice addresses infringement, validity, damages, and enforceability as connected parts of the same dispute. The firm also serves as Florida patent-litigation local counsel for parties and national counsel litigating in Florida’s federal courts.
The bottom line
Inequitable conduct is not established by hindsight or by the mere existence of an undisclosed reference. A challenger ordinarily must prove that the information was but-for material and that a specific individual deliberately acted with the intent to deceive the USPTO. Those elements remain separate, and both depend on a detailed factual record.
If a prosecution issue has surfaced before enforcement, or an inequitable-conduct allegation has been raised in litigation, contact Tucker Law to evaluate the claims, prosecution record, technical evidence, and procedural options.
