Candor and Its Consequences: The Duty to Disclose, Inequitable Conduct, and Life After Therasense
By Casey Scott McKay ·
Inequitable conduct was once pleaded in nearly every patent case and rendered whole patents unenforceable on thin showings. Therasense changed that, and the modern doctrine is narrow, hard to plead, and still capable of destroying a portfolio. This article sets out who is actually bound by the duty of candor, what materiality now means, and why the affirmative egregious misconduct exception is the only route that does not require but-for proof. It explains the specific intent standard and the single-most-reasonable-inference rule that makes intent the harder element. It then works the practical side - what to disclose and when, cross-citation across a family, the litigation overlap that generates most real problems, and supplemental examination as the cure. It closes with the failure modes that still produce unenforceability findings.
IP and Technology > Patent Counseling Transactions | Article | Published 12 March 2024 - Updated 18 December 2025 | Casey Scott McKay - marksy.us
Summary. Inequitable conduct was once pleaded in nearly every patent case and rendered whole patents unenforceable on thin showings. Therasense changed that, and the modern doctrine is narrow, hard to plead, and still capable of destroying a portfolio. This article sets out who is actually bound by the duty of candor, what materiality now means, and why the affirmative egregious misconduct exception is the only route that does not require but-for proof. It explains the specific intent standard and the single-most-reasonable-inference rule that makes intent the harder element. It then works the practical side — what to disclose and when, cross-citation across a family, the litigation overlap that generates most real problems, and supplemental examination as the cure. It closes with the failure modes that still produce unenforceability findings.
Keywords: duty of candor · Rule 56 · who is bound · materiality · but-for materiality · affirmative egregious misconduct · specific intent to deceive · single most reasonable inference · Therasense · sliding scale abolished · Exergen pleading · information disclosure statement · IDS timing and fees · cross-citation across a family · litigation overlap · inventor declarations · supplemental examination · unclean hands · unenforceability · portfolio infection
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