Background
Abbott Diabetes Care (then Therasense) held patents on a blood glucose test strip that could measure glucose levels in whole blood without requiring a protective membrane layer over the electrode. The patents were commercially important because they formed the basis of Abbott’s FreeStyle glucose monitor, a major product in the diabetes management market.
During prosecution of the patents before the USPTO, Abbott submitted declarations arguing that a skilled artisan would not read a related prior-art patent (the ‘382 patent) as requiring a protective membrane. At the same time, Abbott had argued the opposite position to the European Patent Office when defending the ‘382 patent in Europe — that the membrane was unequivocally optional. Abbott did not disclose those European submissions to the U.S. examiner. Becton Dickinson raised inequitable conduct as a defense, and the district court agreed, rendering the patents unenforceable.
The Court’s Holding
The Federal Circuit took the case en banc and fundamentally restructured the inequitable conduct doctrine. The court held that to prove inequitable conduct, a challenger must demonstrate both: (1) that the withheld information was material under a “but-for” standard — meaning the USPTO would not have allowed the claims had it been aware of the information; and (2) that the applicant acted with specific intent to deceive the USPTO, not merely that it made negligent or even grossly negligent misrepresentations or omissions.
The court rejected the longstanding “sliding scale” approach under which a showing of high materiality could compensate for weak evidence of intent, and vice versa. Each element must now be proven independently by clear and convincing evidence. The court also adopted a narrow “affirmative egregious misconduct” exception to the but-for standard for cases of direct fraud or particularly egregious conduct. On remand, the district court was instructed to reassess whether the stricter standard was met.
Key Takeaways
- Inequitable conduct now requires proof of both but-for materiality (the patent would not have issued but for the omission) and specific intent to deceive the PTO — both established by clear and convincing evidence.
- The old “sliding scale” test — under which strong materiality could compensate for weak intent — is abolished.
- Nondisclosure of an inconsistent litigation or foreign prosecution position may support an inequitable conduct finding, but only if the but-for and specific intent standards are both satisfied.
- The “plague” of routine inequitable conduct assertions in patent litigation was expressly acknowledged and curtailed by the en banc court.
Why It Matters
Before Therasense, inequitable conduct had become what the Federal Circuit itself called “an absolute plague” on patent litigation. Defendants routinely raised it as a defense in virtually every patent case, turning patent trials into mini-investigations into prosecution history. The low burden and sliding-scale approach made the defense cheap to assert and expensive to defeat.
By requiring specific intent and but-for materiality as independent showings, Therasense dramatically narrowed the defense. Patent litigants now need concrete evidence that the patentee subjectively intended to deceive the examiner — not just that information was withheld. For patent holders, this was a significant protection against opportunistic inequitable conduct assertions. For defendants with genuine evidence of deceptive prosecution conduct, the tougher standard made the defense harder to plead and prove, but more credible when well-supported. The ruling reshaped how practitioners counsel clients during patent prosecution and how litigators evaluate and assert the defense.