## Facts

- Therasense, Inc. (later Abbott Diabetes Care, Inc.) and Abbott Laboratories asserted U.S. Patent No. 5,820,551 covering disposable electrochemical blood glucose test strips configured for whole blood testing without a protective membrane.
- During prosecution, Abbott distinguished its own earlier U.S. Patent No. 4,545,382 by arguing the earlier patent required a protective membrane, so it did not anticipate the membrane-less claims.
- In separate European proceedings involving a counterpart patent, Abbott’s representatives stated that the membrane was “optional.”
- Abbott did not disclose the European submissions containing the “optional membrane” statements to the USPTO during prosecution of the ’551 patent.
- In consolidated litigation, accused infringers raised inequitable conduct based on the nondisclosure of the European statements.
- The district court held the ’551 patent unenforceable for inequitable conduct, finding the European submissions highly material and finding intent to deceive.
- A Federal Circuit panel affirmed; the court then granted rehearing en banc to reconsider inequitable conduct standards.

## Issues

1. What level of intent must be proven to establish inequitable conduct.
2. What materiality standard governs inequitable conduct, including whether but-for materiality is required.
3. Whether courts may apply a “sliding scale” that allows strong materiality to compensate for weak intent evidence (and vice versa).
4. Whether any exception exists to but-for materiality for especially serious misconduct.

## Decision

- The en banc Federal Circuit vacated the judgment of unenforceability and remanded for reconsideration under revised standards.
- Inequitable conduct requires proof by clear and convincing evidence of both:
  - specific intent to deceive the USPTO, and
  - but-for materiality as the general rule.
- The court rejected the “sliding scale” approach linking intent and materiality.
- The court recognized a narrow exception to but-for materiality for affirmative egregious misconduct (e.g., filing an unmistakably false affidavit).

## Legal Principles

- Inequitable conduct requires clear and convincing evidence that the applicant made a deliberate decision to withhold or misrepresent known material information with the specific intent to deceive the USPTO.
- Negligence and gross negligence do not satisfy the intent element; intent must be the single most reasonable inference drawn from the evidence.
- Materiality is generally but-for materiality: whether the USPTO would have allowed the claim had it known of the withheld information.
- Intent and materiality are separate requirements; a strong showing of one cannot compensate for a weak showing of the other.
- An exception to but-for materiality applies for affirmative egregious misconduct that directly corrupts the examination process.

## Conclusion

The en banc court narrowed inequitable conduct by requiring specific intent to deceive and but-for materiality (with a limited egregious-misconduct exception), vacating the unenforceability ruling and remanding for application of the new framework.


Therasense, Inc. v. Becton, Dickinson & Co., 649 F.3d 1276 (Fed. Cir. 2011) (en banc)