The U.S. Supreme Court held that assignor estoppel applies only when the assignor's claim of invalidity contradicts explicit or implicit representations made in assigning the patent. Minerva Surgical, Inc. v. Hologic, Inc., No. 20-440 (June 29, 2021). Inventor Truckai assigned his invention--a device to treat abnormal uterine bleeding--to his company. The issued patent along with its portfolio patents was bought by Hologic. Truckai then developed an improved device and assigned it to Minerva Surgical. Hologic filed a continuation application that included a claim to encompass Truckai's improved device and the application issued as patent. Hologic sued Minerva and Minerva contended that the newly added claim was invalid under 112 for lack of written description. Hologic invoked doctrine of assignor estoppel.
The district court agreed that assignor estoppel barred Minerva's defense and the Federal Circuit affirmed in part. Minerva filed a writ. In a 5-4 decision, Justice Kagan reasoned that courts have long applied the doctrine of assignor estoppel to deal with inconsistent representations about patent validity.
The Court also recognized limits to assignor estoppel: (1) assignment occurs before inventor can make warranty of validity to patent claims, e.g., employee assigning rights in future inventions (2) later legal development renders the warranty as irrelevant (3) post-assignment change in patent claims, e.g., inventor assigns patent application and later to broaden the scope of claims.
Full text of the opinion is available here.
The district court agreed that assignor estoppel barred Minerva's defense and the Federal Circuit affirmed in part. Minerva filed a writ. In a 5-4 decision, Justice Kagan reasoned that courts have long applied the doctrine of assignor estoppel to deal with inconsistent representations about patent validity.
The Court also recognized limits to assignor estoppel: (1) assignment occurs before inventor can make warranty of validity to patent claims, e.g., employee assigning rights in future inventions (2) later legal development renders the warranty as irrelevant (3) post-assignment change in patent claims, e.g., inventor assigns patent application and later to broaden the scope of claims.
Full text of the opinion is available here.
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