Minerva Surgical, Inc. v. Hologic, Inc.
Overview
Overview
The Supreme Court held 5-4 that the doctrine of assignor estoppel, which bars a patent assignor from later challenging the validity of the patent assigned, survives in modern patent law. Justice Kagan wrote for the majority, limiting the doctrine to situations where the assignment creates a direct representation that the patent is valid.
The Facts
Facts
Csaba Truckai invented a medical device used in gynecological procedures and assigned the patent to what became Hologic, Inc. Truckai later founded Minerva Surgical and developed a competing device. Hologic sued for infringement. Minerva argued in defense that the underlying patent was invalid. Hologic invoked assignor estoppel to bar Minerva and Truckai from challenging validity, arguing they could not assign what they represented to be a valid patent and then turn around and deny its validity.
The Issue
Issue
Whether the doctrine of assignor estoppel, which prevents a patent's inventor-assignor from later challenging the patent's validity in infringement litigation, remains valid law and, if so, what is its proper scope.
The Rules
Rule
Assignor estoppel is an equitable doctrine rooted in the principle that a party cannot assert a position inconsistent with one it previously took on which another party relied. The doctrine applies to patent assignors who explicitly or implicitly represented that the patent was valid at the time of assignment.
The Application
Analysis
Truckai, as the inventor and assignor, implicitly represented through his patent transfer to Hologic that the patent was valid. A representation on which Hologic relied when taking ownership and enforcing it against competitors. When Truckai later founded Minerva and challenged that same patent's validity as a defense to infringement, he sought to adopt a position directly inconsistent with his prior assignment, precisely the circumstance assignor estoppel addresses. The Court reaffirmed the doctrine applies in this context, where the assignor's business incentive to invalidate a patent he previously transferred creates an impermissible inconsistency, though it reserved narrow exceptions for purely formal assignments or challenges to claims added post-transfer.
The Conclusion
Conclusion
The ruling preserves assignor estoppel but limits it to assignments where the inventor actually made representations of validity. Assignors who transferred patents as a routine corporate formality, or whose later validity challenge is directed at claims added after the assignment, retain the right to challenge validity.
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