In Hologic, Inc. v. Minerva Surgical, Inc., 957 F.3d 1256 (Fed. Cir. 2020), the court upheld the doctrine of “assignor estoppel” but also found that it could be collaterally attacked via IPR since the PTO does not enforce the doctrine. The panel – led by Judge Stoll — also called for reconsideration of the doctrine “as it applies both in district court and in the Patent Office.”
The patentee in this case want the the court to broadly hold that assignor estoppel cannot be circumvented via IPR proceeding; the defendants are asking that the court go the other way and narrow assignor estoppel associated with claims added or amended after the assignment.
Pending en banc questions from the patentee:
1. Whether an assignor can circumvent the doctrine of assignor estoppel by attacking the validity of a patent claim in the Patent Office?
2. Whether the America Invents Act prohibits the doctrine of assignor estoppel.
The accused infringer asks the following:
1. Whether assignor estoppel applies when the assignee broadened claims after assignment.
[Note – I amended these questions to make them more readable – DC].
A group of 26 law professors led by Prof. Mark Lemley (Stanford) filed a petition in support of the en banc rehearing — arguing that the Federal Circuit has unduly expanded the doctrine of assignor estoppel. [LemleyAmicus]
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What the court needs to do here is recognize that “assignor estoppel” is the same defense as the longstanding property law doctrine of “estoppel by deed.” The two should be interpreted in parallel fashion.