Federal Circuit Revisits Assignor Estoppel

• Published date: 19 August 2022
• Law Firm: Oblon, McClelland, Maier & Neustadt, L.L.P
• Author: Mr Richard D. Kelly

On August 11, 2022, the Federal Circuit issued its opinion in the remand of Hologic, Inc. v Minerva Surgical, Inc. from the Supreme Court's decision limiting the application of assignor estoppel to where the assignor is taking in litigation a position inconsistent with his prior representations in assigning the patent. In this case the issue was whether the issued claims are materially broader than the claims in the assigned application, Minerva Surgical, Inc. v. Hologic, Inc., 141 S. Ct. 2298, 2302, 2309 (2021). The Supreme Court in Minerva refused to discard the concept of assignor estoppel but instead held that the concept comes with limits and "reaches only as far as the equitable principle long understood to lie at its core." The Supreme Court held that assignor estoppel "applies only when an inventor says one thing (explicitly or implicitly) in assigning a patent and the opposite in litigating against the patent's owner." Id. at 2304. Stated differently, where the assignor has not any explicit or implicit representations which conflict with an invalidity defense.

In this case Minerva asserted that the challenged claim in the assigned patent was materially broader than the ones assigned the original application and thus representations as to the claims existing at the time of the...