Don’t ‘Estop’ My Patent: New Claims Still Take the Stand

3.26.25

In early February, the Federal Circuit clarified in Kroy IP Holdings, LLC v. Groupon, Inc. that a PTAB decision invalidating certain patent claims under the preponderance standard does not automatically bar litigation of unadjudicated claims in district court, where the higher clear-and-convincing standard applies.[1]

At the district court, Groupon successfully argued that Kroy’s new claims were immaterially different from the invalidated claims of U.S. Patent No. 6,061,660, making them subject to collateral estoppel. However, the Federal Circuit reversed the district court’s dismissal, emphasizing that invalidity must be proven anew under the clear-and-convincing evidence standard. The court relied on precedent from Parkervision v. Qualcomm, which underscores that collateral estoppel does not apply when a higher burden of proof is required in the subsequent forum.

The Federal Circuit distinguished its holding from prior cases that apply collateral estoppel more broadly. In XY v. Trans Ova Genetics, the court held only that claims definitively ruled unpatentable by the PTAB cease to exist, preventing their reassertion. That principle, however, does not extend to other, unadjudicated claims. Likewise, Ohio Willow Wood v. Alps S. involves district-court-to-district-court collateral estoppel, where the same clear-and-convincing standard applies to both litigations. Since the PTAB uses a lower standard, Ohio Willow Wood does not apply collateral estoppel to assertions of unadjudicated claims when similar claims are invalidated by the PTAB.

This case presents two important takeaways. First, litigants who want to avoid litigating unadjudicated claims later should challenge all relevant claims at the PTAB during the IPR window. Once that window closes, patentees can still assert unadjudicated claims in district court, effectively forcing defendants to meet a more rigorous burden of proof. Second, patentees may seek to exploit this distinction by strategically holding back certain claims until after the IPR window.

Samuel Raque | Associate Attorney