2025 Federal Circuit IP Appeals: Ingenico Inc. v. IOENGINE, LLC, 136 F.4th 1354 (Fed. Cir. 2025) (Dyk, Prost, Hughes)

Ingenico provided a definitive resolution to a decade-long split among district courts regarding the scope of inter partes review (IPR) estoppel. The court’s ruling centers on a technical but vital distinction between a legal “ground” of invalidity and the evidence used to prove the ground.

IOENGINE accused Ingenico of infringing several patents directed to portable USB-type communication devices. While Ingenico successfully invalidated many claims through IPR proceedings at the Patent Trial and Appeal Board (PTAB), several claims survived to a jury trial in the District of Delaware.

At trial, Ingenico argued that the remaining claims were invalid based on a prior art system, the DiskOnKey, that was in “public use” or “on sale” before the patent’s priority date. IOENGINE sought to block this invalidity defense under the IPR estoppel statute, 35 U.S.C. § 315(e)(2). That statute provides that the petitioner in an IPR that results in a final written decision “may not assert” in district court that any claim challenged in the IPR “is invalid on any ground that the petitioner raised or reasonably could have raised during” the IPR. IOENGINE argued that the DiskOnKey’s features were fully described in manuals and “Readme” files — which are printed publications — and that therefore Ingenico was estopped from relying on the DiskOnKey device in district court because it could have used the underlying documents in its IPR. The district court rejected this argument and allowed Ingenico to present this defense.

The Federal Circuit affirmed, holding that estoppel did not apply to the DiskOnKey “system art.” The court clarified that a “ground” under 35 U.S.C. § 315(e)(2) refers to a legal theory of invalidity, not the prior art itself. The Federal Circuit explained that “[g]rounds are the theories of invalidity available to challenge a claim under §§ 102 and 103,” whereas prior art is “evidence of a ground” and “not coextensive with [the] ground.”

The Federal Circuit also relied on 35 U.S.C. § 311(b), which restricts IPRs to challenges based on “prior art consisting of patents or printed publications.” Because “public use” and “on-sale” grounds cannot be raised in an IPR, the court held that a party cannot be estopped from raising these distinct invalidity theories later in district court. Significantly, the Federal Circuit held that a party may use the exact same documents from an IPR in district court so long as it uses them as evidence of a different invalidity ground: “IPR estoppel … does not preclude a petitioner from relying on the same patents and printed publications as evidence in asserting a ground that could not be raised during the IPR.”

Previously, some district courts had estopped defendants from using physical devices if they were “materially identical” to printed publications describing the devices. This test is now effectively dead. Instead, the inquiry centers on whether the specific ground of invalidity at issue could have been raised in an IPR. If not, it is fair game in district court.

Related: 

Kroy IP Holdings, LLC v. Groupon, Inc., 127 F.4th 1376 (Fed. Cir. 2025) (holding that a PTAB finding of unpatentability in an IPR does not collaterally estop a patent owner from asserting different, even “immaterially different,” claims of the same patent in district court, because the burden of proof in an IPR is lower than the burden of proof for invalidity in district court).

This article appeared in the 2025 Federal Circuit IP Appeals: Summaries of Key 2025 Decisions report.