The US Court of Appeals for the Federal Circuit vacated a summary judgment finding claims invalid, on grounds that the district court erred in applying issue preclusion based on factual findings in an inter partes review (IPR) that held other claims invalid. Inland Diamond Products Co. v. Cherry Optical Inc., Case No. 24-1106 (Fed. Cir. Oct. 15, 2025) (Prost, Reyna, Chen, JJ.)
In 2020, Inland Diamond filed a patent infringement suit against Cherry Optical asserting dependent claims of two patents. A year prior, in 2019, the Patent Trial & Appeal Board had determined that the independent claims on which the asserted dependent claims depended were unpatentable in two IPRs. During these 2019 IPRs, the Board determined that the claims now asserted at the district court were not unpatentable. The Board decision was not appealed.
The district court granted Cherry’s motion for summary judgment that the asserted claims were invalid for obviousness. The district court concluded that issue preclusion applied, so Cherry did not have to perform an independent invalidity analysis for limitations of what the district court termed unpatentable claims contained in the asserted claims. The district court’s analysis focused on limitations added by the asserted claims. The district court permitted Inland to defend the asserted claims’ validity because those claims had been adjudicated as not unpatentable in the 2019 IPRs.
Relying on issue preclusion and Cherry’s asserted prior art, the district court granted summary judgment that the asserted claims were invalid for obviousness. Inland appealed.
The Federal Circuit reversed, explaining that the district court erred in applying issue preclusion based on two 2024 decisions, ParkerVision and Kroy. In both decisions, the Federal Circuit reversed the district court’s holding for erroneous application of issue preclusion based on the Board’s factual findings. The Federal Circuit explained that facts proven under the Board’s then-lower standard of proof for unpatentability (preponderance of the evidence) cannot have issue-preclusive effects under the district court’s clear and convincing standard. The Federal Circuit distinguished cases where a claim has already been found unpatentable or invalid; in those situations, issue preclusion bars the assertion of those claims.
Applying this principle, the Federal Circuit reasoned that since the prevailing standard of proof for challenging patentability in 2019 in an IPR was lower and Inland’s asserted claims had never been determined invalid or unpatentable, the district court erred in giving issue-preclusive effect to the Board’s 2019 findings. To grant summary judgment, a district court must find that the patent challenger carried its burden under the clear and convincing standard separate from the Board’s factual findings. The Federal Circuit noted that to meet the higher standard, the evidence may be the same or similar to the evidence that led the Board to find that certain claims were unpatentable by a preponderance of the evidence.
