By Cory G. Smith, George C. Chen and Ellen Komlos
The U.S. Court of Appeals for the Federal Circuit recently addressed the usage of the doctrine of collateral estoppel in patent infringement cases. Specifically, the court considered whether a finding of invalidity of claims by the U.S. Patent and Trademark Office’s Patent Trial and Appeal Board (PTAB) at an inter partes review (IPR) could be used to estop a patent holder from asserting patent infringement of different claims of the same patent in district court litigation. In Kroy v. Groupon, the Court reversed the trial court and held that a prior finding of invalidity at the PTAB cannot be used to estop a patent infringement suit in district court alleging infringement of different claims of the same patent.