In 2016, the Federal Circuit expressed doubt that claim constructions from the PTAB could give rise to estoppel in later litigation because “the [PTAB] applies the broadest reasonable construction of the claims while the district courts apply a different standard of claim construction as explored in Phillips.” SkyHawke Techs., LLC v. Deca Int’l Corp., 828 F.3d 1373, 1376 (Fed. Cir. 2016). But that distinction does not apply if the PTAB applies the Phillips standard to construe claim terms, as one district court explained in finding that it was collaterally estopped from apply a claim construct different from that applied by the PTAB. Regents of the Univ. of Minn. v. LSI Corp., No. 5:18-cv-00821-EJD, 2023 WL 5520958 (N.D. Cal. Aug. 25, 2023). In that case, the University of Minnesota sued LSI for infringement of its patent covering certain digital storage systems. LSI sought inter partes review, and the district court suit was stayed. The PTAB found certain independent claims unpatentable, and its determination was affirmed by the Federal Circuit. The district court lifted the stay to determine whether LSI should be held liable for infringing certain dependent claims that survived inter partes review.
Before the district court, the University argued for a construction of the claim term “transition” that was different from that the plain and ordinary meaning applied by the PTAB. The district court held, however, that it was estopped from applying a different construction. First, the district court explained that “the concerns highlighted in Skyhawk are not present” because the PTAB “applied the same Phillips standard the Court applies now.” 2023 WL 5520958, at *7. Second, the court applied the regional circuit’s standard for collateral estoppel, in this case, the Ninth Circuit:
Defendants must show “(1) the issue necessarily decided at the previous proceeding is identical to the one which is sought to be relitigated; (2) the first proceeding ended with a final judgment on the merits; and (3) the party against whom collateral estoppel is asserted was a party or in privity with a party at the first proceeding.”
Id. The parties did not dispute whether the second and third elements were met because the claim term at issue and the parties involved in the IPR were the same. Id. at *8. The University, however, contested is whether the construction of the term was “necessarily decided” because the prior construction “did not logically require the PTAB to reject the alternate construction that UMN advances now.” Id. The district court was not persuaded. It explained that ”[t]he requirement that an issue be “necessarily decided” means only that the previous tribunal actually decided the issue by hearing evidence and argument from both parties and specifically ruling on it. Because the PTAB had expressly addressed and rejected the University’s alternate construction, the district court held “the issue was ‘necessarily decided’” and collateral estoppel applied.