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Recent decisions from the Federal Circuit provide guidance on whether the PTAB must adopt a prior claim construction that is affirmed by the Federal Circuit. The answer depends on whether the doctrine of collateral estoppel applies.  


The doctrine of collateral estoppel, also known as issue preclusion, is intended to prevent a party from re-litigating an issue that was already decided in an earlier proceeding if that party had a full and fair opportunity to litigate the issue. The Federal Circuit has explained that collateral estoppel “protects a party from having to litigate issues that have been fully and fairly tried in a previous action and adversely resolved against a party-opponent.” For collateral estoppel to apply, the following four elements must be shown: “(1) the previous determination was necessary to the decision; (2) the identical issue was previously litigated; (3) the issue was actually decided in a decision that was final, valid, and on the merits; and (4) the party being precluded from relitigating the issues was adequately represented in the previous action.”Collateral estoppel applies to administrative proceedings, including AIA trials before the PTAB.

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