On appeal, the Federal Circuit explained that collateral estoppel applies when (1) the issue at stake is identical to the issue involved in the prior proceeding; (2) the issue was actually litigated in the prior proceeding; (3) the determination of the issue must have been a critical and necessary part of the prior judgment and (4) the party against whom it is asserted must have had a full and fair opportunity to litigate the issue in the prior proceeding.
