“Collateral estoppel is a specialized aspect of the doctrine of res judicata, sometimes spoken of as a “ ‘secondary aspect’ ” of res judicata, as a “specific aspect of res judicata,” and as a “subsidiary form” of res judicata.
While res judicata holds that a final valid judgment on the merits in favor of or against a litigant is a complete bar to further litigation on the same cause of action or defense by the same parties or their privies, collateral estoppel expands the barrier to preclude these parties from relitigating issues actually determined against them in the first action on any cause of action even if very different from the causes of action previously litigated. California applies collateral estoppel or issue preclusion when the issue determined in the prior adjudication is identical to that presented in a subsequent action, the prior adjudication resulted in a determination on the merits, and the party against whom the collateral estoppel is asserted was a party or in privity with a party in the prior adjudication. In a significant expansion of the application of the res judicata barrier to relitigation, the party asserting collateral estoppel need not have been a party or privy to a party in the prior action.”
[California Affirmative Defenses [certain citations omitted]]
