Collateral estoppel prevents the relitigation of any issues necessarily and unambiguously determined in a prior litigation from being relitigated again in a subsequent litigation. It can be used either defensively or offensively.
When a defendant attempts to use collateral estoppel, he or she is saying that the plaintiff is precluded from arguing some claim because it was determined previously. When a plaintiff attempts to use collateral estoppel, he or she is saying that a defendant is precluded from making a defensive argument. The law disfavors the latter situation.
Specifically, “offensive collateral estoppel is disfavored by courts, and it will not be applied when doing so would be inequitable.”“[O]ffensive collateral estoppel normally involves the attempt by a plaintiff to rely on a prior adjudication of an issue to prevent the defendant from challenging a fact necessary to the plaintiff’s case and on which the plaintiff carries the burden of persuasion.” Parklane Hosiery Co. v. Shore, 439 U.S. 322, 329 (1979).
From a procedural prospective, collateral estoppel must be pleaded if a party intends to argue or rely upon it. Brown v. Carnahan, 370 S.W.3d 637, 659 (Mo. 2012).