A more thorough explanation:

Definition: Nonmutual collateral estoppel is a legal doctrine that prevents a party from relitigating an issue that has already been decided in a previous lawsuit, even if the second lawsuit involves a different claim. This doctrine can be asserted either offensively or defensively by a nonparty to the earlier action to prevent a party from relitigating an issue that was determined against it.

Examples:

• Defensive collateral estoppel: A defendant in a personal injury lawsuit is sued by the plaintiff for damages resulting from a car accident. The defendant was previously sued by another plaintiff for the same accident and was found not to be at fault. The defendant can assert defensive collateral estoppel to prevent the plaintiff in the current lawsuit from relitigating the issue of fault.
• Offensive collateral estoppel: A plaintiff sues a company for patent infringement. The company previously litigated the same issue in a different lawsuit and was found to have infringed on the patent. The plaintiff can assert offensive collateral estoppel to prevent the company from relitigating the issue of infringement.

These examples illustrate how nonmutual collateral estoppel can be used to prevent parties from relitigating issues that have already been decided in previous lawsuits. This doctrine helps to promote judicial efficiency and finality of judgments.