What doctrine bars relitigation of the same patent validity issue against a new defendant after a prior adverse decision?

What doctrine bars relitigation of the same patent validity issue against a new defendant after a prior adverse decision?

• A. Res judicata
• B. Patent exhaustion
• C. Patent misuse
• D. Collateral estoppel

Answer: (D)

Collateral estoppel, or issue preclusion, is the rule that prevents relitigating a specific issue that was actually litigated and essential to a previous judgment. In the patent context, once a court has decided a patent validity issue in an earlier case, that same issue cannot be relitigated against a new defendant in a later suit if the prerequisites are met: the issue is identical, it was actually litigated and fully and fairly litigated, and it was necessary to the prior decision. This promotes finality and efficiency, stopping multiple parties from reopening the same validity question. Res judicata would cover claims rather than the specific issue and typically involves the same parties or those in privity, so it’s broader in scope and would not, by itself, bar relitigation of a lone validity issue against a new defendant. Patent exhaustion concerns whether patent rights are exhausted after a sale, not about blocking relitigation of validity. Patent misuse addresses improper behavior by the patentee in enforcing rights, not the procedural bar against repeating the validity issue.

Collateral estoppel, or issue preclusion, is the rule that prevents relitigating a specific issue that was actually litigated and essential to a previous judgment. In the patent context, once a court has decided a patent validity issue in an earlier case, that same issue cannot be relitigated against a new defendant in a later suit if the prerequisites are met: the issue is identical, it was actually litigated and fully and fairly litigated, and it was necessary to the prior decision. This promotes finality and efficiency, stopping multiple parties from reopening the same validity question.

Res judicata would cover claims rather than the specific issue and typically involves the same parties or those in privity, so it’s broader in scope and would not, by itself, bar relitigation of a lone validity issue against a new defendant. Patent exhaustion concerns whether patent rights are exhausted after a sale, not about blocking relitigation of validity. Patent misuse addresses improper behavior by the patentee in enforcing rights, not the procedural bar against repeating the validity issue.