Legal Definitions - inter partes reexamination

Definition:Inter partesreexamination is a legal process in which the U.S. Patent and Trademark Office reviews an already-issued patent to determine if it is valid based onprior art. This process can be initiated by anyone, including the patent holder or an anonymous informant, at any time during the life of the patent. Only patents and publications can be considered as prior art.

Example: A company is accused of infringing on a patent held by another company. The alleged infringer seeks inter partes reexamination of the patent to prove that it is invalid based on prior art. The U.S. Patent and Trademark Office reviews the patent and determines whether it is valid or not.

This example illustrates how inter partes reexamination can be used to challenge the validity of a patent and avoid liability for infringement.