Prosecution history estoppel

Prosecution history estoppel, also known as file-wrapper estoppel, is a term used in United States patent law to indicate that a person who has filed a patent application, and then makes amendments to the application to accommodate the patent law, has no cause of action for infringement to the pre-amendment patent claims that were amended.

Prosecution history estoppel is a bar to the use of the doctrine of equivalents, but only to the extent that the amendments were made with the intent of narrowing the claims made in the patent, so as to avoid some problem that would void an overbroad patent, such as overlap with a different patent.