File Wrapper Estoppel

A restriction in the interpretation of a claim that exists because of an admission in the record by the applicant.

When one amends an application during the course of prosecuting a patent application to overcome a prior art rejection by narrowing the claims, one is precluded or estopped from asserting a broader interpretation after the patent issues. This type of estoppel clearly exists in the face of a prior art rejection, but can also exist based upon comments made in writing by the applicant and any other representations, causing one to conclude that the U.S. Patent and Trademark Office relied on certain representations regarding scope of claim in allowing the application. Under current law, file wrapper estoppel does not necessarily totally preclude the use of the doctrine of equivalents in the assertion of an infringement claim, but does substantially restrict the application of the doctrine of equivalents. This is also referred to as prosecution history estoppel.