Prosecution History Estoppel

The "file wrapper" is the set of official papers generated during prosecution of a patent application. It includes the original patent application, all of the office actions and other papers entered by the Patent Office, and all of the responses and other papers filed on behalf of the applicant.

Before discussing specific strategies for responding to various types of rejections, it is important to appreciate the seriousness of all communications with the Patent Office that might end up in the file wrapper. The basic problem is that any statement to the Patent Office "can and will be used against you". The principle is called "prosecution history estoppel", or sometimes "file wrapper estoppel". Prosecution history estoppel can be used against a patentee in two slightly different ways, loss of claim scope through express or implied disavowal, and loss of claim scope by elimination of the doctrine of equivalents.