Prosecution history estoppel, also known as file-wrapper estoppel, is a term used to indicate that a person who has filed a patent application, and then makes narrowing amendments to the application to accommodate the patent law, may be precluded from invoking the doctrine of equivalents to broaden the scope of their claims to cover subject matter ceded by the amendments.
[4] The German Federal Court of Justice ruled in 2002 that "issues derived from prosecution history cannot be taken into account in the assessment of the scope of protection of a patent, even with regard to the requirement of legal certainty".
[1][5] More than a decade later, the Federal Court of Justice ruled[6] on 14 June 2016 that statements made during prosecution may indicate how the skilled person construes a patent.
The Irish Supreme Court has ruled that "evidence from the file which reflects the views of the patentee as to the construction of the claims is inadmissible".
This complete bar rule completely prohibited a patent owner from asserting the doctrine of equivalents for certain elements of her claim in instances where, during her patent prosecution she files: The United States Supreme Court in their opinion Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U. S. 722 (2002), citing the instruction in Warner-Jenkinson Company, Inc. v. Hilton Davis Chemical Co., finding that "courts must be cautious before adopting changes that disrupt the settled expectations of the inventing community", overturned the complete bar issued by the Federal Circuit.