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 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.
Although primarily a U.S. term, questions of whether, or the extent to which the prosecution history should be relevant for determining the extent of protection of a patent also arise outside the U.S.[1]
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The defining case on prosecution estoppel in the United states is Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co..
In November 2000, the Court of Appeals for the Federal Circuit set a complete bar rule. This complete bar rule completely prohibited a patent owner from asserting the doctrine of equivalents for certain elements of his claim in instances where, during his patent prosecution he 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., found 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. It also acknowledged that while any narrowing amendment made for a reason related to patentability could give rise to prosecution history estoppel, inventors who amended their claims under the previous case law had no reason to believe that they were conceding all equivalents of amended elements when responding to a rejection. Had they known, the Court stated, they might have appealed the rejection.
With this policy in mind, the Court stated that it preferred a presumptive bar approach to the doctrine of equivalents. This presumptive bar approach holds that where claims are amended, "the inventor is deemed to concede that the patent does not extend as far as the original claim" and the patentee has the burden of showing that the amendment does not surrender the particular equivalent. To succeed, then, the patentee must establish that:
This leading case in Canada on the issue of file wrapper estoppel, confirmed the emphatic rejection of this doctrine in Canada, as seen in previous cases, such as Lovell Manufacturing Co. v. Beatty Bros. Ltd. (1962). In Canada, no distinction is drawn in this regard between cases involving allegations of literal infringement and those involving substantive infringement. This means that the negotiations that have taken place between the patentee and the Patent Office cannot be used in order to establish a particular equivalent. Similarly, a patentee is barred from using any previous negotiations with the Patent Office in order to determine the scope of the claims of the patent (i.e. the negotiations cannot be used by the patentee or against the patentee in determining the scope of the claims within the patent).
The German Supreme Court, the Bundesgerichtshof, ruled in 2002 that "For the determination of the extent of protection of a patent, occurrences in the examination proceedings which preceded the grant in principle are irrelevant".[1][2]
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".[1][3]
The Dutch Supreme Court has effectively come to the opposite conclusion to most other countries in Europe.[1] The Dutch Supreme Court has stated that where "a third party invokes the examination file in the course of confirming the interpretation defended by him of a patent, it cannot be seen that that requirement [the reasonable doubt threshold] would force any restriction on involving public data from the examination file with the interpretation of the patent".[4]
The UK Courts have ruled that use of the examination file in aiding construction of a patent should be discouraged[5] except where that file includes "objective information about and commentary on experiments".[1][6]