Prosecution history estoppel

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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.

The defining case on prosecution estoppel in the United states is Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co..

[edit] Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. (Court of Appeals for the Federal Circuit Holding)

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 equivalency for certain elements of his claim in instances where, during his patent prosecution he files:

1. an amendment that narrows the scope of a claim for any reason related to the statutory requirements for a patent will give rise to a complete bar with respect to the amended claim element;
2. a "voluntary" claim amendment that narrows the scope of the claim for a reason related to the statutory requirements for a patent will give rise to prosecution history estoppel as to the amended claim element; and
3. an amendment and fails to explain the reasons for the amendment during prosecution of his patent.

[edit] Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. (Supreme Court reversal)

In its holding, the Supreme Court, citing the instruction in Warner-Jenkinson "that courts must be cautious before adopting changes that disrupt the settled expectations of the inventing community.", overturned the complete bar issued by the Court of Appeals for the Federal District. 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 Supreme 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. The patentee must establish that the equivalent:

1. was unforeseeable at the time the claim was drafted;
2. the amendment did not surrender the particular equivalent in question; or
3. there was some reason why the patentee could not have recited the equivalent in the claim.