Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd. (“SMC”)
Federal Circuit, No. 05-1492, July 5, 2007
Slip Opinion

On July 5, in the latest decision in a nearly-twenty-year saga which has cumulatively proven enormously important in defining the scope of the doctrine of equivalents, the Federal Circuit (Dyk, J.) held that an existing equivalent can be foreseeable at the time of a patentee’s amendment, even if it would have been impossible for an observer of ordinary skill in the art to foresee at the time of amendment that the equivalent would ultimately satisfy the tests for equivalence. In the court’s words:

An equivalent is foreseeable if one skilled in the art would have known that the alternative existed in the field of art as defined by the original claim scope, even if the suitability of the alternative for the particular purposes defined by the amended claim scope were unknown.

Slip Op. at 21.