Festo XIII: Federal Circuit Further Circumscribes Doctrine of Equivalents

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.

Commentary:
Dewey Ballantine: Federal Circuit Elucidates 'Foreseeability' Component of Equivalents Test
Sutherland Asbill & Brennan: Making the Unforeseeable, Foreseeable

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.

Newman, J. dissented, arguing that:

[the] foreseeable result [of the majority opinion] is to deprive amended claims of access to the doctrine of equivalents.

Slip Op. at 2 (Newman, J., dissenting).

The doctrine of equivalents allows a patentee to prove infringement even when there are minor differences between the patented apparatus and the allegedly infringing apparatus. A patentee may prospectively deprive herself of access to the doctrine of equivalents through a doctrine known as prosecution history estoppel, by amending her patent claims during the prosecution of her patent application to narrow the scope of her claims in such a way as to exclude the infringing apparatus. In turn, there are three exceptions to prosecution history estoppel:

(1) the equivalent was "unforeseeable at the time of the application," (2) "the rationale underlying the amendment [bears] no more than a tangential relation to the equivalent in question," or (3) . . . "some other reason suggest[s] that the patentee could not reasonably be expected to have described the insubstantial substitute in question."

Slip Op. at 9 (quoting Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 740-41 (2001)).

Festo XIII covers the foreseeability exception; specifically, it addresses the question of whether an equivalent known at the time of the application, but not known to be used as an equivalent to the patented apparatus, was foreseeable.