Festo Corp. V. Shoketsu Kinzoku Kogyo Kabushiki Co. - Court's Decision

Court's Decision

The Supreme Court vacated the ruling made by the Federal Circuit, holding that such amendments do not create an absolute bar, but instead must be examined in light of the reason for the change. In the unanimous opinion, Justice Kennedy explained that it was not whether prosecution history estoppel applied to amendments, but to what extent the amendment surrendered coverage of the claim. If the change was made to clarify a translation, for example, the inventor should suffer no reduction in rights. But if the change was made to keep the patent from overlapping with another patent, then the applicant will be presumed to have given up the right to complain about anything broader than the patent claim itself.

In particular, the Court held that patentee's decision to narrow claims through amendment in order to comply with the Patent Act automatically assumes surrender of the territory between the original claim and the amended claim, i.e., a presumption of surrendering all equivalents for the particular claim limitation that was narrowed by the amendment. The Court thus placed the burden on the applicant as to showing what equivalents were not surrendered.

Still, the Court conceded, however, that there are some cases where the amendment cannot be viewed as surrendering a particular equivalent. "The equivalent may have been unforeseeable at the time of the application; the rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question; or there may be some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question. In those cases the patentee can overcome the presumption that prosecution history estoppel bars a finding of equivalence."