In two recent cases, Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), and Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002), the Supreme Court unanimously approved of the modern doctrine of equivalents articulated in Graver Tank & Manufacturing Co. v. Linde Air Products Co., 339 U.S. 605 (1950). The Court also extended equivalents protection to later-arising technologies and imperfectly reconciled the modern doctrine with the doctrine of prosecution history estoppel for amended claims. The Court's new doctrine conflicts with historic implied-disclaimer standards. The U.S. Court of Appeals for the Federal Circuit has further revised the Supreme Court's reconciliation of these doctrines for amended claims, and has adopted different standards for claim construction and argument estoppel that conflict with the Court's new Festo standards.This article - forthcoming in the Federal Circuit Bar Journal - describes how the modern doctrine of equivalents operates and how it relates to prosecution history estoppel in light of the recent Supreme Court and Federal Circuit decisions. The article also discusses the differences between dedication of disclosed subject matter and implied disclaimer of equivalents and describes the conflicts that have been created among the claim scope, estoppel, and implied disclaimer doctrines. In particular, the article explains how the modern doctrine extends patent protection to later-arising equivalent technologies that the applicant could not have claimed and thus to which the modern doctrine should not apply.
Joshua D. Sarnoff, The Doctrine of Equivalents and Claiming the Future After Festo, 14 FED. CIR. B.J. 403 (2005)