Festo Redux: A Practioner´s Guide

Few patent law decisions in recent memory have generated as much debate as the Federal Circuit’s en banc decision in 2000 in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 234 F.3d 558 (Fed. Cir. 2000). The Federal Circuit held that the need for certainty and predictability in construing patent claims mandated that 1) prosecution history estoppel applies to all claim amendments made for a substantial reason relating to patentability, including amendments made to overcome non-prior art rejections, and 2) absolutely no range equivalence could be afforded to any such amended claim limitation. Immediately following the decision, most observers correctly predicted that the case was headed for Supreme Court review. After the Supreme Court's ruling in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., the patentee still has to overcome two hurdles in order to be successful in asserting equivalence of an amended claim limitation, but the second hurdle is no longer absolute and