Outside Counsel

In a unanimous opinion issued Tuesday, May 28, 2002, the U.S.States Supreme Court vacated a controversial opinion by the Court of Appeals for the Federal Circuit relating to the scope of patent protection and more specifically to prosecution history estoppel and the doctrine of equivalents, two patent law concepts at issue in most patent infringement law suits. The Court rejected the Federal Circuit’s per se rule that prosecution history estoppel acts as a complete bar to any range of equivalents, contending that such a significant change in the law must be made by Congress, not the courts. The Court ruled that although narrowing amendments made to satisfy any requirement of the Patent Act may give rise to an estoppel, the estoppel does not necessarily bar suit against every equivalent to the amended claim element. The ruling in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., was eagerly anticipated by the patent bar as many had argued that the Court of Appeals decision cast doubt on the breadth of approximately 1.2 million unexpired U.S. patents.

Background