Supreme Court rules on Festo

Patent holders worldwide have been nervously awaiting the result of a 13-year patent-infringement battle between Festo Corporation and Shoketsu Kinzoku Kogyo Kabushiki Co. (known as SMC), which has important consequences for patent-infringement protection. On 28 May 2002, the US Supreme Court unanimously decided to vacate the earlier ruling of the US Court of Appeals for the Federal Circuit, which had ruled that amendments that were made during the prosecution of a patent application effectively made the protection of the patent under the doctrine of equivalents unavailable.

The doctrine of equivalents is designed to prevent potential patent infringers from avoiding liability by simply making insubstantial changes to a patented invention. In the Festo case, Festo held a patent for a magnetic piston, which is used in a wide range of devices, that crucially contained an amendment stating that the device would contain a pair of one-way sealing rings and that its outer sleeve would be made of a magnetizable material. When SMC entered the market with a similar device, which instead used one two-way sealing ring and a non-magnetizable sleeve, Festo filed suit. In 2000, in the latest of a long line of cases and appeals, the Federal Court ruled that, in the process of amending the claims of their patent, Festo had relinquished the protection afforded by the doctrine of equivalents. This applied to all equivalents, not just to those equivalent products that related to the amended claim, and not just to those amendments that were meant to narrow the claim to avoid prior art. This decision reverberated through patent communities, because amendments to patent applications are commonplace, and the decision therefore threatened to render the doctrine of equivalents so narrow as to be useless for enforcing the 1.2 million patents in existence, as well as many others still under review.

Although the latest decision, written by Justice Anthony Kennedy, vacates the Federal Circuit's previous ruling, it does not offer patent applicants carte blanche to make amendments during the prosecution process. Kennedy wrote that, in a return to the Warner Jenkinson ruling of 1997, the Federal Courts can presume that patentees abandon the right to protection under the doctrine of equivalents with respect to any elements that are contained in an amendment. However, patentees can rebut this presumption and claim equivalent protection in such cases if they can prove that the equivalent could not reasonably have been foreseen at the time of drafting the amendment. In the case of Festo Corp v. SMC, the Supreme Court have left the decision of whether Festo can rebut the presumption to the Federal Circuit Court. WEB SITES US Department of Justice Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.Supreme Court of the United States Supreme Court's decision in Festo v. SMCLegal Information Institute Supreme Court Collection Supreme Court's decision in Warner Jenkinson