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New challenge for patent attorneys

A recent court decision could radically change the manner in which patent applications are prosecuted through the U.S. Patent and Trademark Office. The Court of Appeals for the Federal Circuit has severely limited the application of the doctrine of equivalents to the interpretation of patent claims. Specifically, the court held that whenever a patent claim is narrowed for any reason related to “patentability”, then prosecution history estoppel (see below) may be found with respect to the amended claim element. Even voluntary or unexplained claim amendments will give rise to the prosecution history estoppel effect. The court held that when such a narrowing claim amendment creates prosecution history estoppel, no range of equivalents is available for the amended claim element.

The case of Festo Corp. v Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., a/k/a SMC Corp., and SMC Pneumatics Inc., 2000 WL 1753646 (Fed. Cir. [Mass.] No. 95-1066, Nov 29, 2000) involved two patents covering a magnetically coupled rodless cylinder. The jury found that SMC infringed the patent claims under the doctrine of equivalents. The Federal Circuit found that, because the scope of the asserted claims had been narrowed by amendment, the doctrine of equivalents could not be used to determine the scope of the claims and thus it reversed the trial court’s infringement finding.

The doctrine of equivalents is used when there is no literal infringement of a patent claim. Rather, the accused infringer has tried to avoid liability by making only insubstantial changes to the claimed invention and thus unfairly obtaining the benefit of the invention. However, the doctrine of equivalents is limited by prosecution history, which consists of statements and claim amendments made during the prosecution of the patent application in the patent office. Prosecution history estoppel prevents a patentee from later asserting that the scope of a patent claim, under the doctrine of equivalents, includes subject matter that was given up during prosecution.

The Federal Circuit held that an amendment that narrows the scope of a claim for any reason related to patentability will create prosecution history estoppel with respect to that amended claim element. Finally, the Federal Circuit held that whenever prosecution history estoppel is present, no range of equivalents is available for the amended claim element.

The courts had previously applied prosecution history estoppel in a flexible manner to narrow claim scope. Typically, prosecution history estoppel was relevant only when claim amendments were made to overcome prior art. Under the Festo approach, amendments that correct formality matters in a claim and also narrow the claim will create the estoppel, and therefore bar any broadening application of the doctrine of equivalents to the narrowed claim.

If the court’s ruling is left unchanged by an expected appeal to the U.S. Supreme Court, a premium will be placed on obtaining patents with a bare minimum of claim amendments. An inventor might consider initially filing very narrow claims to avoid any prior art in hopes of obtaining allowance of the claims as filed; broader claims could be prosecuted in later continuation applications. There may be more personal interviews with the patent examiner because few comments regarding the interview are entered into the file. Numerous other creative approaches will likely develop over time to avoid the effect of the court’s ruling and to obtain the broadest possible patent coverage for one’s inventive efforts.

Samuel P. Burkholder is an intellectual property attorney with Pillsbury Winthrop LLP in Washington, DC. An electronic copy of the Federal Circuit opinion can be obtained by contacting the author at sam.burkholder@pillsburywinthrop.com.