ASHINGTON, June 18 — Accepting an important patent case, the Supreme Court agreed today to review an appellate decision that according to an unusually broad array of industry, educational and intellectual property groups has seriously undercut the value of many current patents and patent applications.

In a ruling last November widely known as the Festo decision, the United States Court of Appeals for the Federal Circuit reinterpreted a major doctrine of patent law in a way that makes patents harder to defend and easier to infringe, according to many patent law experts.

The Federal Circuit, which sits in Washington, is a specialized court with nationwide jurisdiction over patent appeals. For that reason, its 8-to-4 ruling in a 13-year-old dispute between two manufacturers of magnetic cylinders had nationwide ramifications. That caused patent holders in a wide range of fields to rally around the Festo Corporation of Hauppauge, N.Y., the American subsidiary of a German company, Festo A.G., in seeking Supreme Court review.

In its opinion, the full appeals court overturned an earlier opinion by a three-judge panel and found that a Japanese competitor had not infringed Festo's cylinder technology. The court's majority reached that conclusion based on a new interpretation of a decades-old rule of patent law known as the doctrine of equivalents.

Under the doctrine of equivalents, a device that is not an exact copy can still be found to infringe a patent if it varies from the patented device only in insubstantial details and is therefore equivalent to it. This doctrine is extremely valuable to patent holders, because it prevents competitors from avoiding infringement liability simply by making minor changes in what would otherwise be exact copies.

In the Festo decision, the Federal Circuit limited the doctrine of equivalents by holding that it was not available for any patent claim that a patent applicant or holder had amended during the process of obtaining the patent. The court invoked a doctrine known as "prosecution history estoppel," a removal of protection for any aspect of the patent that was limited or changed during the normal back-and-forth between the applicant and the Patent and Trademark Office.

The new rule replaced the former case-by-case assessment of a patent holder's waiver of protection for particular aspects of a patent. "A complete bar, unlike a flexible bar, thus lends certainty to the process of determining the scope of protection afforded by a patent," the Federal Circuit said in explaining its decision.

Because nearly all patent applications are amended during a process that typically lasts from 18 months to three years, the ruling was highly unsettling to the intellectual property community.

The application process is "basically a dance back and forth" between the applicant and the patent office, said Scott H. Blackman, a patent lawyer here who filed a brief on behalf of the Association of Patent Law Firms in which he urged the justices to hear Festo's appeal. In an interview, he said it was extremely common for the scope of a patent to be scaled back during the process, on the widely held theory among patent lawyers that if an application was accepted without any amendments, "you probably didn't ask for enough."

Other groups supporting the appeal are the United States Chamber of Commerce, the American Intellectual Property Law Association and a group of universities and research institutions including the Massachusetts Institute of Technology, Cold Spring Harbor Laboratory and the M. D. Anderson Cancer Center.

Festo's appeal, filed by Robert H. Bork, the former appeals court judge, told the Supreme Court that the ruling would have an acutely "destabilizing" effect on 1.2 million existing patents, with a "significant diminution" of patent holders' property rights.

The company said the decision "abolishes most of the protection afforded by the United States patent laws." It added, "No copyist need now fear the doctrine of equivalents and only a fool would fail to make an insubstantial change to avoid the literal terms of a patent claim."

The defendant company, Shoketsu Kinzoku Kogyo Kabushiki, which does business in the United States as the SMC Corporation , told the court that what it called the "doctrinal refinement" of the appeals court's ruling was "a natural and well-justified response to the harmful uncertainty that comes from too flexible a case-by-case approach."

The case, Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., No. 00- 1543, will be argued next fall in what promises to be an unusually significant Supreme Court term for patent law. In a case called J. E. M. AG Supply Inc. v. Pioneer Hi-Bred International Inc., No. 99-1996, the court is due to decide whether plants produced from seeds are eligible for patents.

Category: 2. Patent Law