722
OCTOBER TERM, 2001
Syllabus
certiorari to the united states court of appeals for the federal circuit
No. 00-1543. Argued January 8, 2002—Decided May 28, 2002
Petitioner Festo Corporation owns two patents for an industrial device.
When the patent examiner rejected the initial application for the first patent because of defects in description, 35 U. S. C. § 112, the application was amended to add the new limitations that the device would contain a pair of one-way sealing rings and that its outer sleeve would be made of a magnetizable material. The second patent was also amended during a reexamination proceeding to add the sealing rings limitation. After Festo began selling its device, respondents (hereinafter SMC) entered the market with a similar device that uses one two-way sealing ring and a nonmagnetizable sleeve. Festo filed suit, claiming that SMC's device is so similar that it infringes Festo's patents under the doctrine of equivalents. The District Court ruled for Festo, rejecting SMC's argument that the prosecution history estopped Festo from saying that SMC's device is equivalent. A Federal Circuit panel initially affirmed, but this Court granted certiorari, vacated, and remanded in light of Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U. S. 17, 29, which had acknowledged that competitors may rely on the prosecution history to estop the patentee from recapturing subject matter surrendered by amendment as a condition of obtaining the patent. On remand, the en banc Federal Circuit reversed, holding that prosecution history estoppel applied. The court ruled that estoppel arises from any amendment that narrows a claim to comply with the Patent Act, not only from amendments made to avoid the prior art, as the District Court had held. The Federal Circuit also held that, when estoppel applies, it bars any claim of equivalence for the element that was amended. The court acknowledged that, under its prior cases, prosecution history estoppel constituted a flexible bar, foreclosing some, but not all, claims of equivalence, depending on the purpose of the amendment and the alterations in the text. However, the court overruled its precedents on the ground that their case-by-case approach had proved unworkable.
Held: Prosecution history estoppel may apply to any claim amendment made to satisfy the Patent Act's requirements, not just to amendments made to avoid the prior art, but estoppel need not bar suit against every equivalent to the amended claim element. Pp. 730-742.
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