OCTOBER TERM, 1996
Syllabus
certiorari to the united states court of appeals for the federal circuit
No. 95-728. Argued October 15, 1996—Decided March 3, 1997
Petitioner and respondent both manufacture dyes from which impurities must be removed. Respondent's " '746 patent," which issued in 1985, discloses an improved purification process involving the "ultrafiltration" of dye through a porous membrane at pH levels between 6.0 and 9.0. The inventors so limited their claim's pH element during patent prosecution after the patent examiner objected because of a perceived overlap with the earlier "Booth" patent, which disclosed an ultrafiltration process operating at a pH above 9.0. In 1986, petitioner developed its own ultrafiltration process, which operated at a pH level of 5.0. Respondent sued for infringement of the '746 patent, relying solely on the "doctrine of equivalents," under which a product or process that does not literally infringe upon the express terms of a patent claim may nonetheless be found to infringe if there is "equivalence" between the elements of the accused product or process and the claimed elements of the patented invention. Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U. S. 605, 609. Over petitioner's objections that this is an equitable doctrine and is to be applied by the court, the equivalence issue was included among those sent to the jury, which found, inter alia, that petitioner infringed upon the '746 patent. The District Court, among its rulings, entered a permanent injunction against petitioner. The en banc Federal Circuit affirmed, holding that the doctrine of equivalents continues to exist, that the question of equivalence is for the jury to decide, and that the jury had substantial evidence from which to conclude that petitioner's process was not substantially different from the process disclosed in the '746 patent.
Held: 1. The Court adheres to the doctrine of equivalents. Pp. 24-30. (a) In Graver Tank, supra, at 609, the Court, inter alia, described some of the considerations that go into applying the doctrine, such as the patent's context, the prior art, and the particular circumstances of the case, including the purpose for which an ingredient is used in the patent, the qualities it has when combined with the other ingredients, the function it is intended to perform, and whether persons reasonably
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