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The Supreme Court unanimously held May 28, 2002 (1) that any narrowing amendment of a patent claim made in order to satisfy a requirement of the Patent Act may produce a prosecution-history estoppel precluding application of the doctrine of equivalents with respect to the claim; and (2) that the scope of such an estoppel does not automatically preclude every assertion of equivalence, but rather is limited to recovering under the doctrine of equivalents subject matter that was surrendered by the narrowing amendment. With regard to the latter issue, the Court held that the patentee bears the burden of proving that the amendment does not surrender the equivalent at issue. The Federal Circuit had imposed an absolute bar against application of the doctrine of equivalents where the claim at issue had been the subject of any narrowing amendment to secure patentability. The case is important to all businesses holding patents or operating in an industry where competitors hold patents.

Lower Court Opinion: 234 F.3d 558 (Fed. Cir. 2000).