The doctrine of equivalents is not new in the U.S. The doctrine has, for many years, protected patent claims beyond their literal scope. But as a result of the Federal Circuit’s recent ruling in Sextant Avionique, S.A. v. Analog Devices, Inc., [FOOTNOTE 1]many holders of U.S. patents will find it more difficult to obtain protection under the doctrine of equivalents.

The doctrine of equivalents protects patented inventions against activities that “perform substantially the same overall function or work in substantially the same way” to produce the same result. [FOOTNOTE 2]The Sextantruling concerns a limit the U.S. courts have placed on this doctrine: Amendments to patent claims and arguments presented during patent prosecution can create “prosecution history estoppel.” Such estoppel arises when the claims were amended for a reason “related to patentability,” [FOOTNOTE 3]and the resulting estoppel excludes “from the range of equivalents subject matter surrendered during prosecution of the application.” [FOOTNOTE 4]