The Doctrine of Equivalents and the Third Prong of the German Test: A Comparative Law Perspective

Abstract

This article examines the recent trend of applying and limiting the doctrine of equivalents (DOE) in U.S. and German courts. The German Federal Court of Justice (BGH) established a three-prong test for applying the DOE in Schneidermesser. In Pemetrexd, BGH’s application of the third prong – guidance by the claim – moved German DOE more in line with that of U.S. in preventing patentees from asserting DOE on disclosed but unclaimed variant means. Although prosecution history estoppel (PHE) remains a major difference between German and U.S. DOE, the Federal Circuit’s new approach to applying PHE flexibility results in a merger with the German approach in Formstein — DOE is rejected when the accused embodiment lacks novelty or an inventive step. As a result, both BGH and the Federal Circuit reached the same conclusion in the German and U.S. Pemetrexed cases: Infringement under DOE.

Keywords: patents, comparative law, doctrine of equivalents