Harmonizing Prosecution History Estoppel and the Doctrine of Equivalents in Patent Infringement Actions

The patent law's doctrines of prosecution history estoppel and equivalents have come head on in the Court of Appeals for the Federal District's decision Festo Corporation v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd. ("Festo"). The case, currently before the United States Supreme Court, involves issues relating to the scope of invention that should be afforded to patents in patent infringement actions. This decision threatens to shift dramatically and unjustifiably the balance struck by patent law and practice between patentees and alleged infringers in favor of infringers regarding the interpretation of patents. That is, the Festo decision, by expanding the applicability of prosecution history estoppel in patent infringement actions, substantially curtails a patentee's bases for obtaining a judicial finding of infringement under the doctrine of equivalents. In Festo, the Federal Circuit departed from United States Supreme Court precedent and its own longstanding and well-established practice of using a "flexible bar" approach to determine whether a patentee was estopped under the doctrine of prosecution history estoppel from asserting infringement under the doctrine of equivalents. The Festo Court adopted a much more stringent "complete bar" approach to determine whether prosecution history estoppel estops a patentee from asserting equivalents infringement. This "complete bar" approach limits substantially a patentee's ability to obtain a finding of infringement under the doctrine of equivalents. This article proposes that the Federal Circuit has not justified in abandoning its own precedent and Supreme Court precedent when it discarded the "flexible bar" approach in favor of the "complete bar" approach. I propose that Supreme Court and Federal Circuit precedent compel the conclusion that what the Festo Court has denominated as the "complete bar" approach is just an application of the "flexible bar" approach to a particular fact pattern. The Festo decision should be reversed by the Supreme Court and the "flexible bar" approach to prosecution history estoppel should be reinstated. I conclude that the Court of Appeals for the Federal Circuit had little or no basis for abandoning the "flexible bar" approach in favor of a nonexistent "complete bar" approach when making prosecution history estoppel determinations. The balance that has existed for many years between prosecution history estoppel and the doctrine of equivalents has served the United States patent system well and should not be altered. The Federal Circuit provided no sensible reason to alter this balance.