RECONSIDERING THE INTERCHANGEABILITY FACTOR UNDER THE DOCTRINE OF EQUIVALENTS

The United States Supreme Court has indicated that the doctrine of equivalents essentially prohibits the practice a fraud on a patent. To permit imitation of a patented invention that does not copy every literal detail is to deem patent-grant protection hollow and useless. This deprives the inventor of the benefit of his invention and fosters invention concealment rather than disclosure, which is one of the primary purposes of the patent system. An important factor in determining equivalency is to assess whether persons skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was. Therefore, the Federal Circuit often cites interchangeability as a factor that may influence an equivalency decision. However, the effect of the interchangeability approach is ambiguous. This article reviews the Supreme Court and Federal Circuit decisions on the interchangeability factor, and provides a critical analysis. Because of the uncertainty of interchangeability, the article proposes to reconsider the effect of interchangeability factor under the doctrine of equivalents.