Posted on Sep 15, 2010 in News | 0 comments


At the end of November 2000, the Court of Appeals for the Federal Circuit decided the now infamous Festo Case. This case stated that a narrowing amendment to any claim limitation created an absolute bar to any equivalents for that claim limitation under the doctrine of equivalents. Thus, at least in relation to a patent where claims were amended, an infringer had a free run at copying a patented invention with only minimal changes. The patentee was then limited to only literal infringement for such narrowed limitations.

Since the procedure for obtaining patents has always been to start as broad as it might be possible to obtain, and to narrow claims only as much as necessary during prosecution, this new holding effectively reduced the value of most of the one million plus unexpired patents.

On 28 May 2002, the U.S. Supreme Court reversed the Court of Appeals on that particular point. The Supreme Court stated that “The Court of Appeals ignored the guidance of Warner-Jenkinson, which instructed that courts must be cautious before adopting changes that disrupt the settled expectations of the inventing community. The Court also in Warner-Jenkinson affirmed that the doctrine of equivalents was still available to patentees and refused to abolish it, even though the Justices did enunciate restrictions. The Court went on to say that the Court of Appeals must be cognizant of the give-and-take process as an application proceeds through the Patent and Trademark Office and that any major changes in policy or procedure should be handled by Congress and not by the Courts.

It is not clear how the subject of the doctrine of equivalents will play out, because the equivalents bar has been left relatively high by the Supreme Court. However, patent owners’ reasonable explanations as to why amendments were made must be considered by courts and the absolute bar has been softened somewhat. Time will tell and as of 2013 the issue is not clear or stabilized.