© 2002, Gallagher & Dawsey Co., LPA
The U.S. Supreme Court issued a landmark patent decision on May 28,
2002. They unanimously vacated a decision of the U.S. Court of Appeals
for the Federal Circuit (CAFC) in Festo Corp. v. Shoketsu Kinzoku
Kogyo Kabushiki Co. Unfortunately, few people, other than patent
attorneys, have recognized the importance of this case.
The decision has to do with the doctrine of equivalents and
prosecution history estoppel. The doctrine of equivalents is an
equitable doctrine established by the courts to protect patented
inventions. It allows a patent owner to prove infringement even when
the claims of the patent are not literally infringed. The doctrine of
equivalents prevents potential infringers from avoiding liability by
making minor changes to their device to avoid literal infringement.
The courts have also exercised their equitable powers to provide some
certainty in the scope of the doctrine of equivalents. Prosecution
history estoppel is one such limitation on the doctrine of
equivalents. Prosecution history estoppel relates to the amendments,
statements, arguments, and representations made during the prosecution
of a patent application. It essentially prevents an applicant from
attempting to argue that a narrowing statement, made during
prosecution "for any reason related to patentability" that limits the
scope of a patent, does not effect the scope of potential equivalents.
The CAFC decision had created an absolute bar to application of the
doctrine of equivalents for all patent claim elements narrowed by
amendment for reasons related to patentability during Patent &
Trademark Office (PTO) prosecution. The CAFC explicitly abandoned the
previous "flexible bar" approach that had permitted a case-by-case
assessment of the breadth of prosecution history estoppel based upon
the applicant's reasons for claim amendments.
Fortunately, the U.S. Supreme Court held that the doctrine of
equivalents may be limited by prosecution history estoppel, but
prosecution history estoppel is not a "complete bar" to the doctrine
of equivalents. The Court suggested that consideration be given to
whether the patentee "surrendered the particular equivalents at
issue." One consideration of the Court was that the CAFC decision
risked "disrupting the expectations of countless existing patent
holders" who had "no reason to believe they were conceding all
equivalents" by amending claims in past patent prosecution amendments.
The Court noted that it saw "no reason why a narrowing amendment
should be deemed to relinquish equivalents unforeseeable at the time
of the amendment and beyond a fair interpretation of what was
surrendered." It is important to note that the patentee has the burden
of proving that the narrowing amendment did not surrender the
particular equivalent in dispute.
The Supreme Court's decision in Festo should be a relief to patent
applicants and cause potential patent infringers to seriously
reconsider their actions.