On November 29, 2000, the Federal Circuit issued their long awaited decision relating to the application of the doctrine of Equivalents in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.
Prior to Festo, the Supreme Court in Warner Jenkinson v. Hilton Davis, 41 USPQ 2d 1865 (1997), explained that prosecution history estoppel was available to prevent a patentee from claiming Doctrine of Equivalents infringement where the patentee surrendered certain subject matter during prosecution of its patent application. In other words, patentees could not expand their claims during litigation to cover the subject matter surrendered during the patent application process.
Warner Jenkinson v. Hilton Davis further stated that prosecution history estoppel will generally arise when an amendment during prosecution is made for a substantial reason related to patentability and that there is a rebuttable presumption that an amendment to a claim was made for reasons of patentability where the record does not reveal the reason for the amendment.
This raised questions as to what constitutes an amendment made for substantial reasons of patentability and what would be the effect of such amendment.
The Festo case answered these questions as follows:
1. Any amendment to a claim made for a substantial reason related to patentability creates prosecution history estoppel. Some prior cases had suggested that only amendments to overcome the prior art constitute amendments made for a substantial reason related to patentability. Festo makes it clear that it is not necessary for an amendment to be made to overcome prior art in order to create estoppel. Thus, for example, narrowing amendments to overcome or avoid rejections under 35 U.S.C. 101 or 112 can be viewed as being made for a substantial reason related to patentability and hence can create estoppel.
2. Festo further held that a voluntary claim amendment can create estoppel on the same basis as an amendment required by an examiner or made in response to a rejection.
3. Some previous decisions had held that if an amendment to a claim element creates estoppel, it still may be entitled to some range of equivalents. However, Festo made clear that there is no range of equivalents for a claim element subject to prosecution history estoppel.
4. In the case where there is no explanation for an amendment to a claim element, as stated above, it is presumed that the amendment was made for a substantial reason relating to patentability. In this case, a question arises as to what range of equivalents would be granted for such amended claim element. However, Festo held that no range of equivalents would be granted in such case.
The Festo decision should be of assistance to an accused infringer in a close case where there is an issue of prosecution history estoppel based on amendments made during prosecution and particularly where the reason for such amendment is not apparent from the record.
The Festo decision will also have an impact on the way patent applications are prosecuted, since every amendment, whether voluntary or not and whether or not made to overcome the prior art, can potentially give rise to prosecution history estoppel.
If you have any questions concerning this decision, or its impact on present or previous infringement matters, please let us know.
