Issue 85 | June 17, 2003
Federal Circuit Applies Festo Decision
 In its first published opinion to apply the Supreme Court’s decision on prosecution history estoppel from Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. Ltd, the Federal Circuit held on June 2, 2003, in Pioneer Magnetics, Inc. v. Micro Linear Corp., that the patentee did not overcome the presumption that it had surrendered the equivalent in question when amending "multiplier" to "switching analog multiplier."

In reaching the application of the Festo standard, the court first concluded that there was no dispute that the amendment narrowed the scope of the claim. The court then cited Warner Jenkinson Co., Inc. v. Hilton Davis Chemical Co. for the proposition that there is presumption that there was a substantial reason related to patentability for the amendment unless the patent holder can prove otherwise. In this case, the appeals court was not persuaded that the amendment was made through "sheer inadvertence" even though there was (1) a supporting declaration from the prosecuting attorney, (2) remarks with the amendment stating that the amended claim included the limitations of former dependent claims without the limitation, and (3) a similar "switching" limitation in an issued dependent claim. In fact, the court refused to consider the declaration and specifically noted that "the mere fact that an amendment is voluntary does not shield it from prosecution history estoppel." It then went on to conduct its own examination of the prosecution history in order to determine that the amendment was made to avoid the prior art and was therefore related to patentability.

In only the last paragraph of its decision did the court address rebuttability of the presumption under Festo when "[t]he equivalent [was] unforeseeable at the time of the application; the rationale underlying the amendment [bears] no more than a tangential relation to the equivalent in question; or there [was] some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question." According to the decision, since the non-switching circuit was disclosed in the cited reference, it would have been foreseeable at the time of the amendment. The amendment was not tangential to the equivalent in question because it was made to avoid the very prior art that contained the amendment. And, given the equivalent’s presence in a reference that was cited during prosecution, there could be no other reason that the patentee could not have described the substitute in question in the application. The plaintiff was therefore estopped from arguing any equivalents to the "switching analog multiplier circuit" limitation of the claims.

A copy of the decision is available on the Internet at http://www.fedcir.gov/opinions/00-1012.doc. Please feel free to contact the authors, Benjie Balser and Bill Heinze, at Thomas, Kayden, Horstemeyer & Risley in Atlanta, Georgia USA, if you would like to know more about what effect this decision may have on your patent enforcement program.

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