In its recent decision in Focus Products Group International, LLC v. Kartri Sales Co., Inc., the U.S. Court of Appeals for the Federal Circuit vacated the district court’s summary judgment of infringement on two patents and reversed its infringement finding on a third patent. The court held that the district court erred in both claim construction and infringement analysis by failing to properly recognize subject matter that had been surrendered during patent prosecution. This surrender was critical because the broad claim language otherwise covered the accused product configuration found to infringe by the district court.

A patent’s claim scope may be narrowed based on prosecution history only when there is a “clear and unmistakable” disclaimer sufficient to overcome the strong presumption that claim terms carry their full ordinary meaning. In practice, this is a demanding standard, and even arguments that successfully overcome prior art rejections often fall short of establishing such a disclaimer.

The accused product in the Focus Products case was a shower-curtain ring with a flat top edge. The Federal Circuit, relying on repeated statements by the examiner, concluded that the claims as originally presented encompassed two types of rings: one with a raised portion and another with a “flat top edge.” The patentee elected to withdraw claims covering rings with a flat top edge and did not dispute the examiner’s characterization. In the Notice of Allowance, the examiner again stated that “flat top edge” rings were outside the elected claim scope and invited the applicant to contest that understanding—yet the applicant did not do so.

Case law on prosecution disclaimer generally requires that an applicant surrender subject matter that would otherwise fall within the claim scope, and courts have often cautioned against finding disclaimer based solely on examiner statements to which the applicant did not respond. In Focus Products, however, the Federal Circuit concluded that the applicant effectively agreed with the examiner’s exclusion of rings with a flat top edge by acting in a manner consistent with that characterization.

Because the patentee accepted the narrowing of claim scope during prosecution, it could not later assert in litigation that the claims encompass ring structures with flat top edges, even though such structures would ordinarily fall within the claims’ plain meaning.

The Federal Circuit’s ruling carries two significant implications.
First, it confirms that a prosecution disclaimer need not arise from explicit and unequivocal statements by the applicant; it may instead be inferred when the applicant fails to dispute the examiner’s characterization and takes actions consistent with it.

Second, the decision indicates a relaxation of the stringent standard traditionally applied to finding prosecution disclaimer. Historically, even detailed arguments distinguishing prior art have often been deemed insufficiently “clear and unmistakable.” By contrast, the court here found disclaimer where the applicant remained silent but behaved in a manner aligned with the examiner’s stated interpretation.

Source:https://ipr.mofcom.gov.cn/article/gjxw/gbhj/bmz/mg/202511/1993889.html