The U.S. Court of Appeals for the Federal Circuit recently held that a district court erred in finding the doctrine of equivalents barred by prosecution history estoppel and in relying on unclaimed features to find a lack of equivalents, but nevertheless affirmed a grant of summary judgment because the plaintiff did not satisfy its burden to present particularized evidence of equivalents in opposition to the motion for summary judgment. AquaTex Indus., Inc. v. Techniche Solutions, Case No. 06-1407, (Feb. 27, 2007) (Dyk, J.).

This matter was previously before the Court in AquaTex Indus., Inc. v. Techniche Solutions, 419 F.3d 1374 (Fed. Cir., 2005). There, the Court held that claims 1 and 9 of U.S. Patent No. 6,371,977 were not literally infringed, but did not foreclose a finding of infringement under the doctrine of equivalents. The Court remanded for the district court to consider “whether or not each limitation of the claims in dispute, or its equivalent, is present in the accused Techniche products.” On remand, the district court granted summary judgment of non-infringement, and AquaTex appealed.

AquaTex’s patent related to multi-layered, liquid-retaining material used in evaporative cooling garments. During prosecution, AquaTex had made narrowing amendments to the claims in order to distinguish its claims from a prior art patent. The Court found that the subject matter surrendered by the narrowing amendment was directed to a completely different claim limitation than the “fiberfill batting material” at issue. Thus, the Court concluded that AquaTex surrendered no claim scope to the characteristics of the “fiberfill batting material” during prosecution and was not barred from asserting equivalents to the limitation. The Court then noted that AquaTex, as the plaintiff, was required to prove infringement under the doctrine of equivalents by a preponderance of the evidence. In particular, the Court pointed out, AquaTex was required to provide particularized testimony and linking argument to show the equivalents. The Court stated that, when the patent holder relies on the doctrine of equivalents, evidence must be presented to the fact finder through the testimony of a person skilled in the art, “typically a qualified expert, who (on a limitation-by-limitation basis) describes the claim limitations and establishes that those skilled in the art would recognize the equivalents.” The only evidence presented by AquaTex was their CEO’s testimony, which merely explained how the accused product operated. Thus, AquaTex did not address the equivalence of Techniche’s product to the “patented method on a limitation-by-limitation basis,” or the insubstantiality of the differences between the claimed invention and the accused device or process or the “function, way, result test,” as required. The Court concluded that the AquaTex’s presentation of lawyer argument and generalized testimony about the accused product were insufficient to demonstrate a genuine issue of material fact that would prevent the grant of summary judgment.

Practice Note: For a patentee to win a summary judgment motion under the doctrine of equivalents, the patentee should use testimony from an expert or one skilled in the art to specifically address equivalents on a limitation-by-limitation basis, explain the insubstantiality of the differences between the claims of the patent and the accused product, or discuss the function, way, result test.