NexStep, Inc. v. Comcast Cable Communications, LLC

Under the “doctrine of equivalents,” a product that does not literally infringe the express terms of a patent claim may nonetheless infringe if there is equivalence between the elements of the accused product and those of the patented invention. This Court has long held that equivalence “is not the prisoner of a formula” and that proof of equivalence “can be made in any form.” Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 609 (1950). In the decision below, a divided panel of the Federal Circuit set aside a jury’s verdict of equivalence. The majority did so on the ground that the patentee’s expert failed to present “particularized testimony and linking argument”—a categorical, judicially created requirement that the Federal Circuit imposes on all patentees seeking to prove equivalence. The question presented is: Whether a patentee must in every case present “particularized testimony and linking argument” to establish infringement under the doctrine of equivalents. (I)