IP Law Daily, PATENT NEWS—NexStep petitions High Court for review of Federal Circuit’s doctrine of equivalents evidentiary rule, (May 9, 2025)

By Saurabh Kashyap, B.A., LL.B., LL.M.

Federal Circuit’s “particularized testimony and linking argument” requirement conflicts with Supreme Court precedent and undermines the jury’s fact-finding role, the petition asserts.

NexStep, Inc. has filed a petition for a writ of certiorari with the U.S. Supreme Court, asking it to review a Federal Circuit decision that overturned a jury verdict finding Comcast Cable Communications, LLC liable for patent infringement under the doctrine of equivalents. NexStep contends that the Federal Circuit’s “particularized testimony and linking argument” requirement imposes an inflexible evidentiary burden that conflicts with Supreme Court precedent, undermines the jury’s role, and threatens to narrow the doctrine of equivalents into near-obsolescence. The petition raises important questions about the legal framework governing patent infringement by equivalents and has drawn close attention in the patent litigation community (NexStep, Inc. v. Comcast Cable Communications, LLC, Dkt. No. 24-113 (U.S. filed Apr. 30, 2025)).

Background. NexStep, a technology startup that designs solutions to streamline user interactions with electronic devices, owns U.S. Patent No. 8,280,009 (the ’009 patent). The patent covers a method of initiating technical support for home electronics through “a single action performed by a user.” In 2018, NexStep filed suit in the District of Delaware against Comcast, alleging that Comcast’s My Account App infringed the ’009 patent both literally and under the doctrine of equivalents. NexStep focused particularly on the app’s troubleshooting feature, which allows customers to launch technical support through a short series of button presses.

At trial, NexStep’s expert presented technical demonstrations and explained that although the app required multiple button presses, its operation was functionally equivalent to the claimed “single action.” NexStep relied on the “function, way, result” test articulated by the Supreme Court in Graver Tank & Manufacturing Co. v. Linde Air Products Co., 339 U.S. 605 (1950), and urged the jury to treat the My Account App’s process as a substantial equivalent of the patented method.

The jury rejected NexStep’s literal infringement claim but found Comcast liable under the doctrine of equivalents, awarding damages. Comcast moved for judgment as a matter of law, arguing that NexStep had failed to meet the Federal Circuit’s evidentiary threshold requiring “particularized testimony and linking argument” to connect each claim limitation to the accused product. The district court agreed and set aside the jury verdict, finding that NexStep’s expert had not sufficiently explained which specific button presses corresponded to each element of the claimed invention.

Federal Circuit ruling. On appeal, a divided Federal Circuit panel affirmed the district court’s ruling. The majority emphasized that patent holders seeking to prove infringement under the doctrine of equivalents must offer particularized evidence explaining why differences between the accused product and the patent claims are insubstantial. The majority relied on its precedents in VLSI Technology LLC v. Intel Corp., 87 F.4th 1332 (Fed. Cir. 2023), Texas Instruments Inc. v. Cypress Semiconductor Corp., 90 F.3d 1558 (Fed. Cir. 1996), and Lear Siegler, Inc. v. Sealy Mattress Co. of Michigan, Inc., 873 F.2d 1422 (Fed. Cir. 1989).

The appellate court found that NexStep’s expert had described the accused technology only at a general level, without sufficiently linking the app’s steps to the specific limitations of the ’009 patent or addressing each limitation under the “function, way, result” framework. The majority ruled that even where the technology is relatively simple, the legal complexity of the doctrine of equivalents requires clear and particularized expert analysis to prevent overextension of patent scope.

Dissenting opinion. Circuit Judge Jimmie Reyna dissented in part, criticizing the majority for adopting what he called a rigid and overly formalistic evidentiary rule. Reyna argued that the doctrine of equivalents was intended to be a flexible, fact-based inquiry, consistent with Graver Tank and later Supreme Court cases such as Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), and Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002). He contended that the majority’s rule undermined the jury’s fact-finding role and risked excluding valid infringement claims simply because experts fail to recite a checklist of formal “linking arguments.”

Reyna stressed that in straightforward cases, such as the button-pressing technology at issue here, jurors are capable of drawing reasonable inferences about equivalence without needing hyper-detailed expert testimony. He warned that the majority’s approach improperly elevated form over substance and would chill legitimate infringement claims under the doctrine of equivalents.

Questions presented in the petition In its Supreme Court petition, NexStep presents two questions for review: (1) Whether the Federal Circuit’s “particularized testimony and linking argument” requirement for doctrine-of-equivalents claims is consistent with Supreme Court decisions, including Graver Tank & Manufacturing Co. v. Linde Air Products Co., 339 U.S. 605 (1950), Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), and Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002); and (2) Whether the Federal Circuit’s evidentiary rule improperly invades the jury’s role as the constitutionally designated factfinder in patent infringement cases.

Arguments raised in the petition. NexStep argues that the doctrine of equivalents was developed to prevent “fraud on the patent” by ensuring that minor, insubstantial changes do not enable a competitor to avoid liability. The company contends that the Supreme Court has repeatedly emphasized the doctrine’s flexibility and fact-intensive nature, notably in Graver Tank, where the Court stressed that equivalence “is not the prisoner of a formula” and “is to be determined against the context of the patent, the prior art, and the particular circumstances of the case.”

According to NexStep, the Federal Circuit's rule requiring a formal "linking argument" and highly particularized expert testimony amounts to a rigid checklist that is inconsistent with the Supreme Court's flexible approach. The petition argues that this rule improperly elevates form over substance, particularly in cases involving relatively simple technologies that jurors can understand without exhaustive technical explanations.

NexStep further asserts that the Federal Circuit’s standard risks nullifying the doctrine of equivalents in practice by enabling courts to take equivalence questions away from juries on purely formal grounds. The company cites the Federal Circuit's own dissent in this case and decisions from other panels, warning that the particularized testimony rule has become a de facto substantive requirement, rather than a procedural safeguard.

Reliefs requested. NexStep requests that the Supreme Court: (1) grant certiorari to review the Federal Circuit’s decision and resolve the conflict between the Federal Circuit’s evidentiary rule and the Supreme Court’s doctrine-of-equivalents precedents; (2) reverse the Federal Circuit’s judgment and clarify that the doctrine of equivalents is governed by a flexible, context-sensitive analysis that does not require rigid evidentiary formalism; and (3) Remand the case for a jury determination on infringement under a corrected legal standard, restoring the jury’s role in assessing whether the accused product is substantially equivalent to the claimed invention.

NexStep also urges the Court to reaffirm that the Federal Rules of Evidence govern the admissibility and sufficiency of evidence in patent cases, and that no special heightened evidentiary burden applies simply because the doctrine of equivalents is at issue.

Broader concerns raised in the petition. Beyond its specific dispute with Comcast, NexStep frames the case as an opportunity to address what it describes as a growing erosion of the doctrine of equivalents in Federal Circuit jurisprudence. The company points to the increasing use of procedural and evidentiary barriers, such as “vitiation” rules, heightened expert requirements, and formalistic standards, which, it argues, risk collapsing the doctrine of equivalents into literal infringement analysis.

The Case is Dkt. No. 24-113.

Attorneys: Daniel N. Lerman (Kramer Levin Naftalis & Frankel LLP) for NexStep, Inc.

Companies: NexStep, Inc.; Comcast Cable Communications, LLC

News: Patent FedCirNews