High Court Declines to Weigh in on Doctrine of Equivalents Inquiry

The U.S. Supreme Court on Monday declined to grant a number of IP petitions, including one in which a divided panel of the U.S. Court of Appeals for the Federal Circuit (CAFC) ruled in October 2024 that NexStep, Inc. failed to prove Comcast Cable Communications had infringed its patents under the doctrine of equivalents.

NexStep owns U.S. Patent Nos. 8,885,802 (’802 patent) and 8,280,009 (’009 patent), which generally cover voice communications technology. The U.S. District Court for the District of Delaware entered summary judgment of non-infringement on the ‘802 patent based on the adopted claim construction of the term “VoIP” but denied Comcast’s motion for summary judgment of patent eligibility on the ’009 patent. A jury then entered a verdict that the ‘009 patent claims were infringed under the doctrine of equivalents but that they were not literally infringed. However, the district court set aside this verdict, granting judgment as a matter of law (JMOL) of non-infringement on the ‘009 patent due to a lack of evidence to support the jury’s finding.

Chiefly, the district court said that the testimony of NexStep’s expert, Dr. Ted Selker, “was too conclusory to sustain the verdict.” The court referred to portions of the testimony as “word salad” and said that it “lacked the specificity and analysis required by [the CAFC’s] precedent.” The court ultimately entered final judgment of non-infringement on both patents and issued a summary judgment ruling rejecting Comcast’s affirmative defense that the ’009 patent is ineligible under 35 U.S.C. § 101.

On appeal, the CAFC said the district court was correct because NexStep failed to comply with the “specific evidentiary requirements necessary to prove infringement under the doctrine of equivalents.” In particular, “both the Supreme Court and this court have made clear that the evidence of equivalents must be from the perspective of someone skilled in the art, for example through testimony of experts or others versed in the technology; by documents, including texts and treatises; and, of course, by the disclosures of the prior art,” said the majority opinion, quoting AquaTex Indus., Inc. v. Techniche Sols., 479 F.3d 1320, 1329 (Fed. Cir. 2007).

Furthermore, NexStep failed to provide the “particularized testimony and linking argument” required under the precedent. Dr. Selker’s brief testimony on the doctrine of equivalents evidence was insufficient, said the majority. First, the testimony failed “to explicitly identify the alleged equivalent”; second, it “failed to provide a ‘meaningful explanation of why’ the element or elements from the accused product or process are equivalent to the claimed limitation for each part of the ‘function-way-result test’”; his testimony amounted to “word salad” when attempting to explain “why several button presses perform the claimed method in the same way as the claimed single action”; and agreed with the district court that Selker’s testimony on the “result” prong of the function-way-result test was “untethered from the claim language” and “amounts to little more than ‘generalized testimony as to the overall similarity between the claims and the accused infringer’s product.’” The opinion explained:

“While our precedent doesn’t necessarily require an expert’s testimony to be an ipsis verbis recitation of the claim, Dr. Selker’s identified result is also too generalized, unclear, and unconnected to the claimed invention.”

The petition filed by NexStep in April of 2025 presented the question: “Whether a patentee must in every case present ‘particularized testimony and linking argument’ to establish infringement under the doctrine of equivalents.” NexStep argued that “[p]atents would provide little protection if confined to the strict, literal terms of their claims; ‘[o]utright and forthright duplication is a dull and very rare type of infringement,’ and ‘[t]o prohibit no other would place the inventor at the mercy of verbalism.’”

In the Federal Circuit decision, Judge Reyna dissented in part, saying “[t]he majority concocts a rigid new rule that in all cases a patentee must present expert opinion testimony to prove infringement under the doctrine of equivalents.” Reyna added that the majority opinion “analyzes NexStep’s evidence of infringement under the doctrine of equivalents in a vacuum and fails to adhere to the substantial evidence standard of review.” He concluded:

“I believe the majority invades the province of the jury by overturning a reasonable verdict that is supported by substantial evidence in this case and by imposing an unnecessary new rule in all future doctrine of equivalents cases to come.”