On October 24, 2024, the United States Court of Appeals for the Federal Circuit issued a ruling in Nexstep, Inc. v. Comcast Cable Communications, LLC, affirming the District Court for the District of Delaware’s judgment of non-infringement regarding two patents held by Nexstep, Inc. Nexstep had asserted that Comcast’s products infringed U.S. Patent Nos. 8,885,802 and 8,280,009, which cover a remote control device with voice-over-internet-protocol (VoIP) capabilities.
The Federal Circuit’s review encompassed the district court’s claim construction, the district court’s grant of summary judgment of non-infringement of the ’802 patent, and the district court’s grant of judgment as a matter of law of non-infringement of the ’009 patent. Nexstep asserted that Comcast’s system for remote control operation infringed on the ’009 patent by performing substantially the same function in the same way as Nexstep’s patented technology. Ultimately, the Federal Circuit found that Nexstep’s arguments regarding the evidentiary support for the doctrine of equivalents were insufficient, leading it to affirm the district court’s ruling in Comcast’s favor.
Nexstep’s doctrine of equivalents argument required it to make a detailed showing, as established by Federal Circuit precedent. A critical component of this showing is the requirement for “particularized testimony and linking argument” to support equivalency for each limitation in the patent claim. Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 29 (1997); AquaTex Indus., Inc. v. Techniche Solutions, 479 F.3d 1320, 1328-29 (Fed. Cir. 2007). This standard ensures that equivalency arguments are grounded in a detailed, limitation-by-limitation comparison between the patented claim and the accused product, providing the fact-finder with a clear framework for assessing each element’s equivalency. In this case, the district court held that Nexstep failed to meet this standard, as its expert, Dr. Ted Selker, offered only generalized statements regarding similarity, which the district court described as “word salad” lacking specificity and analytical rigor. Nexstep, Inc. v. Comcast Cable Commc’ns, LLC, 2022 U.S. Dist. LEXIS 85842, at *20-*21 (D. Del. May 12, 2022).
In affirming the district court’s judgment, the Federal Circuit emphasized that “the patentee must provide particularized testimony and linking argument as to the insubstantiality of the differences between the claimed invention and the accused device.” See Nexstep, Inc. v. Comcast Cable Commc’ns, LLC, No. 2022-1815, 2024 U.S. App. LEXIS 26867, at *26 (Fed. Cir. Oct. 24, 2024). The failure to specifically identify and link each component in Comcast’s system to a corresponding limitation in the patent rendered Dr. Selker’s testimony inadequate under this standard. Id. at *41-*42.
Additionally, the Federal Circuit clarified that this requirement for particularized testimony applies uniformly to all technologies—whether complex or easily understood. The court noted that the doctrine of equivalents requires the same level of evidentiary detail in simple cases as in complex cases to prevent the jury from making unsupported leaps in its findings. Id. at *49.
Accordingly, the Federal Circuit upheld the district court’s entry of judgment as a matter of law, concluding that Nexstep had not provided sufficient evidence to support its doctrine of equivalents claim under established legal standards. Id.
This ruling underscores the need for patent holders to craft doctrine of equivalents contentions with the same rigor as literal infringement analyses. To succeed, practitioners must provide “particularized testimony and linking argument” at a highly granular level, demonstrating a limitation-by-limitation comparison between the accused product and the patented claims. Without the same detailed, element-by-element scrutiny applied to literal infringement claims, patent holders risk having their doctrine of equivalents assertions deemed insufficient. Additionally, the Federal Circuit’s emphasis on a universal showing for both complex and simple technologies places additional pressure on patent holders to prepare doctrine of equivalents contentions meticulously. By requiring the same level of particularized testimony regardless of a technology’s complexity, the court has set a high, consistent bar for all equivalency claims. Ultimately, Nexstep reaffirms the Federal Circuit’s stance that the doctrine of equivalents requires as much analytical depth as literal infringement—regardless of the technology involved.