IP Alerts

Federal Circuit Emphasizes the Need for Expert Witness Testimony to Unambiguously Map Claim Limitations to an Accused System

October 1, 2025

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On September 24, in Finesse Wireless LLC v. AT&T Mobility LLC, Nokia of America Corporation (AT&T), the Federal Circuit reversed the denial of judgment as a matter of law (JMOL) and vacated the damages award of $166 million against AT&T. The decision cited self-contradictory testimony by Finesse’s expert witness.

The Federal Circuit reviewed the jury’s findings of infringement of two US patents owned by Finesse: 7,346,134 and 9,548,775 (‘134 and ’775). Both patents involve reducing interference signals in radios.

Relying on a Nokia technical document in trying to demonstrate that the accused radios infringe the asserted claims of the ‘134 patent, Finesse’s expert witness, Dr. Wells, repeatedly pointed to two elements on a schematic as corresponding to “signals of interest” and “interference generating signals.” After later being made aware that he had misinterpreted the Nokia document’s legend, Finesse’s expert “pivoted” to reference different elements within the Nokia document. The Federal Circuit found this “pivot” contradictory and flawed, resulting in “confusing and unclear” testimony, and thus unable to support the jury’s determination of infringement.

In attempts to show infringement of the ‘775 patent, Dr. Wells again relied on the Nokia document. The claim language at issue was “three signals,” whether they were separately identifiable or unique, and digitally multiplied in seven multiplications. While the Federal Circuit did not agree with AT&T that Finesse surrendered claim scope when it amended “two or three signals” to “three signals,” they did agree that the Nokia document does not show that the accused radios perform the seven claimed multiplications. Dr. Wells testified that there were three separately identifiable signals with only three distinct multiplications and failed to explain how the accused radios perform the seven claimed multiplications.

Based on the inconsistent testimony by Finesse’s expert witness and the failure to adequately map how the three disclosed multiplications corresponded to all seven claimed multiplications, the Federal Circuit determined that the jury’s infringement verdict against both patents was not supported by substantial evidence. Moreover, the court reversed the district court’s denial of JMOL and further vacated the damages award.

This decision underscores the Federal Circuit’s increasing expectations for clarity and consistency in expert testimony and the mapping of claim limitations to the accused system in patent trials. Such accurate testimony is crucial for helping juries understand complex technological issues and can significantly influence the outcome of a case.

For more information on this topic, please contact Fitch Even partner Steven M. Freeland or technical writer Lindsay Boehme, authors of this alert.

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Steve Freeland
Partner

Steven M. Freeland

Steven M. Freeland practices in all areas of intellectual property law, focusing primarily on the development, protection, and management of intellectual property. Steve assists clients with sophisticated patent portfolio management and the prosecution of complex patents, helping them to manage their patent assets using strategies tailored to further their business objectives.