The U.S. Court of Appeals for the Federal Circuit in NexStep, Inc. v. Comcast Cable Commc’ns, LLC issued a precedential decision affirming a district court’s order vacating a jury verdict of infringement because it was supported by nothing more than “word salad” from the patent holder’s expert witness. The court found the expert testimony deficient in several respects, but mainly found it lacking for failing to explain “what the function, way, and result of both the claimed device and the accused device are, and why those functions, ways, and results are substantially the same.”

This failure left the patentee unable “to prove – with particularized testimony and linking argument – that the elements of the [accused] arrangement were substantially the same as the elements of the claimed arrangement.”

Patent infringement under the doctrine of equivalents is a limited exception to the requirement that each element of the claim as literally written is present in the accused device or process. Infringement by equivalents can be shown in two ways: 1) the “function-way-result” test, i.e., the accused product or system performs substantially the same function in substantially the same way to obtain the same result or 2) that any differences between the claimed invention and the accused device or system are insubstantial.

In either situation, however, finding infringement by equivalents is “exceptional.” Here, the Federal Circuit provides a reminder of both the “special vigilance” courts must employ to avoid overbroad applications of the doctrine of equivalents and the “specific evidentiary” demands required to prove infringement under this theory.

Expert Testimony Focus

In the case at hand, which involved a method of initiating a device troubleshooting session through “a single action performed by a user,” the expert made general reference to user actions, but never identified what particular element in the accused computer applications was equivalent to the claim limitation at issue. The supporting expert testimony also lacked a meaningful explanation of why the element was supposedly equivalent. Moreover, while the parties did not disagree on the function of the claim limitation at issue, the patentee’s expert did not explicitly say what that function was.

Instead, the expert simply concluded that the accused applications perform the same function as claimed in what the Federal Circuit characterized as “because I said so” fashion. The expert never explained why the function was the same.

In addition, the expert did not identify in his testimony in what way the accused applications or claimed process operate or why they allegedly operate in substantially the same way – instead, the district court said the related testimony was “word salad.” The Federal Circuit also agreed that the expert’s generalized testimony was insufficient to support why the results of the claimed single user action are substantially the same as those of the accused applications.

Because infringement under the doctrine of equivalents requires insight from the perspective of a person skilled in the art – typically from expert witness testimony – the appeals court affirmed the district court’s opinion that there was insufficient evidence to support the jury’s infringement verdict.

The Federal Circuit also dispatched the patent holder’s remaining arguments under the “insubstantial differences” test because the expert testimony failed to provide particularized testimony and linking argument as to the “insubstantiality of the differences” between the claimed invention and the accused application that was required to show infringement under the doctrine of equivalents.

Takeaways

This decision provides a good reminder to litigants of the demands of establishing infringement under the doctrine of equivalents. These demands exist regardless of the simplicity of the technology and should not be overlooked by patentees, especially when preparing expert infringement reports and creating a record at trial. Infringement by equivalents should not be treated as an afterthought and will not be sustained based on an expert’s unproven statements or mere recitation of the “function-way-result” or “insubstantial differences” tests.