Expert Testimony in Patent Cases Now Harder to Admit

A recent en banc decision by the Federal Circuit in EcoFactor, Inc. v. Google LLC (2025) — left standing by the U.S. Supreme Court’s denial of review — has sparked widespread debate in the legal community for significantly heightening the scrutiny of expert testimony under Daubert and Federal Rule of Evidence 702, and for potentially shifting decision-making power over patent damages from juries to judges.

 A recent en banc decision of the Federal Circuit Court of Appeal, which has plenary jurisdiction over all patent appeals, coupled with the subsequent very recent denial of review of the decision by the U.S. Supreme Court, has caused a stir and debate in the legal community regarding the decisions’ impact on raising the level of scrutiny accorded to expert opinion testimony in support of proving patent damages at trial and shifting the balance of decision-making power from juries to judges.

The decision, EcoFactor, Inc. v. Google LLC (Fed. Cir. 2025) 137 F.4th 1333, cert. denied (U.S., Oct. 20, 2025, No. 25-341) concerned the interpretation and application of the three-decade-old Supreme Court case Daubert v. Merrell Dow Pharmaceuticals, Inc. , 509 U.S. 579 (1993) (Daubert), and the corresponding Federal Rule of Evidence 702, dealing with admissibility of expert opinion evidence and testimony.

As background, in 2020, plaintiff EcoFactor sued Google for infringement of its patented technology related to network computer cooling and heating mechanism. In support of its damages theory at trial, plaintiff offered opinion testimony of its expert to prove a certain reasonable royalty rate per infringed product. Prior to trial, Google moved to exclude that testimony on the basis that it was inadmissible under FRE 702 and Daubert for lacking reliability and sufficient bases for its conclusion. Google’s motion was denied.

EcoFactor expert’s opinion was based on three pieces of evidence. First, three license agreements between EcoFactor and third parties involving related patented technologies, in each of which the contracting parties had agreed to the same royalty number and a total sum; second, the expert relied on the testimony of EcoFactor’s CEO, who had signed the three license agreements on behalf of EcoFactor and who testified that based on his seven years of experience in the industry and his knowledge and understanding of the market and the reasonable royalty rates, the royalty rate provided by the expert was reasonable. Finally, the expert based his opinion on an email chain between EcoFactor and a third party discussing the royalty rate for EcoFactor’s patented technology.

Following trial, the jury found Google had infringed EcoFactor’s patent and awarded it $20 million in damages. However, the jury did not break down its total awarded damages into a specific per product royalty rate. Google appealed the trial court’s decision, but a panel of the Federal Circuit Court of Appeal affirmed the trial court’s decision. Google then petitioned the appeal court for an en-banc rehearing of the panel’s decision, which the full court granted. The en banc court went on to reverse its panel’s decision on damages and held that the trial court had abused its discretion by denying Google’s motion to exclude the testimony of plaintiff’s expert.

The full court’s decision was primarily based on its interpretation of the three contracts EcoFactor’s expert had partially relied on to arrive at his reasonable royalty opinion, which the en banc court reviewed under the de novo standard without deference to the trial court and found that they did not support the expert’s opinion on a per item reasonable royalty rate.

The en banc decision is significant in many aspects. First, as the dissent noted, any error in the expert’s interpretation of the licenses could have been deemed “harmless” because other properly admitted evidence, specifically that of EcoFactor’s CEO, as well as an email chain discussing what a reasonable royalty for the technology at issue should be, were sufficient to sustain the jury verdict. Second, the jury damages award was a sum total that did not specify a reasonable royalty amount per item, which means that it was not clear whether and how much EcoFactor’s expert opinion as to per item reasonable royalty amount had contributed to the jury’s determination of that total. In fact, the decision itself acknowledged that it “cannot be sure” how or even whether the expert’s reasonable royalty opinion had influenced the jury.

The en banc decision included a lengthy and vigorous dissent, which also criticized the full court’s procedural handling of the dispute. From the perspective of the dissent, the appeal was first announced as intending to review the district court decision under an abuse of discretion standard but then shifted the focus of its analysis on the three contracts to allow itself to decide de novo. This approach, the dissent noted, had deprived the plaintiff of an opportunity to brief the issue of the interpretation of the contracts and whether they supported their expert’s royalty opinion. The dissent noted that the issue of royalty determination was fact based and a task for the jury and not the judge. The dissent’s main concern with the decision was that it may invite judges to take power away from juries and resolve fact disputes under the guise of evaluating admissibility.

There is little doubt that the EcoFactor decision constitutes a departure from the traditional treatment of expert opinion testimony by courts where challenges to sufficiency and adequacy of an expert opinion evidence and testimony have been effectuated through vigorous cross examination of the expert and clear instructions to the jury on the applicable burden of proof. EcoFactor is likely to disturb that balance and shift the power to make such determination to judges.

Dariush Adli | President