by Dennis Crouch
The Federal Circuit has a new expert witness case -- this time siding with the patentee and finding that two experts were improperly excluded mid-trial. But, the case includes a sharp dissent over where to draw the line between a court's Daubert gatekeeping function and the jury's role as factfinder. Barry v. DePuy Synthes Companies, No. 2023-2226 (Fed. Cir. Jan. 20, 2026).
In the case, the experts had presented testimony that strayed somewhat from the court's claim construction and also included survey results using questionable methodology. Writing for the majority, Judge Stark concluded that this testimony was (1) permissible applications of the court's claim construction and (2) that methodological criticisms went to evidentiary weight rather than admissibility. Judge Prost dissented, warning that the majority's approach "contravenes the principles embraced in EcoFactor and the 2023 amendments" to Federal Rule of Evidence 702 and "will undermine district courts' abilities to exercise their important gatekeeping function."
The dispute in this case highlights a conceptual tension in how we think about expert testimony standards. All testimony must clear a basic relevance threshold to be admissible. At the other end of the spectrum, we have a higher standard for actually carrying the burden of proof and sustaining a verdict. Expert testimony occupies middle ground. Rule 702 and Daubert impose reliability requirements that exceed ordinary admissibility standards, recognizing that experts wield particular influence over juries. But, where exactly expert testimony sits on this spectrum (and who decides) is the central tension between the majority and dissent.