The Federal Circuit Continues to Evolve Its Daubert Gatekeeping Framework: Willis and Exafer

Why It Matters

These rulings tighten the standards for admissibility of patent‑damages expert testimony, compelling experts to craft comprehensive, methodologically sound reports and to substantiate any non‑standard royalty bases with a proven causal link, thereby shaping litigation strategy and potentially influencing damage awards in patent cases.

Summary

The Federal Circuit’s recent en banc decisions in Willis Elec. Co. v. Polygroup Ltd. and Exafer Ltd. v. Microsoft Corp. refine the Daubert gatekeeping framework established in EcoFactor. Willis holds that a district court must evaluate an expert’s reliability using the entire expert report, not merely the testimony presented at trial, and that methodological flaws in the report cannot be cured by trial explanation alone. Exafer overturns a lower‑court rule barring royalty bases tied to unaccused products, stating such bases are permissible if the expert demonstrates a causal connection between the patented features and the value of the unaccused product, grounded in the evidentiary record. Together, the cases give litigants clear guidance on the evidentiary scope for Daubert challenges and the technical foundation required for royalty‑base calculations.