Class action plaintiffs often submit expert testimony in support of class certification motions, raising the question of how defendants should respond—particularly when the plaintiff’s evidence is unreliable or otherwise deficient.

(Reprinted with permission from the February 13, 2018 edition of the “The Recorder” © 2017 ALM Media Properties, LLC. All rights reserved. Further duplication without permission is prohibited, contact 877-257-3382 or

Federal courts have long applied, to varying degrees, the admissibility standards set forth in Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 570 (1993), to expert evidence submitted in connection with class certification proceedings. Daubert requires the trial court to scrutinize the reliability and relevance of expert testimony, ensuring that the evidence meets basic thresholds before it is admitted.

The California Supreme Court articulated a similar admissibility standard in Sargon Enterprises v. University of Southern California, 55 Cal. 4th 747 (2012). Sargon, which involved expert opinions presented at trial, directs the trial court to act as a gatekeeper and ensure that an expert’s opinions are not speculative and are based on, and reasonably supported by, proper data.