Joshua D. Anderson, left, and Terence N. Hawley, right, of Reed Smith. Joshua D. Anderson, left, and Terence N. Hawley, right, of Reed Smith.

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.

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.

Unfortunately, as to expert evidence presented in connection with class certification motions, California state courts have arguably been less clear than their federal counterparts regarding the applicable legal standards and proper level of scrutiny. Recent California decisions, however, suggest that the tide may be turning in the defendants’ favor and provide additional ammunition for attacking dubious expert evidence at the certification phase.

Apple Inc. v. Superior Court (Shamrell), D072287, ___ Cal. App. 5th ___ (Jan. 29, 2018)

In Shamrell, the Fourth Appellate District vacated an order certifying classes of purchasers of various iPhone models, finding that the trial court committed prejudicial error by refusing to apply Sargon’s admissibility standards to the plaintiffs’ expert witness declarations.

The plaintiffs in Shamrell alleged that Apple sold certain iPhones with power buttons that malfunctioned or failed during the warranty periods, in violation of various California consumer protection statutes and warranty laws. Plaintiffs sought damages and other relief, and moved for class certification. As support, plaintiffs offered declarations from experts who opined that damages could be established on a classwide basis. Two experts sought to establish damages with documents reflecting the amounts Apple charged customers to repair the iPhone buttons or showing the diminution in trade-in values for the affected phones. Another expert opined that he could determine damages through a “conjoint analysis” that purported to show the value consumers placed on various features, including the power button.

Apple responded that these expert opinions were unreliable under Sargon because, among other problems, they focused mainly on the risk of a defect at the time of sale without reference to class members’ actual post-sale experiences (e.g., receipt of the full trade-in value). The trial court nevertheless certified plaintiffs’ proposed classes, concluding that Sargon did not apply and that the reliability of plaintiffs’ experts was a class-wide issue for trial.

The court of appeal vacated the order, holding that the trial court erred by declining to apply Sargon. The court saw “no reason why Sargon should not apply equally in the context of class certification motions,” stating that “there is only one standard for admissibility of expert opinion evidence in California, and Sargon describes that standard.” The court also found the trial court’s ruling prejudicial: had Sargon been applied, the declarations may have been excluded due to issues with the experts’ opinions that were never sufficiently explained or addressed.

Duran vs. U.S. Bank National Association, A148817, ___ Cal. App. 5th ___ (Jan. 17, 2018)

In the latest installment in a long-running wage-and-hour case, the First Appellate District affirmed a trial court order denying class certification on the grounds that the plaintiffs’ survey data was unreliable and failed to establish their case was manageable as a class action. Notably, the trial court did not reference Sargon or exclude plaintiffs’ survey evidence. Instead, it considered the evidence in detail and determined it was insufficient for certification purposes.

In Duran, the named plaintiffs alleged that a bank improperly classified its business banking officers (BBOs) as overtime exempt under the outside salesperson exemption, which applies only to employees who spend more than 50 percent of their workday on sales outside their employer’s place of business. The bank filed a motion to deny class certification. In response, plaintiffs submitted the results of a 2015 survey conducted by their expert, which supposedly showed that 95.45 percent of respondents reported spending 50 percent or less of their workday performing outside sales activities. Plaintiffs later submitted a trial plan that proposed to use testimony from different samples of BBOs to establish liability and restitution.

On reply, the bank submitted a declaration from its own survey expert, who opined that the 2015 survey suffered from self-selection bias and significant measurement and estimation errors. The trial court denied class certification, finding the results of the 2015 survey were unreliable and failed to show uniformity in how BBOs spent their time. The trial court further determined that it could not manage the bank’s affirmative defense that at least some BBOs worked most of their time outside of the office.

The court of appeal affirmed, holding that the trial court did not abuse its discretion in ruling that the 2015 survey was unreliable. Significant differences existed between the results of the 2015 survey and a 2008 survey of the same population by the same expert. For example, the estimated number of overtime hours per week nearly doubled in the 2015 survey, with no explanation by plaintiffs. Therefore, substantial evidence supported the trial court’s finding that the 2015 survey was unreliable as evidence of uniformity on how BBOs spent their time and as a basis for selecting representative samples of witnesses to testify on liability and restitution.

ABM Industries Overtime Cases, A132387, A133077, A133695, 19 Cal. App. 5th 277 (Dec. 11, 2017; pub. ord. Jan. 10, 2018)

In ABM Industries, the First Appellate District reached a different result, but its reasoning appears to be consistent with Shamrell and Duran. The ABM plaintiffs sued a janitorial services company for violations of California labor laws and moved for certification of various classes allegedly subjected to different wage-and-hour violations. Plaintiffs included in their supporting evidence expert declarations from Aaron Woolfson, who analyzed timekeeping and payroll data the defendant maintained. The defendant filed no formal challenge to Wolfson’s declaration and did not submit a competing opinion. The trial court still ruled, however, that Woolfson’s declarations were inadmissible and denied certification, emphasizing his lack of “‘formal training or degrees that would qualify him as an expert to review the timekeeping and payroll data at issue.’”

The court of appeal reversed. It reasoned that, under the California Evidence Code, expertise need not be based on formal education or professional certification and can be established in a number of ways, including by showing that the expert has the requisite knowledge, familiarity, or experience regarding a sufficient number of transactions involving the subject matter of the opinion. Here, plaintiffs’ submissions established that Wolfson had experience with numerous complex transactions sufficient to qualify him as an expert in database management and analysis. The court further concluded that, considering all of the evidence, plaintiffs had met the requirements for class certification in the context of a wage and hour case due to predominating common issues regarding the legality of the defendant’s uniform payroll policies.

While the court ultimately admitted the expert testimony and found in favor of certification, its holding emphasizes the trial court’s cursory treatment and exclusion of the plaintiffs’ sole expert based on its application of erroneous legal assumptions to his qualifications. Unlike Shamrell and Duran, there was no genuine scrutiny by the trial court—or by the defendant—of the expert’s methodology or the bases for his opinions.


Shamrell and Duran provide defendants in California state courts with additional legal support for rigorously analyzing and challenging expert evidence offered in support of class certification, and ABM Industries demonstrates the potential perils associated with failing to do so. Accordingly, defendants should consider the following steps in responding to expert evidence submitted by plaintiffs in connection with class certification proceedings:

  • Conduct expert discovery, including document discovery and depositions;
  • Retain an opposing expert or consultant (this may be appropriate even if the plaintiff is not using an expert), and remain mindful that plaintiffs, too, may challenge your expert’s opinions;
  • Submit your own expert evidence regarding the Sargon factors and class certification elements;
  • Object to or move to strike the plaintiff’s expert(s) under Sargon;
  • Argue that the plaintiff’s expert evidence, even if admitted, is insufficient to establish a basis for certification.

The optimal strategy will depend on the circumstances, but whatever the approach, these recent cases support vigorous challenges to expert evidence presented in support of class certification.

Terence N. Hawley is a partner in the San Francisco office of Reed Smith and focuses his practice on complex business disputes and class action defense.

Joshua D. Anderson is a litigation associate in the firm’s San Francisco office and joined the firm following a clerkship for Judge Robert Pitman of the Western District of Texas.