Rigorous Analysis of the Class Certification Expert: The Roles of Daubert and the Defendant's Proof

Article excerpt


A lawsuit may not be certified as a class action unless the named plaintiff shows that the central facts of the case will be proved on a class-wide basis.1 The named plaintiff often attempts to meet this burden through an expert witness, who opines that the case's material facts, which would seem to require individualized inquiries from each class member, can instead be proved through a common formula on behalf of the entire class. The defendant invariably responds with his own expert, who opines that the plaintiffs expert has oversimplified the matter and that the facts at issue cannot be proved without individualized inquiries from the class members. Two important questions arise regarding the district court's use of expert opinion testimony at the class certification stage. First, how closely should the district court scrutinize an expert's opinion? In Daubert v. Merrell Dow Pharmaceuticals, Inc., the Supreme Court emphasized that courts must look beneath the surface of expert opinions, closely examine the expert's methodologies, and exclude testimony that is irrelevant or unreliable.2 But the Supreme Court has never addressed whether the district court must subject expert testimony to Daubert's strictures at the certification stage.

Second, assuming both parties' experts pass muster under Daubert, should the district court resolve fact disputes between the opposing experts where class certification would be appropriate under one set of facts but not another? At first blush, the Supreme Court's statements regarding how deeply the district court should delve into the factual underpinnings of the parties' claims and defenses seem to conflict. In an early case, Eisen v. Carlisle & Jacquelin, the Court stated that the district court may not conduct a "preliminary inquiry into the merits" in deciding whether to certify the class.3 A few years later, the Court reversed course, requiring district courts to undertake a "rigorous analysis" of the facts offered at the class certification stage, "probfing] behind the pleadings" to discern whether the case could be effectively adjudicated as a class.4 These rather vague standards do not specifically address how the district court should assess competing expert testimony at the class certification stage, and the Court has never focused on me issue.

In the absence of clear guidance, the federal circuit courts have adopted three different approaches to class certification where the parties present expert evidence. The first approach leans heavily on Eisen's objection to "merits" inquiries.5 Courts that follow this approach refuse to subject a plaintiffs expert to a full Daubert inquiry at the class certification stage, instead conducting only a "limited" review to ensure that the expert's opinions are not "inadmissible as a matter of law."6 These courts certify the proposed class so long as the plaintiffs evidence survives this low level of scrutiny, and will not assess counterproof offered by the defendant in opposition to class certification. The second approach requires a Daubert analysis when the plaintiff offers expert testimony in support of class certification, but refuses to assess competing evidence offered by the defendant.7 This approach leaves class certification virtually automatic so long as the plaintiffs expert passes Daubert' s requirements. Finally, the third approach recognizes that Daubert and Rule 23 have wholly different requirements and serve wholly different purposes.8 The Daubert analysis merely determines whether expert testimony is sufficiently relevant and reliable to be admitted into evidence. Rule 23's requirements, on the other hand, ensure that class treatment is fair to the defendant and the absent class members alike. This approach permits an examination of the full range of evidence presented in support of and opposition to class certification. The district court makes whatever factual and legal inquiries are necessary to determine whether common issues will predominate and whether class treatment is superior to other available methods for resolving the dispute. …


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