The Supreme Court has made clear that a district court may grant class action certification only after conducting a rigorous analysis to ensure that the requirements of Rule 23 of the Federal Rules of Civil Procedure have been met. Less clear, however, is what exactly a rigorous analysis entails. As precertification scrutiny has become more robust, reliance on expert testimony has become nearly indispensable for obtain­ing class certification. This Note addresses the circuit split surrounding whether expert testimony submitted during the class certification process should be subject to the gatekeeping standard set forth in Daubert v. Merrell Dow Pharmaceuticals, Inc. This Note argues that the two main approaches, each calling for some form of exclusionary Daubert analysis, give rise to concerns relating to efficiency and fairness, thus hindering the purposes of the class action mechanism. Moreover, the two approaches subject expert testimony to admissibility standards unsuitable for a preliminary stage of litigation and rely on a critical misconstruction of the Supreme Court’s rigorous analysis requirement as a gatekeeping standard rather than a fact-finding standard. This Note proposes that courts should instead adopt the approach put forth by the Ninth Circuit and consider the Daubert factors as part of an overall assessment of the probative value, rather than the admissibility, of expert testimony.

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Over the past decade, the Supreme Court has engaged in an internal game of tug-of-war over the proper scope of a district court’s scrutiny dur­ing class certification proceedings. The contest kicked off in 2011 with Wal-Mart Stores, Inc. v. Dukes, in which the Court required inquiry into the merits of a putative class’s underlying claims to the extent necessary to determine satisfaction of Rule 23 requirements. 1 564 U.S. 338, 350–51 (2011). Two years later, the match flipped when the Court, in Amgen Inc. v. Connecticut Retirement Plans & Trust Funds, limited the proper scope of precertification scrutiny in secu­rities fraud class actions. 2 See 568 U.S. 455, 467 (2013) (holding that precertification inquiry into the “materiality” prong of a fraud on the market claim was unnecessary for an evaluation of predominance). The Court emphasized that “Rule 23 grants courts no license to engage in free-ranging merits inquiries at the certification stage. Merits questions may be considered to the extent—but only to the extent—that they are relevant to determining whether the Rule 23 prerequisites for class certification are satisfied.” Id. at 466. This apparent retreat from Wal-Mart, however, was short-lived. Just a month later, in Comcast Corp. v. Behrend, the Court doubled down on its Wal-Mart holding, requiring district courts to enter­tain arguments against the propriety of class certification even when doing so would touch on the merits of class claims. 3 569 U.S. 27, 34 (2013). Finally, in 2016, the tide shifted once more, with the Court lowering the bar for the kind of evidence that can be sufficiently probative to support class certification. 4 See Tyson Foods, Inc. v. Bouaphakeo, 136 S. Ct. 1036, 1049 (2016) (finding representative evidence sufficiently probative to demonstrate predominance in the instant case).

Thus far, the Court’s key decisions in this class certification skirmish have pertained to a district court’s fact-finding role in determining whether Rule 23 requirements have been satisfied. 5 See infra notes 181–184 and accompanying text. The battle may soon shift, however, into new territory: judicial gatekeeping of expert testimony intended to support or oppose certification. As reliance on expert opinions during class certification proceedings has increased, 6 See infra notes 63–67 and accompanying text. a circuit split has developed surrounding whether expert testimony at this stage of litigation should be subject to the standard set forth in Daubert v. Merrell Dow Pharmaceuticals, Inc., which requires judges to screen out unreliable expert testimony at trial. 7 509 U.S. 579, 589 (1993). The two most established sides of the split apply differing levels of Daubert scrutiny prior to a district court’s consideration of expert testimony for the class certification inquiry. On one side, four circuits require that expert testimony pass muster under the full Daubert scrutiny typically applied at trial. 8 See infra section I.D.1. On the other, the Eighth Circuit employs a “tailored” Daubert analysis, which limits the admissibility evaluation to the reliability of the evidence for the purpose of class certification. 9 See infra section I.D.2. Meanwhile, in what this Note proposes comprises an entirely distinct third side of the split, the Ninth Circuit recently held that inadmissibility under Daubert, while relevant for assessing the probative value of expert testi­mony for the certification inquiry, should not bar evidence from consider­ation. 10 Sali v. Corona Reg’l Med. Ctr. (Sali II), 909 F.3d 996, 1006 (9th Cir. 2018), cert. dismissed, 139 S. Ct. 1651 (2019) (mem.) (holding that while a judge should fully consider the Daubert factors, inadmissibility under Daubert should not be dispositive).
Some commentators addressing the Daubert split since the Ninth Circuit’s decision in Sali II treat the Ninth Circuit and the Eighth Circuit approaches as identical due to their common view that district courts are not limited to consideration of evidence admissible at trial. See, e.g., Cianan M. Lesley, Note, Making Rule 23 Ideal: Using a Multifactor Test to Evaluate the Admissibility of Evidence at Class Certification, 118 Mich. L. Rev. 149, 162–63 (2019). This Note argues, however, that the Ninth Circuit, by declining to apply Daubert in an exclusionary fashion, differs significantly from the Eighth Circuit. See infra section I.D.3.
While the Supreme Court has danced around the split on two occasions, the Daubert issue remains unresolved. 11 See infra notes 52–53, 58–59 and accompanying text.

Significant issues arise from each of the two predominant approaches. The full Daubert approach diminishes the efficiency of the precertification discovery process and disproportionately harms plaintiffs. 12 See infra section II.A. The tailored Daubert approach, meanwhile, is rife with procedural ambiguity, which cre­ates doubts as to its workability and efficiency. 13 See infra section II.B. Perhaps most significantly, however, each side employs a version of Daubert wherein the results of the analysis determine whether or not a judge may consider the evidence at all in their certification inquiry. This imposition of an exclusionary rule improperly subjects the class certification proceeding to admissibility standards unsuitable for a preliminary stage of litigation and unduly limits judicial discretion. Furthermore, applying an exclusionary rule here fun­damentally misconstrues the Supreme Court’s directive that district courts should conduct a rigorous analysis at the certification stage as a gatekeep­ing standard rather than as a fact-finding standard. 14 See infra section II.C.

This Note analyzes the problems arising from the use of exclusionary standards to bar expert testimony from judicial consideration during class certification proceedings. Part I provides an overview of class certification, the Daubert standard, and the circuit split. Part II considers the problems posed by the full Daubert approach and the tailored Daubert approach and further considers the impropriety of engaging in either exclusionary anal­ysis. Finally, Part III proposes that, in engaging in a rigorous analysis of expert testimony at the class certification stage, courts should adopt the recent guidance of the Ninth Circuit and consider the factors of reliability and relevance espoused by Daubert without adopting the exclusionary con­sequences linked to the standard’s application to trial evidence.