In the battle over class certification, expert testimony proffered by both plaintiffs and defendants is playing an increasingly important role. The Supreme Court has not yet decided whether the test for admissibility of expert testimony announced in Daubert v. Merrell Dow Pharmaceuticals applies at the class-certification stage, although it has certainly dropped hints to that effect, including in Wal-Mart Stores, Inc. v. Dukes. In our view, it’s only a matter of time before the Supreme Court expressly holds that Daubert applies to expert testimony offered in support of or opposition to class certification.

Accordingly, defendants should pay careful attention to Daubert’s standards—both in bolstering their own experts and in attacking the experts put forward by plaintiffs. The wisdom of doing so was recently underscored by the Ninth Circuit’s sharply-divided en banc decision in Estate of Barabin v. AstenJohnson, Inc. (pdf). As my colleagues Evan Tager and C.J. Summers explain in a recent alert, Barabin “significantly strengthened and expanded the gatekeeper role of both trial and appellate courts in determining whether to admit expert testimony.” Their discussion of Barabin is well worth reading for all class-action practitioners.