Yesterday, in Comcast Corp. v. Behrend, 569 U.S. __ (2013), the Supreme Court answered a looming class certification question left open by Wal-Mart Stores, Inc. v. Dukes, 564 U.S. __ (2011): whether a putative class action plaintiff must offer credible evidence of damages applicable on a class-wide basis before the district court can certify a class under Federal Rule of Civil Procedure 23(b)(3). In a 5-4 opinion, the Court answered yes. The decision promises to have particularly significant implications in putative antitrust, employment, and consumer protection class actions, where plaintiffs traditionally rely on simplified assumptions and modeling at the class certification stage to persuade courts that proof of class-wide damages would be possible. The Behrend decision confirms that defendants in such cases should not overlook potential flaws in putative class plaintiffs’ damages theories at the outset of the case.

Background. Dukes made clear that preliminary issues of class certification will likely require district courts to resolve “overlapping” merits questions. Dukes did not, however, answer how courts should resolve overlapping merits questions, and lower courts have differed significantly in the level of scrutiny they apply to those questions and to the evidence that is submitted at the class certification stage. Behrend—the first Supreme Court decision to apply Dukes—directly addresses that issue by requiring a district court to scrutinize a class plaintiff’s damages evidence at the class certification stage to ensure that evidence could actually prove damages on a class-wide basis for the particular liability theory asserted.