Class certification is often the most significant stage of a putative class action. If granted, a plaintiff’s individual claims can be transformed into claims asserted on behalf of hundreds or thousands, subjecting a defendant to substantial additional exposure. On the other hand, if class certification is denied, it can be the death knell of the litigation, as the reduced stakes no longer justify investment by the named plaintiffs or their counsel.
Because of the significance of class certification, parties often invest in expert evidence to support, or oppose, a class-certification bid. For example, expert evidence is frequently offered in the context of antitrust class actions, to determine whether “anti-trust impact” can be established using common proof; in product liability class actions, to determine whether a common design defect exists that predominates over individual issues; and in employment class actions, to determine whether there is a common pattern or practice of discrimination that affects the class as a whole. As the trend of offering—and challenging—expert evidence at the class-certification stage has become more common, the following question has come to a head: Does Daubert apply at the class-certification stage and, if so, to what extent does it apply?