Class certification is the feature fight of any putative class action lawsuit. If granted, it can multiply the stakes of a case several hundred- or thousand-fold. If denied, it can signal the end of the litigation. Because of its importance, parties often invest heavily in the class certification fight, including by offering – and challenging – expert testimony.
As this trend has become more common, more focus has been devoted to answering a key question – to what extent should Rule 702 apply at this critical juncture? A number of circuits have held that Rule 702 applies in full force and that opinions deemed inadmissible under Rule 702 should not be considered in regard to class certification; others, such as the Ninth Circuit, have taken a somewhat different approach. Recently, the Southern District of California, in Stewart v. Quest Diagnostics Clinical Labs., Inc., 2022 WL 5236821 (S.D. Cal. Oct. 5, 2022), weighed in on this question.