Sixth Circuit Applies FRE 702 to Class Certification Experts and Highlights Commonality and Predominance Issues for Products That Change Over Time

Class certification decisions under Rule 23 of the Federal Rules of Civil Procedure mark a critical stage in any putative class action lawsuit. Rule 23(a) requires plaintiffs to prove, among other things, that “there are questions of law or fact common to the class.” And Rule 23(b) authorizes money damages class actions only where the legal or factual questions common to the class predominate over questions that may be addressed differently for individual class members. In class actions involving claims about product performance, class proponents almost always cite the existence of a “defect” as common issue. But why is the generic question of “defect” even the right question, and what if the product has experienced a significant change over the time period covered by the class action? When a product is updated, is it still the same “product” for purposes of Rule 23? The Sixth Circuit, in In re: Nissan North America, Inc., --- F.4th ---, 2024 WL 4864339 (6th Cir. 2024), addressed not only these questions but also joined the growing list of circuits that expressly require expert testimony offered at the class certification stage to satisfy Rule 702 of the Federal Rules of Evidence.