"Frivolous" to Argue that Erie Governs Rules on Expert Testimony, Says 7th Circuit

The Federal Rules of Evidence normally govern in diversity cases, but not always. Where a state evidentiary rule is intimately bound up with the substantive claims at issue, it has sometimes been held on Erie grounds that the state rule should govern. See, e.g., Wray v. Gregory, 61 F.3d 1414 (9th Cir. 1995). Plaintiffs' lawyers from Frye states sometimes feel tempted to argue, under those broad principles, that state law should supply the rule of decision on the admissibility of expert testimony in diversity cases. A Seventh Circuit panel has now issued an opinion calling such arguments "frivolous," noting that Daubert, Joiner, and Kumho Tire were all diversity cases. See Schrott v. Bristol-Myers Squibb Co., No. 03-3950 (7th Cir. Apr. 13, 2005) (Easterbook, Wood, & Evans, JJ.).