Magdalene M. Smoot and Ryan M. Smoot v. Mazda Motors of America, Inc. And Tokio Marine and Fire Insurance Company, Ltd.

POSNER, Circuit Judge.

The district judge, after barring the plaintiffs’ expert from testifying, dismissed this diversity personal-injury suit (the substantive issues in which are governed by Wisconsin law) on the ground that without expert testimony the plaintiffs could not prove their case.

Before reviewing that ruling, we remark the confusion in the parties’ briefs concerning the elements of the diversity jurisdiction. The jurisdictional statement in the appellants’ brief states that the federal district court’s jurisdiction was based on diversity of citizenship “and the jurisdictional…