In Aller v. Rodgers Machinery Mfg. Co., 268 N.W.2d 830 (Iowa 1978), the plaintiff sought to have his expert testify on the question of whether a product design was dangerous to the operator when used in the manner and purpose for which it was intended. Id., at 832. The district court sustained an objection to the testimony. In affirming the evidentiary ruling on appeal, the Court concluded: "The court here would have been correct in considering the question at issue as one calling for an opinion on a question of law. The law of strict liability requires that a defective product must be unreasonably dangerous to the user. The requirement of unreasonable danger is a legal standard upon which no witness, expert or non-expert, may express an opinion as to whether or not the person or the conduct or the product measures up to that standard." Id. at 840.