What is the definition of a design defect in a product liability case?

4 Barker v. Lull Engineering Co. (1978) 20 Cal.3d 413, 432, 143 Cal.Rptr. 225, 573 P.2d 443, sets forth one definition of a design defect in a products liability case to be the failure of the product "to perform as safely as an ordinary consumer would expect when used in an intended or reasonably foreseeable manner."

5 The court explained that the order in question "does not define the sort of case or factual situation to which the consumer expectation theory will apply, nor does it limit or mandate its application. Rather, it limits the sort of evidence which is admissible in those causes of action in which the plaintiff is entitled to and does rely solely upon such theory." (Vermeulen v. Superior Court, supra, 204 Cal.App.3d at p. 1199, 251 Cal.Rptr. 805.)