Campbell V. General Motors Corp‪.‬

What quantum of evidence must the plaintiff in a products liability action produce initially in order to establish a prima facie case of liability under Barker v. Lull Engineering Co. (1978) 20 Cal. 3d 413 [143 Cal. Rptr. 225, 573 P.2d 443, 96 A.L.R.3d 1]?