Piner v. Superior Court
Arizona Supreme Court
962 P.2d 909 (1998)
William Piner (plaintiff) was rear-ended twice in one day by two different drivers, Billy Jones and Cynthia Richardson (defendants), each time while stopped to let pedestrians cross, and reported similar neck, back, arm, and head pain to his physician after both collisions; his treating physician could not attribute any specific portion of his injuries to either individual accident. Piner sued both drivers for his indivisible combined injuries, and while both sides agreed both collisions contributed to his total harm, neither defendant could apportion fault between them; Piner moved for partial summary judgment arguing the defendants, not he, bore the burden of proving apportionment, and if they failed, should be held jointly and severally liable. The trial court denied the motion, the court of appeals declined review, and the Arizona Supreme Court granted certiorari.
Whether, when the tortious conduct of more than one defendant contributes to a single indivisible injury, the burden falls on each defendant to prove how fault should be apportioned among them.