As an essential element of the action, the plaintiff must provide evidence that the defendant's conduct caused plaintiff's damage. The law recognizes an exception for multiple, culpable actors if the plaintiff, through no fault of his own, was unable to apportion causation for a single injury. In such instances, many courts placed the burden of proof on the issue of causation apportionment upon the defendants.
While driving, the injured man was struck in two separate incidents by the drivers on the same day. There was no medically feasible way to prove how much of his injuries resulted from which collision. The injured man moved for partial summary judgment on the issue of joint and several liability against the drivers. The trial court denied the motion, holding that the Uniform Contribution Among Tortfeasors Act (UCATA), Ariz. Rev. Stat. §§ 12-2501 to 12-2509, abolished joint and several liability and that the injured man did not meet either of the two exceptions. The injured man appealed. The court reversed, holding that UCATA did not require limiting the drivers' liability by apportioning damages. Rather, UCATA apportioned fault. The court held that if the injured man established that the conduct of the drivers contributed to his injures, the burden of apportionment was on the drivers.
Did the trial court err when it ruled that on the issue of joint and several liability the injured plaintiff had to prove apportionment of damages resulting from two separate collisions before he could recover?
If a plaintiff proves that the conduct of multiple defendants contributed to damages, the burden of proof on apportionment is on them. If the judge concludes there is no evidence that would permit apportionment, then the case should be treated as one involving indivisible injuries. If the judge further concludes there is no evidence on which to base a jury finding of inability to apportion, then the jurors must be instructed to apportion. If the evidence on the question of apportionment is conflicting, the jurors should be instructed that if they are able to apportion damages, they should do so, allocating fault and damages for each accident separately. They should also be instructed that if they are unable to apportion damages, then they are to determine the plaintiff's total damages resulting from all injurious incidents. In such case, the indivisible injury rule will apply.