To prove your personal injury claim, you (the plaintiff) must show that the defendant owed plaintiff a duty, that defendant breached that duty, that defendant’s actions caused his injury and that the injury resulted in damages.  With motor vehicle accidents, the cause leg of the personal injury table is sometimes the weakest. Arizona jury instructions on causation state that a negligent act “causes” an injury if it helps produce the injury and if the injury would not have happened without the negligence.  However, what happens when the Plaintiff’s injury is caused by two or more acts of negligence?

In a 1998 case, the Supreme Court of Arizona considered this issue.  Plaintiff Henry Piner was rear-ended and injured in separate motor vehicle accidents that occurred within hours of each other.  Mr. Piner filed lawsuits against both of the motorists that had rear-ended him.  However, attorneys for the two defendant motorists filed motions demanding that Mr. Piner had the burden of proving just which one of them was responsible for what percentage of his damages.  The Court agreed and Mr. Piner appealed.

On appeal, the Supreme Court reversed the lower ruling finding that the Indivisible Injury Rule applied.  The Court acknowledged that, “black letter tort law” tells us that an essential element of a personal injury action is that plaintiff must provide evidence that the defendants conduct caused plaintiffs damages.  A plaintiff’s case must fail if that plaintiff is unable to establish that his injury is attributable to a defendant’s conduct.

The Court found, however, that there is an exception to this general rule.  Where the negligence on the part of two defendants is clear, as in Mr. Piner’s case and it is only the issue of causation that is in doubt, the burden of proving causation shifts to the defendants.  This rule only applies when successive acts of negligence by two or more defendant’s results in, “two injuries yielding in indivisible result.”  The Court concluded that in an indivisible injury case, the fact finder is to compute the total amount of damages sustained by the plaintiff and the percentage of fault of each tortfeaser.  Multiplying the first figure by the second gives the maximum recoverable against each tortfeaser.


This blog should be used for informational purposes only. It does not create an attorney-client relationship with any reader and should not be construed as legal advice. If you need legal advice, please feel free to contact Personal Injury Attorney, R. Scott Currey at  480.461.5363, log on to,  or contact an attorney in your area.