Summers v. Tice 两人开枪不知谁的子弹致害，怎么办？ Shift Burden of Proof

In Summers v. Tice, two hunters simultaneously fired their guns and one pellet of shot struck a third member of the party. Instead of dismissing the action against both for lack of conclusive proof against either, the court shifted the burden of proving lack of causation to the two defendants." Thus, the innocent plaintiff was allowed to recover where the negligence of the defendants was clear and only the issue of causation was in doubt.

The holding in Summers was predicated in part upon the celebrated decision in Ybarra v. Spangard. While that case dealt primarily with a res ipsa laquitur situation, the practical difficulties were similar. There the plaintiff sustained an injury while anesthetized on an operating table. The burden of demonstrating which among the many doctors and nurses who had participated in the operation had caused the injury proved to be impossible. In view of the unfairness of this burden, the court came to the plaintiff's aid and held that under the res ipsa loquitur doctrine, plaintiff could maintain his claim against everyone who had any connection with the operation, and the burden was on the individuals to show their non-involvement.