Alternative liability is a legal doctrine that allows a plaintiff to shift the burden of proving causation of her injury to multiple defendants, even though only one of them could have been responsible.
The typical case showing the principle of alternative liability in action is Summers v. Tice, where the two defendants negligently shot in the direction of the plaintiff and two pellets caused the plaintiff's injury, one in the right eye and one in the upper lip.
The underpinning of this doctrine is that a plaintiff should not be barred from seeking recovery simply because she does not know who caused her injury.
Distinguish alternative liability from the smoke-out function of res ipsa loquitur seen in the leading case of Ybarra v. Spangard.
Thus, in the smoke-out function of res ipsa, the burden is shifted on the defendants to show negligence, whereas in alternative liability all defendants are all shown to have breached a duty of reasonable care and the plaintiff shifts the burden to show causation.