Also known as: alternative liabilities
Written by attorneys · grounded in primary & secondary sources — see below
A tort doctrine under which the burden of proving factual causation shifts to each of multiple negligent defendants when the plaintiff establishes that one of them caused a single indivisible harm but cannot identify which one due to factual impossibility created by their conduct. Each defendant must then prove that its own conduct was not the cause in fact of the injury. If a defendant fails to carry that burden, it remains liable, often jointly and severally with the others.
Ariana Azizi stepped between two illegally parked buses at a terminal. One bus lurched forward and crushed her foot. Witnesses gave conflicting accounts and security footage was inconclusive, making it impossible to determine whether the West Dispatch or Highland Transit bus made contact. Because both companies had parked negligently and created the uncertainty, the court shifted the causation burden to each company to prove its bus did not cause the injury.
Austin Abbott worked on one side of a plywood partition while Gold Construct and Swift Concrete crews fired nail guns on the other side despite warnings. A nail penetrated the partition and struck his leg. The nail was discarded before testing and both crews used identical nails, rendering it impossible to identify which crew fired the injurious nail. The court therefore required each subcontractor to prove that its crew did not cause the injury.
Select any source to read its text and confirm it supports the definition.
The doctrine shifts the burden when two or more defendants each acted negligently toward the plaintiff, the plaintiff suffered a single indivisible harm caused by only one of them, and factual impossibility prevents the plaintiff from identifying which defendant caused the injury. Each defendant must then prove its conduct was not the cause in fact. Failure to carry that burden results in liability, often joint and several.
Supporting sources
No. The doctrine applies when the plaintiff sues the negligent defendants whose conduct created the unascertainable causation and meets the other elements of multiple negligence, single harm, and factual impossibility. Courts have applied it in cases involving two or more defendants without requiring every conceivable actor to be joined.
Supporting sources
The doctrine prevents innocent plaintiffs from going uncompensated when multiple negligent defendants have created the evidentiary uncertainty that obscures which one caused the harm. It places the risk of that uncertainty on the wrongdoers rather than the victim and deters conduct that generates ambiguous causation.
Supporting sources
…may shift to the defendants to show that they were not responsible for the harm. This principle is sometimes referred to as the "alternative liability" theory. The celebrated case of Summers v. Tice , supra , 33 Cal.2d 80, a unanimous opinion of this court, best exemplifies the rule. In Summers , the plaintiff was injured when two…