Also known as: sole causes · sole causation · sole proximate cause
Written by attorneys · grounded in primary & secondary sources — see below
A factor that alone produces a particular result or effect without contribution from any other factor. The determination turns on whether the conduct or event in question would have brought about the outcome even if all other forces had been absent.
Spencer Silver, threatened with a knife, strikes his attacker once with a bat. The blow fractures the attacker's skull. At trial the jury finds that Silver's single strike was the sole cause of the serious injury because no other force contributed to the fracture.
Seth Shapiro and a companion each fire once at a quail. One pellet strikes Selena Singh in the eye. Because either shot could have been the sole cause of the injury, the court shifts the burden to the defendants to prove which one was not responsible.
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Sophia Singh misses work solely because of a normal pregnancy. The state disability program denies benefits on the ground that the pregnancy itself was the sole cause of her inability to work, excluding coverage for that condition.
Solomon Silver's company shows that many qualified applicants simply prefer other jobs. The court accepts that innocent applicant preferences, not discrimination, were the sole cause of the racial imbalance in its workforce.
Simon Stern's physician assistant injects Phenergan into an artery despite a legible warning. The court finds that the assistant's independent decision was the sole cause of the resulting injury, breaking any causal link to the drug label.
Southland Foods' employee drops a package that explodes and injures a distant bystander. The court holds that the bystander's presence was so remote that the employee's act was not the sole cause of the harm under the zone-of-danger test.
A plaintiff's conduct is the sole cause when the evidence shows that the harm would not have occurred without the plaintiff's negligent choice and that no other party's conduct contributed. Courts remove the issue from the jury only when reasonable minds could reach only one conclusion on that point.
No. An intervening force such as wind is not the sole cause if the defendant's prior negligence created the precise vulnerability that the force exploited. The defendant's conduct remains a legal cause when the force was among the risks that made the conduct unreasonable.
No. When a supplier fails to warn of a known nonobvious danger, predictable user errors remain within the risk created by the omission and therefore do not become the sole cause that cuts off liability.
If one party's conduct is found to be the sole cause, comparative-fault apportionment is unnecessary because no other conduct contributed to the harm. The finding therefore bars recovery or shifts full responsibility without percentage allocation.
…it about.” (Rest., Torts, § 432.) Dean Wigmore has this to say: “When two or more persons by their acts are possibly the sole cause of a harm, or when two or more acts of the same person are possibly the sole cause, and the plaintiff has introduced evidence that the one of the two persons, or the one of the same…