Also known as: but-for rule · but for test · but-for test · but-for causation · cause in fact
Written by attorneys · grounded in primary & secondary sources — see below
A test for factual causation under which conduct qualifies as a cause in fact of a result if the result would not have occurred in the absence of that conduct.
Bharat Bhatia and Boubacar Bah both fire shotguns toward a shared target area without coordinating their shots. A pellet strikes Brendan Burns in the leg. Burns cannot identify which shooter caused the wound. Each defendant must show his shot did not produce the injury or face joint liability for the harm.
Brian Bailey stabs Barbara Bennett during an argument. Bennett receives treatment but dies from complications eighteen months later. The prosecution cannot establish homicide liability because the death falls outside the one-year-and-a-day window even though the stabbing supplied but-for causation.
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Bethany Boyd complains about discrimination and is later fired by Bright Path Foods. She sues under Title VII alleging the complaint prompted the discharge. The court requires her to prove the complaint was the but-for reason for the termination rather than a contributing factor.
Officers enter Blackwood Technologies headquarters without knocking and announcing their presence. They seize documents during the search. The company moves to suppress the evidence arguing the unlawful manner of entry supplied but-for causation for the discovery.
Brendan Burns uses a grinder manufactured by Benson Motors for several years and develops hand-arm vibration syndrome. He sues alleging the tool's design caused the condition. The court examines whether the injury would have occurred but for the absence of vibration-dampening features.
Barbara Bennett buys a home from Beacon Bank without learning that a notorious murder occurred inside years earlier. After discovering the fact she sues for fraud. The court assesses whether the nondisclosure was the but-for cause of her decision to purchase at the contract price.
The plaintiff must show that the harm would not have occurred in the absence of the defendant's conduct. This factual causation element is distinct from proximate cause and is ordinarily decided by the jury when evidence creates a genuine dispute.
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No. Even when but-for causation is clear the year-and-a-day rule may bar homicide charges if death occurs after the prescribed period. The temporal limit operates independently of the factual causation inquiry.
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The burden shifts in cases of unascertainable causes where multiple negligent defendants each could have caused a single indivisible harm and the plaintiff cannot identify which one actually did so. Each defendant must then prove its conduct was not the cause in fact of the injury.
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The but-for test asks whether the harm would have happened without the act. The substantial-factor test applies when multiple sufficient causes combine and focuses on whether the act played a material role in producing the result.
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…what he or she did as well.” In taking issue with this instruction, the defendants argue that the phrase “because of” requires but-for causation—a showing that they would not have acted but for the victim’s actual or perceived religious beliefs. The defendants have the better of the argument. In everyday usage, the phrase “because…