Also known as: but-for causation · but for test · cause in fact · actual cause · factual causation
Written by attorneys · grounded in primary & secondary sources — see below
A factual causation test requiring that the plaintiff's harm would not have occurred in the absence of the defendant's conduct. The inquiry focuses on whether the defendant's act was necessary for the result. Satisfaction of this test is a prerequisite to liability in both tort and criminal cases even when additional limits such as proximate cause also apply.
Brianna Burke and Brenda Booth both fire shotguns toward a flock of birds and one pellet strikes a bystander. The injured party cannot identify which gun caused the wound. Each defendant must show that her shot was not the but-for cause of the injury or both face liability.
Brittany Bell stabs Bella Barnes during an argument. The wound sets off a chain of infections that ultimately causes death eighteen months later. Even though the stabbing plainly satisfies but-for causation, the common-law temporal limit prevents any homicide charge.
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Brendan Burns challenges the seizure of drugs found after officers enter his home without knocking. The officers would not have discovered the evidence without the unlawful entry. The but-for link between the violation and the discovery is therefore satisfied.
Bianca Baker develops cancer after exposure to DES manufactured by several companies. She cannot prove which firm supplied the particular pills her mother took. But-for causation is presumed against all producers who cannot exonerate themselves under the market-share rule.
Boulder Construction supplies a grinding tool whose defective design causes a worker's hand injury. The worker would not have been injured if the tool had contained the missing safety feature. The defect therefore meets the but-for test for liability.
Beacon Bank fires Baxter Dynamics employee Brendan Burns. The decision would not have been made absent the manager's consideration of Burns's age. The but-for causation requirement for an ADEA claim is therefore satisfied.
But-for causation asks only whether the harm would have occurred without the defendant's conduct. Proximate cause adds a further limitation based on foreseeability and policy. Both must be satisfied before liability attaches.
Yes. The common-law rule prevents homicide liability once the one-year-and-a-day period expires regardless of whether the defendant's act was the but-for cause of death.
The burden shifts when multiple negligent defendants each could have caused a single indivisible harm and the plaintiff cannot identify which act was the actual cause. Each defendant must then prove its conduct was not the but-for cause.
Yes. The plaintiff must show that competent representation would have produced a different outcome. Failure to establish this factual causation defeats the claim even if negligence is proven.
…will be advanced. The purpose of terminal sedation is to ease the suffering of the patient and comply with her wishes, and the actual cause of death is the administration of heavy doses of lethal sedatives. This same intent and causation may exist when a doctor complies with a patient's request for lethal medication to hasten…