Also known as: but-for cause · but for cause · but for causes · actual cause · cause in fact · but-for causation
Written by attorneys · grounded in primary & secondary sources — see below
A factual cause of an event or harm. Conduct qualifies when the event or harm would not have occurred in its absence.
Two trucks owned by separate companies struck Brandon Black's car in quick succession on a mountain road. Brandon cannot identify which impact caused his spinal injury. Each company must show its truck was not the but-for cause of the injury. Because neither company can do so, both face liability for the full harm.
Beatrice Brown stabbed Bethany Boyd during an argument. Bethany lingered for nineteen months before dying from complications of the wound. Even though the stabbing was a but-for cause of death, the common-law time limit prevents any homicide charge.
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Bruce Baldwin bought a pneumatic tool from Chicago Pneumatic. A coworker later removed the safety guard. The tool injured Bruce when it jammed. Because the removal was a but-for cause of the injury, the manufacturer avoids liability under the alteration defense.
Bianca Blanco sued her medical school after being fired. She proved her supervisor knew she had filed a discrimination complaint. The school showed it would have fired her anyway for poor performance reviews. Because the complaint was not a but-for cause of the termination, her retaliation claim fails.
Brenda Booth bought a house from Reed without learning it had been the site of a notorious murder. The murder history was a but-for cause of the reduced market value she later discovered. Her rescission claim therefore proceeds on a fraud theory.
Bayside Shipping bought cigarettes from Liggett. The company had warranted the product was safe. Mr. Cipollone's estate proved the warranty was false. Because the breach was not shown to be a but-for cause of his lung cancer, damages were limited to the warranty claim alone.
No. Multiple acts can each be but-for causes if the harm would not have occurred without any one of them. The test asks only whether the result would have happened absent the defendant's conduct.
Yes. Under the traditional common-law year-and-a-day rule, death must occur within one year and one day of the injury. If the victim dies later, no homicide charge lies regardless of factual causation.
The product test asks whether the offense would not have occurred but for the defendant's mental disease or defect. When experts establish that causal link, the jury must acquit even if the defendant knew the act was wrong.
When either act alone would have produced the injury, each remains a but-for cause. Courts may still impose liability on both actors under concurrent-cause principles.
…it erroneously instructed the jury in several respects on the failure to warn claim, most significantly by failing to impose a but-for causation requirement. Liggett also contends that the district court erred in failing to grant its motion for judgment n.o.v. on the express warranty claim on the grounds that (1) the jury's finding…