Also known as: but for causation rule · but-for causation · but for causation · but-for test · but for test · sine qua non causation · factual causation · cause in fact
Written by attorneys · grounded in primary & secondary sources — see below
A test for factual causation that asks whether the harm would not have occurred when and as it did in the absence of the defendant's act or omission. The inquiry focuses on whether the conduct was a necessary condition for the result.
Benito Benitez and Bharat Bhatia each negligently fired shots toward a crowd during a confrontation, and one bullet struck Brianna Burke. Because the evidence cannot identify which shot caused the wound, the court shifts the burden to each defendant to prove his conduct was not the but-for cause of the injury. If neither can do so, both face liability for the single harm.
Bella Barnes stabbed Bradley Banks during an argument. Banks lingered for nineteen months before dying from complications of the wound. Even though the medical evidence shows the stabbing was a but-for cause of death, the prosecution cannot charge homicide because the death fell outside the common-law temporal limit.
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Blue Horizon Industries sold a power tool to a buyer who later removed its safety guard. The buyer was injured when the altered tool kicked back. The court examines whether the original design would have prevented the injury but for the buyer's post-sale modification, concluding the change severed the but-for link to the manufacturer's conduct.
Brittany Bell developed cancer after her mother took DES during pregnancy. Multiple manufacturers produced the identical drug, and Bell cannot prove which company supplied the pills her mother ingested. The court applies market-share liability so each producer is responsible for the portion of harm corresponding to its share of the market, relaxing strict but-for proof.
Beacon Bank fired Bella Barnes after she filed an internal complaint about discrimination. Barnes proves the complaint was a but-for cause of the termination because the bank would not have acted absent her protected activity. The court requires this showing to establish liability under the governing statute.
Brookside Pharmaceuticals sold a home to Brianna Burke without revealing its prior use as a murder site. After purchase, Burke discovered the history and the market value fell sharply. The court determines whether the nondisclosure was a but-for cause of the diminished value by asking whether the price would have been the same had full disclosure occurred.
But-for causation is the factual test asking whether the harm would not have occurred absent the conduct. Proximate causation adds a legal limit that the harm must also be a foreseeable and sufficiently direct result of that conduct.
Yes. When a defendant has a legal duty to act, such as a nurse required to monitor a patient, the omission satisfies but-for causation if the harm would not have occurred when and as it did had the duty been performed.
Even when the defendant's conduct clearly meets the but-for test, the common-law year-and-a-day rule bars homicide liability if death occurs after the period expires. The temporal limit operates independently of factual causation.
…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…