Also known as: factual causes · factually caused · factual causation · cause in fact · but-for cause · but for causation
Written by attorneys · grounded in primary & secondary sources — see below
A causal connection between tortious conduct and harm that exists when the harm would not have occurred absent the conduct. The connection is established under the but-for test and remains an element of liability even when multiple acts contribute to the outcome or when proof of which act produced the harm is impossible.
Forrest Falconer and Finn Fletcher both fired shotguns toward Farah Fox during a hunting trip. One pellet struck Fox and caused permanent injury, but ballistics could not identify which gun fired the pellet. Because both men were negligent and only one caused the harm, the court shifted the burden to each defendant to prove his shot was not the factual cause of the injury.
Francisco Frost carried a short-barreled shotgun across state lines. The government charged him with violating the National Firearms Act. The court examined whether Frost's possession of the weapon was a factual cause of the prohibited interstate movement that the statute targeted.
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A police officer stopped Farid Farahani without reasonable suspicion. During the stop the officer discovered an outstanding warrant and found drugs. The court analyzed whether the illegal stop was a factual cause of the evidence discovery or whether the warrant broke the causal chain.
Two robbers entered a store and threatened the owner, Forrest Falconer. The owner, who had severe heart disease, suffered a fatal heart attack minutes later. The prosecution had to prove that the robbery was a factual cause of the death even though the victim's preexisting condition contributed to the outcome.
Workers at Foster Forge used pneumatic tools that transmitted excessive vibration. Francesca Fiore developed permanent nerve damage in her hands. The court required her to show that the tool design was a factual cause of her injury rather than other workplace factors.
Francesca Fiore's mother took DES manufactured by several companies during pregnancy. Fiore later developed cancer linked to the drug. Because she could not identify which manufacturer supplied the particular pills her mother ingested, the court applied market-share liability after confirming each defendant's product was a factual cause of the type of harm.
Courts apply the but-for test: conduct is a factual cause if the harm would not have occurred absent the conduct. The Restatement (Third) of Torts §26 codifies this standard and treats factual cause as a necessary condition for liability.
Supporting sources
Under Restatement (Third) of Torts §27, each act is treated as a factual cause even if either one alone would have produced the identical harm. This rule prevents defendants from escaping liability simply because another sufficient cause was also present.
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When two or more defendants acted negligently toward the plaintiff and only one caused the single harm, but the plaintiff cannot identify which one, the burden shifts to each defendant to prove his conduct was not a factual cause. If a defendant cannot meet that burden, he remains liable.
Supporting sources
…112, at 6–8 (Iowa Ct. App. 2009) (table decision) (holding that the State must show that the discriminatory motive was the cause in fact of the offense to establish a hate crime under Iowa law), aff’d in relevant part, 791 N.W.2d 828 (Iowa 2010). The government separately points to a case involving Section 1 of the Hate…