Res ipsa loquitur is a doctrine of circumstantial evidence in tort law that permits a court or jury to infer a defendant's negligence without direct proof, when the nature of the accident itself suggests that someone in the defendant's position must have been at fault. The phrase is Latin and translates literally as "the thing speaks for itself."
The doctrine is generally traced to the English case Byrne v. Boadle (1863), in which a barrel of flour fell from a warehouse window and struck a passerby. Chief Baron Pollock reasoned that such an event does not ordinarily happen without negligence, and the plaintiff could not be expected to prove exactly how the barrel came loose. Later, Scott v. London and St Katherine Docks Co. (1865) formulated the classical three-part test still cited today:
- the accident is of a kind that ordinarily does not occur in the absence of negligence;
- the instrumentality causing the harm was under the exclusive control of the defendant; and
- the injury was not due to any voluntary action or contribution by the plaintiff.
In the United States, the doctrine was famously applied in Ybarra v. Spangard, 25 Cal.2d 486 (1944), where a patient injured during surgery while unconscious was allowed to invoke res ipsa against multiple medical staff. It is also codified in part in the Restatement (Second) of Torts § 328D and the Restatement (Third) of Torts: Liability for Physical and Emotional Harm § 17.
Although primarily a domestic tort concept, the underlying logic — drawing inferences from circumstances when direct evidence is unavailable — appears in international law contexts, including the International Court of Justice's reasoning in the Corfu Channel case (UK v. Albania, 1949) on indirect evidence of state responsibility. Civil-law jurisdictions reach similar outcomes through doctrines such as the French faute présumée or the German Anscheinsbeweis (prima facie evidence).
Res ipsa typically shifts the burden of production, not the ultimate burden of persuasion, though jurisdictions vary.
Example
In *Byrne v. Boadle* (1863), when a flour barrel fell from a warehouse window onto a pedestrian below, the English court inferred negligence on the part of the warehouse owner under res ipsa loquitur because such accidents do not ordinarily happen without carelessness.
Frequently asked questions
In most common-law jurisdictions it shifts only the burden of production, requiring the defendant to offer an explanation, while the ultimate burden of persuasion remains with the plaintiff. Some jurisdictions treat it as creating a rebuttable presumption.
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