Res Ipsa Loquitur

Res ipsa loquitur, Latin for "the thing speaks for itself," is a doctrine that permits a jury to infer negligence from the circumstances of an accident even without direct evidence of what the defendant did wrong. It is a powerful tool for plaintiffs who cannot prove exactly how the defendant was negligent because the evidence is within the defendant's control or has been destroyed.

The traditional elements require the plaintiff to show three things: (1) the accident is of a kind that ordinarily does not occur in the absence of negligence; (2) the instrumentality causing the harm was in the exclusive control of the defendant; and (3) the accident was not due to any voluntary action or contribution by the plaintiff. Some jurisdictions add a fourth element requiring that the evidence of the true explanation be more readily accessible to the defendant than to the plaintiff.

The doctrine originated in the English case of Byrne v. Boadle, where a barrel of flour fell from a warehouse onto a passerby. The court reasoned that barrels do not fall from warehouses in the ordinary course without someone's negligence. In Ybarra v. Spangard, the doctrine was extended to medical malpractice cases where a patient was unconscious during surgery and could not identify which member of the surgical team was negligent.

Res ipsa loquitur does not shift the burden of proof to the defendant in most jurisdictions — rather, it creates a permissible inference of negligence that the jury may or may not draw. In some jurisdictions, however, the doctrine creates a presumption of negligence that shifts the burden of production to the defendant.

The doctrine is frequently tested on torts exams because it raises issues about the relationship between circumstantial evidence and the elements of a negligence claim. Students should recognize res ipsa fact patterns — situations where something goes wrong in a way that suggests negligence, but the plaintiff lacks direct evidence of what happened.