Res Ipsa Loquitur
Rule
“The thing speaks for itself.” A jury may infer that the defendant was negligent based on the nature of the accident itself, without direct evidence of the specific negligent act, when the accident is of a type that ordinarily does not occur without someone’s negligence, and the defendant had control over the instrumentality causing the harm.
Elements
- The accident is of the type that would not ordinarily occur without negligence (probability of negligence).
- The instrumentality causing harm was within the defendant’s exclusive control (or the defendant has superior access to information about the cause).
- The plaintiff did not contribute to the cause (or plaintiff’s contribution is discounted).
Procedural Effect (varies by jurisdiction)
- Inference (majority rule): jury may — but is not required to — infer negligence.
- Presumption (minority, e.g., California): jury must presume negligence unless defendant rebuts it.
Expansions and Modifications
- Ybarra v. Spangard: applies to multiple defendants who jointly control the plaintiff while unconscious; each defendant bears the burden to explain or exculpate. Overcomes “conspiracy of silence.”
- Restatement 3d: removes the “exclusive control” requirement; fact-finder may infer negligence when (1) the accident is of a type ordinarily caused by negligence and (2) the defendant is a member of the class whose negligence ordinarily causes such accidents.
- Constructive control: actual physical control not required; defendant’s responsibility over the risk is sufficient.
Policy
- Addresses information asymmetry: defendant has better access to evidence of what caused the harm.
- Promotes judicial efficiency.
- Prevents defendants from escaping liability through a “monopoly on information.”
Key Cases
- Byrne v. Boadle — flour barrel falling from warehouse window; foundational case establishing the doctrine.
- Ybarra v. Spangard — res ipsa applied to surgical team collectively; shifts burden to each defendant.
- McDougald v. Perry — spare tire flying from truck; accident type does not ordinarily occur without negligence.