Res Ipsa Loquitur

Definition 

Latin for "the thing speaks for itself."  
 

Overview

In tort law, a principle that allows plaintiffs to meet their burden of proof with what is, in effect, circumstantial evidence. The plaintiff can create a rebuttable presumption of negligence by the defendant by proving that the harm would not ordinarily have occurred without negligence, that the object that caused the harm was under the defendant’s control, and that there are no other plausible explanations.  

Prima Facie Case

To prove res ipsa loquitor negligence, the plaintiff must prove 3 things:

  1. The incident was of a type that does not generally happen without negligence
  2. It was caused by an instrumentality solely in defendant’s control
  3. The plaintiff did not contribute to the cause 

Limitations on Res Ipsa Loquitur

An which injury which happens without the fault of a plaintiff (i.e. certain types of slip-and-fall accidents) would necessarily fail the prima facie test, failing the third element in particular. 

Further Reading

For more on res ipsa loquitur, see this Yale Law Review note and this St. John's Law Review note

For an example of a court applying res ipsa loquitur, see Byrne v Boadle.