Douglas Harper's Etymology Dictionary
Latin, "the thing speaks for itself."
phr. 1 The import of a thing or situation is obvious. 2 (context legal English) A maxim where the very improbable facts of an accident imply the negligence of the defendant. It effectively shifts the burden of proof to the defendant.
n. a rule of evidence whereby the negligence of an alleged wrongdoer can be inferred from the fact that the accident happened
In the common law of torts, res ipsa loquitur (Latin for "the thing speaks for itself") is a doctrine that infers negligence from the very nature of an accident or injury in the absence of direct evidence on how any defendant behaved. Although modern formulations differ by jurisdiction, common law originally stated that the accident must satisfy the necessary elements of negligence: duty, breach of duty, causation, and injury. In res ipsa loquitur, the elements of duty of care, breach and causation are inferred from an injury that does not ordinarily occur without negligence.
Usage examples of "res ipsa loquitur".
Magna est vis consuetudinis, falsus in uno, falsus in omnibus, eadem sed aliter, res ipsa loquitur.