Res ipsa loquitur (Latin: "the thing speaks for itself") is a doctrine in the Anglo-American common law that says in a tort lawsuit a court can infer 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.

History.

The term comes from Latin and is literally translated "the thing itself speaks", but the sense is well conveyed in the more common translation, "the thing speaks for itself". The earliest known use of the phrase was by Cicero in his defense speech Pro Milone. The circumstances of the genesis of the phrase and application by Cicero in Roman legal trials has led to questions whether it reflects on the quality of res ipsa loquitur as a legal doctrine subsequent to 52 BC, some 1915 years before the English case Byrne v Boadle and the question whether Charles Edward Pollock might have taken direct inspiration from Cicero's application of the maxim in writing his judgment in that case.

Elements.

1.   The injury is of the kind that does not ordinarily occur without negligence or is uncommon in the course and nature of said act.

2.   The injury is caused by an agency or instrumentality within the exclusive control of the defendant.

3.   The injury-causing accident is not by any voluntary action or contribution on the part of the plaintiff.

4.   The defendant's non-negligent explanation does not completely explain the plaintiff's injury.

The first element may be satisfied in one of three ways:

a.   The injury itself is sufficient to prove blatant or palpable negligence as a matter of law, such as amputation of the wrong limb or leaving instruments inside the body after surgery.

b.   The general experience and observation of mankind is sufficient to support the conclusion that the injury would not have resulted without negligence, such as a hysterectomy (removal of the uterus) performed when the patient consented only to a tubal ligation (clipping of the fallopian tubes for purposes of sterilization).

c.    Expert testimony creates an inference that negligence caused the injury, such as an expert general surgeon testifying that he has performed over 1000 appendectomies (removal of the appendix) and has never caused injury to a patient's liver. He also does not know of any of his surgeon colleagues having inflicted injury to a patient's liver during an appendectomy. The testimony would create an inference that injuring the liver in the course of an appendectomy is negligence.

The second element is discussed further in the section below. The third element requires the absence of contributory negligence from the plaintiff. The fourth element emphasizes that the defendant may defeat a res ipsa loquitur claim by producing evidence of a non-negligent scenario that would completely explain the plaintiff's injury and negate all possible inferences that negligence could have occurred.