Res Ipsa Loquitur

[Latin, The thing speaks for itself.] A rebuttable presumption or inference that the defendant was negligent, which arises upon proof that the instrumentality or condition causing the injury was in the defendant's exclusive control and that the accident was one that ordinarily does not occur in the absence of NEGLIGENCE.

Res ipsa loquitur, or res ipsa, as it is commonly called, is really a rule of evidence, not a rule of SUBSTANTIVE LAW.

Negligence is conduct that falls below the standard established by law for the protection of others against an unreasonable risk of harm. In order to prevail in a negligence action, a plaintiff must establish by a PREPONDERANCE OF EVIDENCE that the defendant's conduct was unreasonable in light of the particular situation and that such conduct caused the plaintiff's injury. The mere fact that an accident or an injury has occurred, with nothing more, is not evidence of negligence. There must be evidence that negligence caused the event. Such evidence can consist of direct testimony by eyewitnesses who observed the defendant's unreasonable conduct and its injurious result.

Negligence can also be established by CIRCUMSTANTIAL EVIDENCE when no direct evidence exists. Circumstantial evidence is evidence of one recognized fact or set of facts from which the fact to be determined can be reasonably inferred because it is the logical conclusion that can be drawn from all the known facts. For example, skid marks at the scene of an accident are circumstantial evidence that a car was driven at an excessive speed. The reasoning process must be based upon the facts offered as evidence, together with a sufficient background of human experience, to justify the conclusion. Evidence that merely suggests the possibility of negligence is insufficient, since negligence must appear more likely than not to have occurred. This inference must cover all the necessary elements of negligence: that the defendant owed the plaintiff a duty, which the defendant violated by failing to act according to the required standard of conduct, and that such negligent conduct injured the plaintiff.

Res ipsa loquitur is one form of circumstantial evidence that permits a reasonable person to surmise that the most PROBABLE CAUSE of an accident was the defendant's negligence. This concept was first advanced in 1863 in a case in which a barrel of flour rolled out of a warehouse window and fell upon a passing pedestrian. Res ipsa loquitur was the reasonable conclusion because, under the circumstances, the defendant was probably culpable since no other explanation was likely. The concept was rapidly applied to cases involving injuries to passengers caused by carriers, such as railroads, which were required to prove they had not been negligent. Res ipsa loquitur, as it is in the early 2000s applied by nearly all of the 50 states, deals with the sufficiency of circumstantial evidence and, as in some states, affects the BURDEN OF PROOF in negligence cases.