Res ipsa loquitur
To use res ipsa loquitur in the context of negligence, for example, the plaintiff must prove that:
- The harm would not ordinarily have occurred without someone's negligence
- The instrumentality of the harm was under the exclusive control of the defendant at the time of the likely negligent act
- The plaintiff did not contribute to the harm by his own negligence.
The principle of res ipsa loquitur was first put forth in the Byrne v. Boadle case of 1863. Byrne was struck by a barrel of flour falling from a second-story window. The court's presumption was that a barrel of flour falling out of a second-story window is itself sufficient evidence of negligence:
- We are all of opinion that the rule must be absolute to enter the verdict for the plaintiff. The learned counsel was quite right in saying that there are many accidents from which no presumption of negligence can arise, but I think it would be wrong to lay down as a rule that in no case can a presumption of negligence arise from the fact of an accident. Suppose in this case the barrel had rolled out of the warehouse and fallen on the plaintiff, how could he possibly ascertain from what cause it occurred? It is the duty of persons who keep barrels in a warehouse to take care that they do not roll out, and I think that such a case would, beyond all doubt, afford prima facie evidence of negligence. A barrel could not roll out of a warehouse without some negligence, and to say that a plaintiff who is injured by it must call witnesses from the warehouse to prove negligence seems to me preposterous.
- The present case upon the evidence comes to this, a man is passing in front of the premises of a dealer in flour, and there falls down upon him a barrel of flour. I think it apparent that the barrel was in the custody of the defendant who occupied the premises, and who is responsible for the acts of his servants who had the control of it; and in my opinion the fact of its falling is prima facie evidence of negligence, and the plaintiff who was injured by it is not bound to show that it could not fall without negligence, but if there are any facts inconsistent with negligence it is for the defendant to prove them.
- Chief Baron Pollock