Byrne v. Boadle 2 H. & C. 722, 159 Eng. Rep. 299 (Exch. 1863) Byrne was walking down the street when he was bonked on the head by a barrel of flour. Byrne testified at trial that he never saw the barrel coming and didn't know what happened. Coincidentally, Byrne was standing in front of Boadle's two-story tall flour shop when the barrel fell on him. At Trial, Boadle argued that there were no witnesses to the barrel's falling, and so there was no evidence that any negligence occurred. Boadle argued that the only evidence that existed was circumstantial evidence, which is generally inadmissible. There was no evidence of an untaken precaution. That means that no one saw any Boadle employee do anything that was negligent (like leaving the window open and letting a barrel roll out). Therefore, how could they possibly be liable? The Trial Court found for Byrne. The Trial Court found that the very fact that an accident occurred is evidence that somebody somewhere was negligent. This argument is known as res ipsa loquitur. ("The thing speaks for itself"). The Court said, "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." Three aspects required to use res ipsa loquitur: 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. In the case of Valley Properties Limited Partnership v. Steadman's Hardware Inc. (251 Mont. 242, 842 P.2d 250 (1992)), it was stated that res ipsa loquitur requires that: The event is of the kind which does not ordinarily occur in the absence of negligence. Other responsible causes, including the conduct of the plaintiff or others, are sufficiently eliminated by the evidence. The indicated negligence is within the scope of the defendant's duty to the plaintiff. Going back to the risk-utility formula one could say that there was something that Boadle could have done, at some cost, that would have prevented the accident, and the cost of that precautionary measure would be less than the potential liability of the accident.