The plaintiff in a tort suit, as in any other, has the burden of proving his allegations.
He must show that the defendant took the actions complained of as negligent, demonstrate the circumstances that make the actions negligent, and prove the occurrence and extent of injury. Factual issues are for the jury to resolve. Since it is frequently difficult to make out the requisite proof, the law allows certain presumptions and rules of evidence that ease the plaintiff’s task, on the ground that without them substantial injustice would be done. One important rule goes by the Latin phrase res ipsa loquitur, meaning “the thing speaks for itself.” The best evidence is always the most direct evidence: an eyewitness account of the acts in question. But eyewitnesses are often unavailable, and in any event they frequently cannot testify directly to the reasonableness of someone’s conduct, which inevitably can only be inferred from the circumstances.
In many cases, therefore, circumstantial evidence (evidence that is indirect) will be the only evidence or will constitute the bulk of the evidence. Circumstantial evidence can often be quite telling: though no one saw anyone leave the building, muddy footprints tracing a path along the sidewalk are fairly conclusive. Res ipsa loquitur is a rule of circumstantial evidence that permits the jury to draw an inference of negligence. A common statement of the rule is the following: “There must be reasonable evidence of negligence but where the thing is shown to be under the management of the defendant or his servants, and the accident is such as in the ordinary course of things does not happen if those who have the management use proper care, it affords reasonable evidence, in the absence of explanation by the defendants, that the accident arose from want of care. 1
If a barrel of flour rolls out of a factory window and hits someone, or a soda bottle explodes, or an airplane crashes, courts in every state permit juries to conclude, in the absence of contrary explanations by the defendants, that there was negligence. The plaintiff is not put to the impossible task of explaining precisely how the accident occurred. A defendant can always offer evidence that he acted reasonably—for example, that the flour barrel was securely fastened and that a bolt of lightning, for which he was not responsible, broke its bands, causing it to roll out the window. But testimony by the factory employees that they secured the barrel, in the absence of any further explanation, will not usually serve to rebut the inference. That the defendant was negligent does not conclude the inquiry or automatically entitle the plaintiff to a judgment. Tort law provides the defendant with several excuses, some of which are discussed briefly in the next section.