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self-study / Torts

Apr. 21, 2023

Res Ipsa Loquitur: How presumptuous!

Allen P. Wilkinson


Allen is a widely published legal writer and bestselling author, and currently lives in Orange, California. He can be contacted at

Reza Torkzadeh

Founder and CEO, TorkLaw

11601 Wilshire Blvd Ste 500
Los Angeles , CA 90025

Phone: (310) 935-1111


Thomas Jefferson SOL; San Diego CA

Reza's latest book is "The Lawyer as CEO."

One of the first cases every law student reads in Torts class is Byrne v. Boadle ((Ex. 1863) 159 Eng. Rep. 299.), an old English case in which the plaintiff was walking along a public street minding his own business when a barrel of flour rolled out of the window of the warehouse above him and struck him on the head, causing serious injuries. Although two eyewitnesses saw the barrel hit the plaintiff, the plaintiff could not prove any specific act of negligence of the defendant that led to the barrel of flour rolling out of the window. Despite the lack of direct evidence showing exactly how, when, and why the defendant had been careless and was at fault, the plaintiff filed suit for negligence based upon the simple common sense that a barrel doesn’t just roll out of a window above a public walkway for no reason. There was no direct evidence of the defendant’s negligence, only circumstantial. Due to this lack of direct evidence as to how the barrel came to roll out of the window, the trial court found for the defendant.

The case was appealed to the Exchequer Court, which applied the doctrine of res ipsa loquitur for the first known time to hold the defendant liable. Writing for the court, Chief Baron Pollock stated: “There are certain cases of which it may be said res ipsa loquitur, and this seems one of them. . . . [¶] 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 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 shew that it could not fall without negligence, but if there are any facts inconsistent with negligence it is for the defendant to prove them.” (Byrne v. Boadle, supra, 159 Eng. Rep. 299, 300.)

Res ipsa loquitur – “the thing speaks for itself” – is a doctrine affecting the burden of producing evidence applicable to those kinds of accidents that are likely to have been caused by a defendant’s negligence. If applicable, the doctrine of res ipsa loquitur establishes a presumption of negligence requiring the defendant to come forward with evidence to disprove or explain it. (Baumgardner v. Yusuf (2006)144 Cal. App. 4th 1381, 1389.) When the doctrine of res ipsa loquitur applies, the presumed fact is that a proximate cause of the plaintiff’s injuries was some negligent conduct on the part of the defendant. (Elcome v. Chin (2003) 110 Cal. App. As 4th 310, 316.)

Res ipsa loquitur is a rule of evidence allowing an inference from the happening of the accident. It is based on a theory of “probability” where there is no direct evidence of the defendant’s conduct, permitting a common sense inference from the happening of the accident. The doctrine of res ipsa loquitur is designed to assist a plaintiff in establishing the existence of negligence after it is shown that a defendant was in control of the thing that produced the injury. (Gicking v. Kimberlin (1985) 170 Cal. App. 3d 73, 75; Moreno v. Sayre (1984) 162 Cal. App. 3d 116, 124.)

Three elements must be satisfied before the doctrine of res ipsa may be invoked:

The accident must be of a kind that ordinarily does not occur in the absence of someone’s negligence;

The accident was caused by an agency or instrumentality within the exclusive control of the defendant; and

The accident must not have been due to any voluntary action or contribution on the part of the plaintiff. (Brown v. Poway Unified School Dist. (1993) 4 Cal. 4th 820, 825-26; Newing v. Cheatham (1975) 15 Cal. 3d 351, 359; Ybarra v. Spangard (1944) 25 Cal. 2d 486, 489; Baumgardner v. Yusuf (2006) 144 Cal. App. 4th 1381, 1389.)

When all these prerequisites are met, the trier of fact is allowed to assume the existence of negligence unless the defendant introduces evidence to the contrary. (Blackwell v. Hurst (1996) 46 Cal. App. 4th 939, 943.)

The doctrine of res ipsa loquitur creates a presumption that the injury to the plaintiff was more probably than not the proximate result of negligence on the part of the defendant and shifts the burden to the defendant to prove the absence of negligence on his or her part. (Ybarra v. Spangard (1944) 25 Cal. 2d, 486, 490.) As the high court explained: “The question is one of probabilities and the doctrine ‘is applicable where the accident is of such a nature that it could be said, in the light of past experience, that it probably was the result of negligence by someone and that the defendant is probably the one responsible.’” (Shahinian v. McCormick (1963) 59 Cal. 2d 554, 559; Elcome v. Chin (2003) 110 Cal. App. 4th 310, 317.) The fact that a particular injury rarely occurs does not in itself justify an inference of negligence unless some other evidence indicates negligence. (Blackwell v. Hurst, supra, 46 Cal. App. 4th 939, 944.)

The doctrine of res ipsa loquitur is based upon a “common sense” inference of negligence from the mere happening of the incident itself. The rule is further justified by the fact that the chief evidence of the true cause, whether culpable or innocent, frequently is practically accessible to the defendant but inaccessible to the injured party. (Ybarra v. Spangard, supra, 25 Cal. 2d 486, 490.) In determining whether the accident is of a type which ordinarily does not occur in the absence of negligence, the court may consider common knowledge, the testimony of expert witnesses, and circumstances relating to the accident at issue. (Moreno v. Sayre (1984) 162 Cal. App. 3d 116, 123.)

In 1970, the judicial doctrine of res ipsa loquitur was codified as section 646 of the Evidence Code. Section 646, subd. (b) defines res ipsa as a presumption affecting the burden of producing evidence. A presumption affecting the burden of producing evidence requires the trier of fact to assume the existence of the presumed fact unless the defendant produces evidence to the contrary. (Sections 604 & 646, subd. (c).) The presumed fact in this context is that a proximate cause of the occurrence was some negligent conduct on the part of the defendant. (Section 646, subd. (c)(1).) If the defendant introduces evidence which would support a finding that he was not negligent or that any negligence on his part was not a proximate cause of the occurrence, the doctrine of res ipsa does not apply and the plaintiff must prove the defendant was negligent without regard to the presumption. In such a situation, the trier of fact is left to determine whether the defendant was negligent by weighing the evidence admitted at trial. (Sections 604, & 646, subd. (c)(2).

What the doctrine of res ipsa loquitur does is place the burden on the defendant to explain the accident: “In an integrated society where individuals become inevitably dependent upon others for the exercise of due care, where these relationships are closely interwoven with our daily living, the requirement for explanation is not too great a burden to impose upon those who wield the implements of injury and whose due care is vital to life itself.” (Cho v. Kempler (1960) 177 Cal. App. 2d 342, 349.)

Res ipsa does not apply where the cause of the accident is merely speculative or it is at least equally probable that the accident was caused by some fault or event (such as an act of God) for which the defendant was not liable. (Zentz v. Coca Cola Bottling Co. (1952) 39 Cal. 2d 436, 443.) Where the only reasonably probable causes of injury are traced solely to the conduct of the defendant and a third party, res ipsa does not apply unless the defendant is legally responsible for the third party’s negligence, since the negligence of the latter is an equally probable cause of the accident. This requirement protects the defendant from being held liable for someone else’s negligence. (Giking v. Kimberlin (1985) 170 Cal. App. 73; Moreno v. Sayre (1984) 162 Cal. App. 3d 119; Pappas v. Carson (1975) 11 Cal. App. 3d 261.)

In cases involving multiple defendants or causes, the plaintiff is required only to eliminate the probability that the accident was caused by someone other than the defendants. Where multiple defendants had control over the injury-producing instrumentality at one time or another, it is up to the defendant to explain how the injury came about and that he or she was not to blame. It need not be concluded that the defendant’s negligence is the only explanation of the accident, but merely the most probable one. (Newing v. Cheatham, supra, 15 Cal. 3d 351, 360.)

Res ipsa loquitur is fairly often raised in medical malpractice cases. Where a plaintiff receives unusual injuries while unconscious and in the course of medical treatment, all those defendants who had any control over his or her body or the instrumentality which might have caused the injuries may properly be called upon to meet the inference of negligence by giving an explanation of their conduct. The test for exclusive control has become one of right of control rather than actual control. (Ybarra v. Spangard, supra, 25 Cal. 2d 25 Cal. 2d 486, 494; Baumgardner v. Yusuf, supra, 144 Cal. App. 4th 1381, 1392.)

One example which occurs more frequently than it should involves a surgeon or other health care provider leaving a sponge, a medical instrument, or other foreign object in the patient which is not for treatment or therapeutic purposes. Injuries to other, healthy parts of the body may also be appropriate for the application of res ipsa. For example, res ipsa has been properly applied in cases where the patient suffered a shoulder injury while undergoing an appendectomy, a broken rib during a kidney operation, reading an x-ray backward so that a healthy kidney is removed or the wrong limb is amputated, and a torn sternum cartilage and fractured rib, as well as the aggravation of a pre-existing hernia caused by a chiropractor during the manipulation of the patient’s upper back.

Medical malpractice cases involve special considerations, especially where the patient is unconscious at the time of the negligent act or omission. Thus, as the Supreme Court stated in Ybarra v. Spangard: “It should be enough that the plaintiff can show an injury resulting from an external force applied while he lay unconscious in the hospital; this is as clear a case of identification of the instrumentality as the plaintiff may ever be able to make.” (Ybarra v. Spangard supra, 25 Cal. 2d 486, 492-93.)

As a general rule, res ipsa loquitur does not apply to slip and fall cases as they are not so likely to be the result of negligence to justify a presumption to that effect. (Brown v. Poway Unified School Dist. (1993) 4 Cal. 4th 820, 826-27 [collection of cases at fn. 2].) There are many accidents which, as a matter of common knowledge, occur frequently enough without anyone’s fault. An ordinary slip and fall will not itself justify the conclusion that negligence is the most likely explanation; and to such events res ipsa loquitur does not apply. (Brown, supra, 4 Cal. 4th 820, 826.)

In a case in which the defendant was injured when she fell to the floor upon stepping on a piece of chalk, the court stated: “The burden is on the plaintiff to prove every essential fact on which she relies. This burden is not met merely by proof that the plaintiff invitee stepped on something while on the invitor’s premises and thereby was caused to fall and receive injuries, for no inference of negligence arises based simply upon proof of the fall on the owner’s floor. The doctrine of res ipsa loquitur is not applicable to such cases.” (Oldenburg v. Sears, Roebuck & Co. (1957) 152 Cal. App. 2d 773, 741.)

Res ipsa loquitur is not an independent cause of action; it is an evidentiary rule for determining whether circumstantial evidence of negligence is sufficient. Because it is a rule concerning the presentation of evidence and is not an independent ground of liability, a plaintiff cannot invoke the doctrine of res ipsa loquitur as a theory of liability. (Gicking v. Kimberlin (1985) 170 Cal. App. 3d 73, 78; Moreno v. Sayre (1984) 162 Cal. App. 3d 124, 125; Dorswitt v. Wison (1942) 51 Cal. App. 2d 625.) Since it is not a theory of liability, res ipsa does not impose a duty of care and is therefore not a proper ground for demurrer.

If evidence is produced that would support a finding that the defendant was not negligent or that any negligence on his part was not a proximate cause of the accident, the presumption of the doctrine vanishes. The mere introduction of evidence that would be sufficient to sustain a finding of the nonexistence of the presumed fact causes the presumption to disappear as a matter of law. When the presumptive effect vanishes, it is the plaintiff’s burden to introduce actual evidence that would show that the defendant is negligent and that such negligence was the proximate cause of the accident. Even though the presumptive effect of the doctrine vanishes, the jury may still be able to draw an inference that the accident was caused by the defendant’s lack of due care from the facts that give rise to the presumption. (Howe v. Seven Forty Two Co., Inc., supra, 189 Cal. App. 4th 1155, 1163-64.)


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