In some negligence cases, direct evidence of how something went wrong is unavailable. CACI No. 417 addresses those situations by allowing juries to infer negligence from the nature of the accident itself under the doctrine known as res ipsa loquitur.
Translated from Latin, res ipsa loquitur means “the thing speaks for itself.”
What Is CACI No. 417?
CACI No. 417 applies when a plaintiff cannot point to a specific negligent act but can show that the injury would not ordinarily occur without negligence, that the defendant controlled the instrumentality that caused the harm, and that the plaintiff did not cause the event.
This instruction does not automatically establish liability, but it permits jurors to infer negligence when the circumstances justify it.
Legal Foundation for Res Ipsa Loquitur
California recognizes res ipsa loquitur as a special negligence doctrine designed to prevent defendants from escaping liability simply because the precise mechanism of negligence is unknown or hidden.
The doctrine shifts the focus from how the negligence occurred to whether, as a matter of common experience, the injury likely resulted from someone’s lack of reasonable care.
Full Text of CACI No. 417
CACI No. 417. Special Doctrines: Res Ipsa Loquitur
[Name of plaintiff] may prove that [name of defendant]’s negligence caused [his/her/nonbinary pronoun] harm if [he/she/nonbinary pronoun] proves all of the following:
- That [name of plaintiff]’s harm ordinarily would not have happened unless someone was negligent;
- That the harm was caused by something that only [name of defendant] controlled; and
- That [name of plaintiff]’s voluntary actions did not cause or contribute to the event[s] that harmed [him/her/nonbinary pronoun].
If you decide that [name of plaintiff] did not prove one or more of these three things, you must decide whether [name of defendant] was negligent in light of the other instructions I have read.
If you decide that [name of plaintiff] proved all of these three things, you may, but are not required to, find that [name of defendant] was negligent or that [name of defendant]’s negligence was a substantial factor in causing [name of plaintiff]’s harm, or both.
[Name of defendant] contends that [he/she/nonbinary pronoun/it] was not negligent or that [his/her/nonbinary pronoun/its] negligence, if any, did not cause [name of plaintiff] harm. If after weighing all of the evidence, you believe that it is more probable than not that [name of defendant] was negligent and that [his/her/nonbinary pronoun] negligence was a substantial factor in causing [name of plaintiff]’s harm, you must decide in favor of [name of plaintiff]. Otherwise, you must decide in favor of [name of defendant].
New September 2003; Revised June 2011, December 2011
How Juries Apply Res Ipsa Loquitur
Under CACI 417, jurors ask three threshold questions:
- Does the type of harm usually occur only when someone is negligent?
- Was the instrumentality that caused the harm under the defendant’s control?
- Did the plaintiff avoid contributing to the event?
If all three are proven, jurors are permitted—but not required—to infer negligence. The defendant may still rebut that inference with evidence of reasonable care or alternative explanations.
Illustrative Example
A surgical instrument is left inside a patient during an operation. The patient cannot identify which specific act caused the error, but such an injury ordinarily does not occur without negligence and the surgical team controlled the instruments. Under CACI 417, a jury may infer negligence based on the circumstances alone.
Practical Considerations in Res Ipsa Cases
These cases often involve:
- Exclusive control over equipment or premises
- Injuries that defy ordinary, non-negligent explanation
- Situations where evidence is primarily in the defendant’s possession
Res ipsa loquitur is especially powerful when common sense strongly suggests negligence, even if direct proof is unavailable.
Speak With a Negligence Lawyer
If you were injured under circumstances that should not have occurred absent negligence, CACI No. 417 may apply. WIN Injury & Accident Trial Lawyers can evaluate whether the doctrine of res ipsa loquitur strengthens your negligence claim.
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