Res ipsa loquitur

"The thing speaks for itself" — some accidents do not happen without negligence, and the law lets a jury infer it.

It is the doctrine for cases where you cannot show exactly what went wrong, because the people who could explain it are the ones being sued. This is general information, not legal advice.

What it means

California puts it in the Evidence Code rather than leaving it to case law. It is a presumption affecting the burden of producing evidence — which is a narrower thing than it sounds, and worth being precise about.

On request, the court instructs the jury that if the facts supporting the doctrine are established, they may infer that the defendant's negligence caused the occurrence; and that they must find negligence only if, weighing all the evidence, they believe it more probable than not that the occurrence resulted from that negligence.

So it does not win a case on its own. It gets a case to a jury that would otherwise fail for want of a mechanism.

Where this is dealt with properly

This entry is the short answer. These pages own the subject.

• Premises liability claims
• The California injury claims process

Common questions

Does res ipsa mean I do not have to prove anything?

No. It lets a jury infer negligence from the nature of the accident rather than from direct evidence of what was done wrong. The jury still has to find it more probable than not.

Sources: Evid. Code, § 646 (res ipsa loquitur as a presumption affecting the burden of producing evidence; the instruction on request).