Black-letter propositions
- 01
Risk balancing considers probability and gravity of harm against burden and utility of precautions.
- 02
Industry custom is relevant but not conclusive; a whole industry can be negligent.
- 03
Res ipsa loquitur permits an inference when the event ordinarily does not happen without negligence, responsible causes including plaintiff are sufficiently eliminated, and negligence falls within defendant's duty.
- 04
Multiple defendants can sometimes be addressed through alternative liability when all acted negligently, one caused harm, and uncertainty is not the plaintiff's fault.
- 05
Mode-of-operation and recurring-risk rules may affect premises proof under local law.
Use this attack sequence under time
Frame the issue
State the untaken precaution.
Resolve the next checkpoint
Compare risk and burden using facts.
Resolve the next checkpoint
Use custom or statute as evidence where appropriate.
Resolve the next checkpoint
If no direct proof, test every res ipsa element.
Finish the conclusion
Address allocation among multiple actors.
Common wrong turns
- An accident alone does not prove negligence.
- Res ipsa usually creates an inference, not automatic liability.
- Exclusive control is functional and need not mean literal uninterrupted custody.
Worked example
A surgical instrument is left inside an unconscious patient after a team procedure.
This ordinarily does not occur without negligence, the patient did not contribute, and the responsible actors controlled the process. Res ipsa or team-liability principles can permit an inference.
Practice this topic
Breach tests
Cornell says some courts use the Hand Formula to test breach: if the burden of precautions is less than the probability of loss times its severity, the defendant breached the duty. It also lists factors for lack of reasonable care: the foreseeable likelihood of harm, the foreseeable severity and the burden of precautions. Negligence per se means a defendant who violates a statute or regulation without excuse is negligent as a matter of law, so the plaintiff need only prove cause in fact and proximate cause.
Under Restatement (Third) section 14 as Cornell describes it, the statute must protect against the type of harm and the plaintiff must be within the protected class. Exceptions include an unclear statute, reasonable attempts to comply and noncompliance causing less harm.
Res ipsa loquitur and multiple actors
Cornell describes res ipsa loquitur as a principle that lets plaintiffs meet their burden with circumstantial evidence. The plaintiff proves the incident is of a type that does not generally happen without negligence, that it was caused by an instrumentality solely in the defendant's control, and that the plaintiff did not contribute to the cause. That creates a rebuttable presumption of negligence.
When two or more parties are jointly and severally liable, each is independently liable for the full extent of the injuries, and the plaintiff may collect the full value from any one of them, who may seek contribution.
Frequently asked questions
What is the controlling rule for risk balancing, custom, res ipsa, and multiple actors?+
Breach requires a specific unreasonable precaution failure or a justified circumstantial inference such as res ipsa loquitur.
What is the Hand Formula?+
A breach test: if the burden of precautions is less than the probability of loss multiplied by its severity, the defendant breached the duty.
What is negligence per se?+
A violation of a statute or regulation without excuse is negligent as a matter of law, leaving only cause in fact and proximate cause to prove, per Cornell.
What must a plaintiff show for res ipsa loquitur?+
That the incident does not generally happen without negligence, was caused by an instrumentality solely in the defendant's control, and the plaintiff did not contribute.
What does res ipsa loquitur create?+
A rebuttable presumption of negligence, which the defendant may try to rebut, according to Cornell's summary of the doctrine.
What is joint and several liability?+
Each of two or more liable parties is independently liable for the full extent of the injuries, and the plaintiff may collect the whole judgment from any one.