What You'll Learn

  • The objective standard 2. Modified standards
  • The Learned Hand formula 4. Statutes and circumstantial proof
  • An exam method

Educational information only; not legal advice. This article is a general study aid and should be checked against current authority and course materials.

1. Start with the Correct Standard of Care

Ordinary adult Compared with a reasonably prudent person under similar circumstances. Personal inexperience or forgetfulness does not lower the standard. Physical disability Compared with a reasonable person with the same physical disability. Mental disability usually does not alter the ordinary standard.

Child Compared with a child of like age, intelligence, maturity, training, and experience, unless engaged in an adult or dangerous activity. Professional Compared with a reasonably competent member of the profession. Medical cases commonly require qualified expert testimony.

A sudden emergency is part of the circumstances, not a license to act carelessly. The doctrine does not help a defendant who created the emergency or reacted unreasonably to it.

2. Use the Available Methods of Proving Breach

The outlines organize breach proof around several recurring tools. None should be discussed mechanically. Explain why the tool fits the facts and what inference it permits.

Method What it asks Exam effect

Learned Hand formula Was the burden of precaution less than probability multiplied by gravity of loss (B < P x L)? Supports a reasonableness argument; it is not a mathematical prerequisite.

Industry custom What do actors in the field ordinarily do? Relevant but not conclusive; an entire industry can lag behind reasonable care.

Negligence per se Did an unexcused statutory violation harm a protected person in the protected way? May replace the ordinary breach inquiry, depending on the jurisdiction.

Res ipsa loquitur Is this an event that ordinarily does not happen without negligence and was the instrumentality tied to the defendant? Permits an inference when the plaintiff cannot identify the precise careless act.

Professional proof Did the defendant fall below the relevant professional standard? Usually requires expert testimony on standard and causation.

Key Takeaway

Ask whether the statute clearly states conduct, whether the plaintiff belongs to the protected class, whether the injury is the type the statute seeks to prevent, and whether the violation is excused. The outlines list excuses such as inability to comply, a confusing statute, an emergency not caused by the actor, or greater danger from compliance.

Res ipsa is an inference, not automatic victory

The event must ordinarily imply negligence, the instrumentality must have been within the defendant's control in the relevant sense, and the plaintiff must not have contributed. Most formulations allow, rather than compel, the jury to infer breach.

Custom can cut both ways

Compliance with custom supports reasonable care; departure may support breach. But the ultimate question remains what reasonable care required, not simply what others happened to do.

3. Match the Proof to the Facts

1 State the applicable reasonable-person or professional standard. 2 Define the foreseeable risk and the specific precaution allegedly omitted. 3 Use B < P x L to explain why the precaution was or was not reasonable. 4 Address custom or internal practices as evidence, not as the final rule. 5 If a safety statute applies, test protected class, protected harm, and excuse. 6 If the exact negligent act is unknown, test res ipsa loquitur and explain the permitted inference.

Key Takeaway

A grocery store has no inspection record for an aisle where a customer slips on milk. The plaintiff cannot prove who spilled it or exactly when. The absence of reasonable inspections may support constructive notice and breach. If the business method regularly creates the hazard, the mode-of-operation reasoning may reduce the need for specific notice.

Common Mistake

Do not say that a statute automatically creates liability. Even negligence per se leaves causation and damages to be proved, and the defendant may have a recognized excuse.

Primary Authorities

  • • Vaughan v. Menlove (objective reasonable-person standard).

  • • United States v. Carroll Towing Co. (B < P x L).

  • • Trimarco v. Klein (custom as evidence).

  • • Osborne v. McMasters and Martin v. Herzog (statutory violations).

  • • Byrne v. Boadle (res ipsa loquitur).

  • • Morrison v. MacNamara (professional standard of care).

Exam-ready conclusion

Breach is proved by a standard plus facts. Start with reasonable care, then use the Hand formula, custom, professional proof, negligence per se, or res ipsa only when those doctrines sharpen the analysis.