Negligence - Rules of conduct derived from statutes and custom

Learning Outcomes

After reading this article, you will be able to identify when statutory rules and industry custom set the standard of care in negligence cases. You will understand the doctrine of negligence per se, the evidentiary role of custom, and how these rules affect breach analysis. You will be able to apply these principles to MBE-style questions and spot common pitfalls.

MBE Syllabus

For MBE, you are required to understand how statutes and custom influence the standard of care in negligence. This includes:

  • Recognizing when a statute sets the standard of care (negligence per se).
  • Knowing the requirements for applying negligence per se.
  • Understanding the evidentiary value of custom and industry practice.
  • Distinguishing between statutory rules, custom, and the reasonable person standard.
  • Applying these concepts to breach and causation analysis in negligence.

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

  1. When does violation of a safety statute automatically establish breach of duty in a negligence case?
    1. Always, if the statute was violated.
    2. Only if the plaintiff is in the class the statute was designed to protect and the harm is the type the statute was meant to prevent.
    3. Only if the defendant acted intentionally.
    4. Never; statutes are only evidence of negligence.
  2. Evidence that a defendant complied with industry custom is:
    1. Conclusive proof that the defendant was not negligent.
    2. Irrelevant to the standard of care.
    3. Admissible but not conclusive on breach of duty.
    4. Required for all negligence cases.
  3. Which of the following is NOT a valid excuse for violating a safety statute in a negligence case?
    1. Compliance was impossible under the circumstances.
    2. Compliance would have caused greater harm.
    3. The defendant was unaware of the statute.
    4. The defendant was physically unable to comply.

Introduction

In negligence law, the standard of care is usually that of a reasonable person. However, statutes and industry custom can alter or clarify what conduct is required. When a statute prescribes specific conduct, courts may treat violation of that statute as automatic breach of duty—this is the doctrine of negligence per se. Custom, on the other hand, is evidence of what is reasonable but is not controlling. Understanding when and how these rules apply is essential for MBE success.

Key Term: Negligence Per Se
The doctrine that violation of a safety statute or regulation constitutes automatic breach of duty in negligence if certain requirements are met.

Key Term: Custom (in Negligence)
Evidence of the usual practice in an industry or community, used to show what is reasonable conduct under the circumstances.

Statutory Rules as Standards of Care: Negligence Per Se

When a statute or regulation sets a specific standard of conduct, courts may adopt that standard as the required duty in a negligence case. If the defendant violates the statute, and the violation causes the plaintiff's harm, the breach element is satisfied as a matter of law—unless the violation is excused.

Requirements for Negligence Per Se

Negligence per se applies only if:

  1. The statute or regulation sets a clear standard of conduct.
  2. The plaintiff is in the class of persons the statute was designed to protect.
  3. The harm suffered is the type the statute was intended to prevent.
  4. The violation was not excused.

If all requirements are met, the statute replaces the reasonable person standard for breach.

Key Term: Class of Persons
The group the legislature intended to protect by enacting the statute.

Key Term: Type of Harm
The kind of injury the statute was meant to prevent.

Excuses for Statutory Violation

A defendant may avoid negligence per se if the violation is excused. Common excuses include:

  • Compliance was impossible or would have caused greater harm.
  • The defendant was physically unable to comply.
  • The statute was too vague or ambiguous.
  • Emergency circumstances made compliance unreasonable.

Ignorance of the law is generally not an excuse.

Effect of Compliance

Compliance with a statute does not guarantee that the defendant was not negligent. A reasonable person may need to take additional precautions if circumstances require it.

Worked Example 1.1

A state law requires all store owners to shovel snow from their sidewalks within 6 hours of a snowfall. A store owner fails to do so, and a customer slips and is injured. The customer sues for negligence. Does the statute set the standard of care?

Answer: Yes. The statute is clear, the customer is in the protected class (pedestrians), and the harm (slipping on snow) is the type the statute aims to prevent. The store owner's violation is negligence per se unless an excuse applies.

Worked Example 1.2

A driver swerves to avoid hitting a child and crosses a double yellow line, violating a traffic law. The driver collides with another car. Is the driver automatically negligent per se?

Answer: Not necessarily. If compliance with the statute (staying in the lane) would have caused greater harm (hitting the child), the violation may be excused, and negligence per se does not apply.

Exam Warning

On the MBE, do not apply negligence per se unless the statute is specific, the plaintiff is in the protected class, and the harm is of the type the statute was meant to prevent. If any element is missing, the statute is only evidence of negligence, not conclusive.

Custom and Industry Practice

Custom refers to the usual way things are done in a particular industry or community. Evidence of custom is admissible to show what is reasonable, but it is not conclusive. A party may be found negligent even if they complied with custom, or not negligent even if they departed from it.

Key Term: Industry Custom
The established practice or method commonly followed by members of a trade or profession.

Role of Custom in Negligence

  • Compliance with custom is evidence that the defendant acted reasonably, but it does not guarantee a finding of no negligence.
  • Departure from custom is evidence of negligence, but it is not automatic breach.
  • In professional malpractice cases (e.g., doctors, lawyers), compliance with custom is usually required to avoid liability.

Worked Example 1.3

A hotel uses a cleaning chemical in the same way as all other hotels in the area. A guest is injured because the chemical was not diluted. The guest sues for negligence. Is the hotel's compliance with custom a defense?

Answer: No. Compliance with custom is evidence of reasonable care, but if the custom itself is unsafe, the hotel may still be found negligent.

Revision Tip

Always check whether a statute or custom sets the standard of care, but remember: statutes can create automatic breach (if all elements are met), while custom is only evidence, not a rule.

Summary

  • Statutes may set the standard of care in negligence cases (negligence per se).
  • Negligence per se applies only if the statute is clear, the plaintiff is in the protected class, and the harm is of the type the statute was meant to prevent.
  • Excuses may prevent negligence per se from applying.
  • Compliance with a statute does not guarantee due care.
  • Custom is evidence of what is reasonable, but is not conclusive.
  • In professional malpractice, custom is often controlling.

Key Point Checklist

This article has covered the following key knowledge points:

  • Statutory rules can set the standard of care (negligence per se) if specific requirements are met.
  • Negligence per se requires a clear statute, protected class, and type of harm.
  • Excuses (impossibility, greater harm, emergency) may prevent negligence per se.
  • Compliance with a statute does not guarantee reasonableness.
  • Custom is admissible evidence of reasonable care but is not controlling.
  • Professional malpractice often requires compliance with custom.

Key Terms and Concepts

  • Negligence Per Se
  • Custom (in Negligence)
  • Class of Persons
  • Type of Harm
  • Industry Custom
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