Negligence - Rules of conduct derived from statutes and cust...

Learning Outcomes

This article explains how statutory rules and industry custom shape the standard of care in negligence for MBE-style questions, including:

• Identifying when a statute, regulation, or ordinance supplies the civil standard of care and when it is merely evidence of negligence under the reasonable person test.
• Applying the protected class / type of harm framework to determine whether negligence per se is available on given fact patterns.
• Distinguishing licensing or administrative statutes from true safety statutes and evaluating their evidentiary significance.
• Evaluating common excuses for statutory violations—impossibility, greater danger, emergency, and lack of knowledge of triggering facts—and predicting whether courts will treat the violation as negligence per se.
• Assessing how statutory compliance or noncompliance affects breach, actual cause, and proximate cause, as well as available defenses and damages.
• Using statutory violations by plaintiffs as contributory or comparative negligence per se and understanding their effect on recovery in different negligence regimes.
• Using evidence of custom and professional practice to argue both for and against breach, and recognizing when professional custom effectively defines the standard of care.
• Resolving conflicts between statutory standards, custom, and the general reasonable person benchmark to reach a defensible exam answer.

MBE Syllabus

For the MBE, you are required to understand how statutes and custom influence the standard of care in negligence, with a focus on the following syllabus points:

• Recognizing when a statute sets the standard of care (negligence per se).
• Knowing the requirements for applying negligence per se.
• Understanding when a statute is only evidence of negligence.
• Identifying valid excuses for statutory violations.
• 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.
• Using statutory and custom evidence on both plaintiff and defendant sides (including contributory/comparative 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 under the circumstances. But two other sources often shape what “reasonable care” requires:

• Statutes and regulations, which can set specific rules of conduct.
• Industry or community custom, which reflects how actors in similar situations typically behave.

When a statute prescribes particular conduct, courts may adopt that requirement as the civil standard of care. If the defendant violates such a statute and the violation causes the plaintiff’s harm, the breach element can be satisfied as a matter of law. This is the doctrine of negligence per se.

Custom, by contrast, almost never has this automatic effect. It is evidence of what is reasonable, but it does not control the outcome. A jury may find conduct unreasonable even if it complies with custom, or reasonable even if it departs from custom.

On the MBE, you will frequently see:

• A fact pattern that quotes or summarizes a statute or ordinance.
• A description of how “everyone in the industry” does something.

You must decide whether that statute or practice conclusively defines the standard of care or is merely evidence bearing on breach.

Key Term: Negligence Per Se
The doctrine that violation of a statute or regulation that sets a specific standard of conduct constitutes breach of duty in negligence, if all requirements for using the statute as the standard of care are met.

Key Term: Custom (in Negligence)
Evidence of the usual practice in an industry or community, offered to show what is reasonable conduct under the circumstances, but not itself a binding rule of conduct.

Key Term: Statutory Standard of Care
A duty of care defined by a statute or regulation, which a court adopts as the measure of reasonable conduct in a negligence case.

Statutory Rules as Standards of Care: Negligence Per Se

When a legislature or agency enacts a safety rule—“drivers must stop at red lights,” “store owners must clear snow from sidewalks within six hours,” “contractors must install guardrails”—that rule can supply the civil standard of care in a negligence action.

If a court adopts the statute as the standard of care and the defendant unreasonably fails to comply, breach is established without asking what an ordinary reasonable person would have done. The jury still decides causation and damages, but it does not weigh reasonableness independently.

Key Term: Statutory Standard of Care
A legislative or regulatory command that the court uses in place of the generic reasonable person standard to determine duty and breach.

Requirements for Negligence Per Se

Negligence per se is not automatic whenever a statute is violated. Most jurisdictions follow a structured test:

1. The statute or regulation sets a clear standard of conduct.

   • It must tell actors what to do or not do in specific terms (e.g., “do not drive over 55 mph,” “install smoke detectors in each unit”).
   • Vague commands like “drive carefully” or “maintain premises in good repair” usually do not qualify as statutory standards for negligence per se.

2. The plaintiff is in the class of persons the statute was designed to protect.

   • Ask why the legislature enacted the statute and whose safety it had in mind.

3. The harm suffered is the type of harm the statute was intended to prevent.

   • The statute must be aimed at preventing the kind of injury that occurred.

4. The violation was unexcused.

   • If the defendant has a legally sufficient excuse, the violation will not be treated as negligence per se.

Plaintiff still must prove actual cause, proximate cause, and damages. Negligence per se only addresses the duty/breach elements.

Key Term: Class of Persons
The group the legislature intended to protect by enacting the statute (e.g., pedestrians, tenants, consumers of a product).

Key Term: Type of Harm
The kind of injury—such as fall injuries, burns, or collisions—that the statute was meant to prevent.

Statutes That Can Be Used

For MBE purposes, the doctrine can apply to:

• Criminal statutes (e.g., DUI laws, speed limits).
• Administrative regulations (e.g., OSHA workplace rules).
• Municipal ordinances (e.g., snow-removal or building codes).

The fact that a statute is criminal does not prevent it from setting a civil standard of care.

If any of the four requirements is missing, the statute does not supply the standard of care; instead, it is just evidence that may support or undercut a finding of breach under the ordinary reasonable person standard.

Excuses for Statutory Violation

Even when the statute is clear and covers the plaintiff and the type of harm, a defendant may avoid negligence per se by showing a legally recognized excuse. Common excuses include:

• Compliance was impossible under the circumstances (e.g., brakes failed without warning despite reasonable maintenance).
• Compliance would have created a greater risk of harm (sometimes called the “greater danger” exception).
• The defendant was physically unable to comply (e.g., sudden medical emergency).
• The defendant did not know and could not reasonably discover the facts that made the statute applicable (e.g., an unknown headlight failure).
• The statute was too vague or ambiguous to give fair notice of the required conduct.
• Emergency circumstances made literal compliance unreasonable (e.g., swerving into the opposing lane to avoid a child).

Ignorance of the existence of the law itself (“I didn’t know there was a speed limit”) is generally not an excuse.

Key Term: Excused Violation
A statutory violation that does not amount to negligence per se because circumstances make compliance impossible, more dangerous, or otherwise unreasonable, even for a reasonable person.

For exam purposes, watch for facts that show:

• The violation was conscious and voluntary (more likely negligence per se).
• The violation was the product of an unforeseeable incapacity or emergency (more likely excused).

Effect of Compliance

Compliance with a statute does not guarantee that the defendant exercised reasonable care. A reasonable person might need to take additional precautions beyond the statutory minimum when circumstances warrant it.

Examples:

• A driver going 55 mph (the speed limit) in dense fog may still be negligent for not slowing down.
• A landlord who meets the building code but knows about a particular hazard might still be negligent for not addressing that hazard.

On the other hand, compliance is strong evidence that the defendant acted reasonably; it does not automatically resolve breach, but it is persuasive.

Key Term: Statutory Standard of Care
(revisited)
Statutes often set minimum safety requirements; breach may still be found when reasonable care required more than the statute demanded.

Statutory Violations by Plaintiffs

A plaintiff’s own violation of a safety statute may constitute contributory negligence per se (or comparative negligence, in a comparative fault jurisdiction) if:

• The statute was intended to protect persons like the plaintiff from their own risky behavior, and
• The plaintiff’s violation contributed to the harm.

On the MBE, this typically reduces recovery under comparative negligence or bars it in a strict contributory negligence jurisdiction, unless the statute was designed to protect the plaintiff’s class even against their own negligence (e.g., certain child labor or worker-safety statutes).

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 and specific, pedestrians like the customer are in the protected class, and slip-and-fall injuries from snow and ice are the type of harm the statute aims to prevent. If the store has no valid excuse, the violation is negligence per se as to duty and breach. The customer must still prove causation and damages.

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. The traffic law clearly sets a standard of conduct, and the other driver is within the protected class. But if staying in the lane would likely have caused greater harm (hitting the child), the violation may be excused. In that case, negligence per se does not apply; the factfinder evaluates the driver’s conduct under the ordinary reasonable person standard in an emergency.

Worked Example 1.3

A statute makes it a misdemeanor to drive a taxi without a city taxi license. A licensed driver negligently runs a red light and injures a pedestrian. The taxi company had failed to obtain the city taxi license. The pedestrian sues and argues negligence per se based on the licensing statute. Does the licensing violation establish breach?

Answer:
No. The licensing statute is primarily administrative—it regulates who may operate taxis, not how they must be driven. The harm (being hit by a taxi running a red light) is caused by negligent driving, not by the absence of the license. The red-light violation may be negligence per se if the relevant traffic statute is satisfied, but the taxi licensing violation is, at most, weak evidence of negligence and does not itself set the standard of care for this harm.

Worked Example 1.4

A state statute requires homeowners to install fire alarms in every bedroom to protect sleeping occupants from fire-related injury. A visitor trips over loose carpet in a hallway and breaks his arm. The homeowner never installed fire alarms. The visitor sues for negligence and invokes the fire-alarm statute. Can the visitor use negligence per se?

Answer:
No. Although the statute sets a clear standard, the visitor is not suffering the type of harm the statute was designed to prevent (fire-related injury to sleeping occupants), and his fall has no causal connection to the absence of fire alarms. The statute does not supply the standard of care for this claim; at most, it is irrelevant or marginal evidence and should not be used for negligence per se.

Worked Example 1.5

A pedestrian crosses a street outside of a crosswalk, in violation of a jaywalking ordinance, and is struck by a speeding driver who is also violating the speed limit statute. The pedestrian sues the driver. How do the statutes affect the analysis?

Answer:
The driver’s violation of the speed limit statute is negligence per se: the pedestrian is within the protected class and collision injuries are the type of harm the speed statute aims to prevent. The pedestrian’s violation of the jaywalking ordinance is also negligence per se as to her own duty of care, because she is among those the jaywalking rule is designed to protect, and her conduct increased the risk of exactly this type of harm. In a comparative negligence jurisdiction, her statutory violation will reduce her recovery in proportion to her fault. In a pure contributory negligence jurisdiction, her negligence per se may bar recovery altogether, unless an exception (such as last clear chance) applies.

Exam Warning

On the MBE, do not apply negligence per se unless:

• The statute sets a specific standard of conduct.
• The plaintiff is in the protected class.
• The harm is the type the statute aims to prevent.
• The violation is unexcused and causal.

If any of these are missing, treat the statute as evidence of negligence, not automatic breach.

Custom and Industry Practice

Custom refers to the usual way things are done in a particular industry, trade, or community—what is ordinary practice among similarly situated actors.

Key Term: Industry Custom
The established practice or method commonly followed by members of a trade, profession, or industry, offered to show what level of care is typical in that field.

Custom plays two main roles:

• It helps the factfinder decide what precautions a reasonable person in that position would take.
• In some professional malpractice contexts, it almost defines the standard of care.

But custom is not conclusive in ordinary negligence cases:

• A party may be found negligent even if it complied with custom.
• A party may be found not negligent even if it departed from custom.

Role of Custom in Negligence

• Compliance with custom is evidence for the defendant:

  • Suggests that the defendant acted as most reasonable actors in that field act.
  • But if the custom itself is unreasonable (outdated, unsafe, or driven by cost-saving rather than safety), the jury can still find breach.

• Departure from custom is evidence for the plaintiff:

  • Suggests that the defendant failed to use precautions that others in the field regard as necessary.
  • But the defendant can argue that the custom is unnecessarily strict or inapplicable to these facts.

• Professional malpractice:

  • For doctors, lawyers, accountants, and similar professionals, the standard of care is usually:
    “The level of skill and knowledge ordinarily possessed by members of that profession in good standing.”
  • This is essentially a custom-based standard; failure to follow professional custom is usually treated as breach, absent compelling justification.

Key Term: Custom (in Negligence)
(revisited)
Evidence of typical conduct in similar circumstances; persuasive but not binding in ordinary negligence, and often central in defining the professional standard of care.

Worked Example 1.6

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 and was tracked onto the lobby floor, making it slippery. The guest sues for negligence. Is the hotel’s compliance with custom a defense?

Answer:
No. Compliance with custom is admissible evidence suggesting the hotel acted as others do, but if the jury concludes that the customary practice of using undiluted chemical is itself unreasonably dangerous, the hotel may still be found negligent. Custom does not immunize a defendant if the custom is unsafe.

Worked Example 1.7

In a particular port, tugboat operators customarily do not carry radios, even though radios are inexpensive and would allow them to receive weather warnings. A tugboat owner follows this custom; a sudden storm that was announced over radio sinks the tug and its barge. The barge owner sues the tugboat owner for negligence. Does compliance with custom bar liability?

Answer:
No. The fact that no tugs in the port carry radios is evidence, but the jury may determine that a reasonable tug operator would use inexpensive, widely available safety technology. If so, the industry custom is itself negligent. The tug owner’s adherence to an unreasonable custom does not preclude a finding of breach.

Worked Example 1.8

An orthopedic surgeon performs a surgical procedure using a technique that is consistent with the methods taught and used by most orthopedic surgeons nationwide. The patient suffers an uncommon but known complication of the procedure and sues for malpractice, arguing the surgeon should have used a newer, more experimental technique with slightly lower complication rates. How does custom affect the analysis?

Answer:
In professional malpractice, the standard of care is usually defined by professional custom: what competent orthopedic surgeons ordinarily do. If the surgeon used the widely accepted technique and applied it with reasonable skill, she likely met the professional standard of care, even if some innovators use a different method. Custom is much more controlling here than in ordinary negligence.

Custom vs. Statutes

Sometimes both a statute and a custom address similar conduct:

• Statute plus custom: If a statute sets a minimum standard (e.g., guardrails of a certain height) and customary practice goes beyond it, a reasonable actor might need to follow both the statute and the higher custom if circumstances justify it.
• Custom without statute: If there is no statute, custom can be powerful evidence of what reasonable care demands.
• Statute contrary to custom: The statute controls. Custom cannot override a statutory standard of care.

Revision Tip

When analyzing a fact pattern:

• Ask first: Is there a statute or regulation that could trigger negligence per se?
• If yes, run through the four elements (clear standard, class of persons, type of harm, no excuse).
• Then ask: Is there any evidence of custom? Use it as persuasive evidence of breach or non-breach, remembering that:
  • Statutes can create automatic breach (if all elements are met).
  • Custom is never automatically controlling in ordinary negligence cases.

Summary

• Statutes and regulations can supply a statutory standard of care. If the defendant unreasonably violates such a statute and all negligence per se requirements are met, breach is established as a matter of law.
• Negligence per se requires:
  • A clear, specific standard of conduct.
  • A plaintiff within the statute’s protected class.
  • A harm of the type the statute was designed to prevent.
  • An unexcused violation that actually and proximately caused the harm.
• Even with negligence per se, the plaintiff must still prove causation and damages.
• A statutory violation may be excused when compliance was impossible, would have created greater danger, or was unreasonable in an emergency, among other recognized excuses.
• Compliance with a statute is not conclusive proof of reasonable care; circumstances may require additional precautions.
• A plaintiff’s own statutory violation can constitute contributory or comparative negligence per se, potentially limiting or barring recovery.
• Custom and industry practice are admissible but not conclusive evidence of what is reasonable conduct.
• In professional malpractice cases, professional custom usually defines the standard of care.
• Custom cannot override a statutory standard; where they conflict, the statute governs.

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 statutory or regulatory standard,
  • A plaintiff in the protected class,
  • Harm of the type the statute was meant to prevent,
  • An unexcused violation that causes the harm.
• If negligence per se does not apply, the statute may still be evidence of negligence.
• Recognized excuses (impossibility, greater danger, emergency, lack of knowledge of triggering facts) can prevent a statutory violation from being treated as negligence per se.
• Compliance with a statute is evidence of reasonable care but does not guarantee that the defendant was not negligent.
• A plaintiff’s violation of a safety statute can count as contributory or comparative negligence per se.
• Custom and industry practice are admissible to show what is ordinarily done, but they do not conclusively determine breach in ordinary negligence cases.
• In professional malpractice, custom is often controlling and effectively sets the standard of care.
• Statutes trump conflicting customs; custom cannot legalize conduct that violates a statutory safety rule.

Key Terms and Concepts

• Negligence Per Se
• Statutory Standard of Care
• Excused Violation
• Custom (in Negligence)
• Industry Custom
• Class of Persons
• Type of Harm