Negligence - Problems relating to proof of fault

Learning Outcomes

This article examines how core evidentiary and standard-of-care doctrines help prove breach of duty in negligence actions on the MBE, including:

• Using res ipsa loquitur to convert an unexplained accident into circumstantial proof of breach, identifying when the elements are satisfied, when “exclusive control” is flexible, and when alternative non-negligent explanations defeat the doctrine on exam fact patterns.
• Applying negligence per se where a criminal statute, ordinance, or regulation supplies a specific standard of conduct, recognizing protected classes and protected risks, and spotting facts that create valid excuses or limit the doctrine to mere evidence of negligence.
• Evaluating custom and usage evidence as it relates to the reasonable-person standard, distinguishing nonprofessional customs from professional or medical standards of care, and understanding when compliance or noncompliance with custom is powerful but not dispositive on the MBE.
• Distinguishing the different procedural effects of these doctrines—permissible inference, rebuttable presumption, or conclusive proof of duty and breach—so you can predict whether a case survives a motion for directed verdict or JMOL in multiple-choice questions.
• Comparing and contrasting res ipsa, negligence per se, and custom-based standards in mixed fact patterns, identifying which doctrine is most helpful to the plaintiff, and avoiding common distractors that misstate their elements or procedural consequences.
• Strengthening exam technique by translating doctrinal rules into quick issue-spotting checklists, enabling efficient elimination of wrong answer choices and precise selection of the doctrine that best addresses proof-of-fault problems.

MBE Syllabus

For the MBE, you are required to understand how breach of duty is established in negligence cases, particularly when direct evidence is lacking, with a focus on the following syllabus points:

• Define and apply the elements of Res Ipsa Loquitur
• Analyze the requirements for establishing Negligence Per Se through statutory violation
• Evaluate the role of custom and usage in determining the standard of care and breach
• Distinguish between the procedural effects of these doctrines

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. The doctrine of Res Ipsa Loquitur allows a plaintiff to establish an inference of negligence based on:
   1. Direct testimony from an eyewitness.
   2. The violation of a safety statute by the defendant.
   3. The fact that the accident is of a type that ordinarily does not occur absent negligence.
   4. Proof of industry custom establishing the standard of care.
2. For Negligence Per Se to apply based on the violation of a statute, the plaintiff must demonstrate that:
   1. The defendant acted with specific intent to violate the statute.
   2. The statute provides for a civil remedy for its violation.
   3. The plaintiff is within the class of persons the statute was intended to protect and suffered harm the statute was designed to prevent.
   4. The defendant’s violation was the sole cause of the plaintiff’s injury.
3. Evidence of custom or usage in a particular industry is generally:
   1. Conclusive proof of the standard of care.
   2. Irrelevant in determining whether the defendant breached a duty.
   3. Admissible as evidence of the standard of care, but not conclusive.
   4. Admissible only if the defendant was aware of the custom.

Introduction

Establishing the element of breach of duty is central to any negligence claim. On the MBE, breach is often the contested element, and examiners frequently present fact patterns where direct evidence of the defendant’s conduct is thin or ambiguous.

In such cases, plaintiffs may rely on structured doctrines that allow them to:

• Use circumstantial evidence to get past a motion for directed verdict / judgment as a matter of law (JMOL)
• Treat a statutory standard as the applicable standard of care
• Use evidence of how others behave (custom) to show what a reasonable person would do

This article focuses on three key methods used to address problems in proving fault:

• Res Ipsa Loquitur (the thing speaks for itself)
• Negligence Per Se (violation of statute or safety regulation)
• Custom and Usage (industry or professional practice)

These doctrines do not create new causes of action; they are evidentiary and standard-of-care tools that help establish breach.

Key Term: Res Ipsa Loquitur
A doctrine of evidence in tort law that permits an inference or presumption that a defendant was negligent in an accident injuring the plaintiff on the grounds that the accident was of a kind that does not usually happen without negligence.

Key Term: Inference
A logical conclusion drawn from proven facts. In res ipsa loquitur, negligence is inferred from the circumstances surrounding the accident, even without proof of a specific negligent act.

Key Term: Presumption
A rule that requires the fact-finder to assume a fact is true once another fact is established, unless the opposing party produces evidence to rebut it. Some jurisdictions treat res ipsa or statutory violations as creating presumptions of negligence.

Understanding when each doctrine applies, and what it does procedurally, is critical for eliminating wrong answer choices on the MBE.

Res Ipsa Loquitur

Res Ipsa Loquitur, Latin for "the thing speaks for itself," allows a plaintiff to reach the jury (and avoid a directed verdict / JMOL for the defendant) even when the plaintiff cannot identify the specific negligent act.

In res ipsa cases, the accident itself—combined with the surrounding circumstances—is used as circumstantial evidence that someone must have been careless, and that the defendant is the most likely careless party.

Common res ipsa fact patterns on the MBE include:

• Surgical instruments left inside a patient
• Barrels or objects falling from a warehouse or building
• Single-vehicle train or bus accidents where the vehicle leaves the tracks or road
• Elevator free-falls or sudden drops

Res Ipsa Loquitur Elements

To invoke Res Ipsa Loquitur, the plaintiff typically must establish:

1. The accident is of a kind that ordinarily does not occur in the absence of negligence The event must be unusual in a way that common experience says “this does not happen unless someone was careless.” The plaintiff need not identify the precise act of negligence—only that some negligence is the most probable explanation.

   • A sponge left in a patient’s abdomen
   • A train derailing on a clear day with normal track conditions
   • A chair collapsing under normal use shortly after purchase

   By contrast, accidents that frequently occur without negligence (e.g., a patient suffering a known non-negligent complication of surgery, a pedestrian tripping over their own shoelaces) generally do not support res ipsa.

2. The negligence is probably attributable to the defendant Traditionally, this is expressed as a requirement that the instrumentality or agent causing the harm was within the defendant’s exclusive control. Modern courts and the MBE focus less on literal exclusivity and more on whether:

   • The defendant was in a better position than the plaintiff to prevent or explain the accident, and
   • It is more likely than not that any negligence was the defendant’s negligence rather than that of some third party.

   Exclusive control is therefore flexible, especially where:

   • Multiple defendants jointly controlled the instrumentality (e.g., surgeon and hospital staff in an operating room)
   • The defendant had non-physical control (e.g., manufacturer over design and assembly of a product)

3. The injury was not due to the plaintiff’s own voluntary conduct Res ipsa traditionally required that the plaintiff’s own conduct did not contribute to the accident. In modern comparative fault jurisdictions, the focus is narrower: the doctrine is available so long as the plaintiff’s conduct does not provide an equally likely non-negligent explanation for the accident.

   • A patient unconscious during surgery clearly did not contribute to a sponge being left in her body.
   • A passenger seated on a bus has not caused the bus to roll over.

   Contributory or comparative negligence may still reduce recovery, but it does not generally bar the use of res ipsa.

Key Term: Industry Custom
The usual and regular way of doing things in a defined industry or trade. Compliance or noncompliance with industry custom may be relevant to breach but is generally not conclusive.

Note the distinction: res ipsa looks at how the accident happened, not at whether the defendant followed custom.

When Res Ipsa Loquitur Applies (and When It Does Not)

Res ipsa is appropriate where:

• The plaintiff lacks detailed information about the defendant’s internal operations
• The defendant is in a much better position to explain what went wrong
• The accident is strongly suggestive of negligence

Res ipsa is not appropriate where:

• There is direct, specific evidence of exactly what the defendant did wrong (you do not need the doctrine)
• The evidence shows multiple plausible non-negligent causes, none clearly less likely than negligence
• The plaintiff’s theory is purely speculative

On the MBE, watch for distractors saying res ipsa applies whenever the plaintiff lacks direct evidence. That is too broad. The doctrine is limited to a subset of such situations, where the accident itself strongly points toward negligence.

Res Ipsa Loquitur and Multiple Defendants

Some jurisdictions and exam questions involve res ipsa against multiple defendants (often in medical cases where several parties had joint control of the instrumentalities).

• The requirement of “exclusive control” can be satisfied if the defendants, collectively, had control.
• If res ipsa is used against multiple defendants who cannot identify the responsible party, they may be held jointly and severally liable, subject to contribution claims among themselves.

This fits with general MBE rules that allow joint and several liability where multiple parties may be responsible for a single, indivisible injury.

Res Ipsa Loquitur Procedural Effect

The primary procedural effect of successfully invoking res ipsa is to defeat a motion for directed verdict / JMOL by the defendant. It allows the case to reach the jury based on circumstantial evidence.

• Majority View: Res ipsa creates a permissible inference of negligence.

  • The jury may infer negligence but is not required to, even if the defendant offers no explanation.
  • The burden of production stays with the plaintiff; the burden of persuasion on negligence always remains with the plaintiff.

• Minority Views:

  • Some jurisdictions treat res ipsa as creating a rebuttable presumption of negligence, shifting the burden of production to the defendant to offer some non-negligent explanation.
  • A few treat it as shifting the burden of persuasion on negligence to the defendant.

On the MBE, unless told otherwise, assume the inference approach.

Key Term: Burden of Production
The obligation to come forward with enough evidence on an issue to avoid having the issue taken away from the jury.

Key Term: Burden of Persuasion
The obligation to convince the fact-finder to a particular standard (e.g., preponderance of the evidence) that a fact is true.

Worked Example 1.1

Patient underwent abdominal surgery performed by Surgeon at Hospital. Following the surgery, Patient experienced severe pain. X-rays revealed a surgical sponge left inside Patient's abdomen. Patient sues Surgeon and Hospital. Direct evidence of who left the sponge is unavailable as several staff members were present. Can Patient utilize Res Ipsa Loquitur?

Answer:
Yes, likely.

• The accident (retained sponge) ordinarily does not occur without negligence.
• The instrumentalities (sponge and surgical field) were under the control of Surgeon and Hospital staff, who collectively had exclusive control during the operation.
• Patient was unconscious and did not contribute to the injury.

Res ipsa allows an inference of negligence against Surgeon and Hospital so the case can go to the jury. Some jurisdictions would treat this as a presumption, shifting the burden of producing evidence to the defendants.

Worked Example 1.2

A passenger is injured when a bus leaves a straight, dry highway in clear weather and rolls over. There is no direct evidence of why the bus left the road. The passenger sues the bus company. Does res ipsa loquitur apply?

Answer:
Likely yes.

• Buses do not ordinarily leave straight, dry highways in clear weather absent negligence (driver carelessness, improper maintenance, etc.).
• The bus was under the company’s control (through its driver and maintenance personnel).
• The passenger, seated and not distracting the driver, did not contribute to the accident.

Res ipsa permits the jury to infer negligence by the bus company, defeating a motion for directed verdict / JMOL.

Violation of Statute (Negligence Per Se)

Negligence Per Se allows a plaintiff to satisfy the duty and breach elements of negligence by showing that the defendant violated a statute or safety regulation designed to protect against the type of accident that occurred.

Key Term: Negligence Per Se
A doctrine under which an unexcused violation of a qualifying statute or regulation is treated as conclusive (or at least prima facie) proof of duty and breach, leaving causation and damages to be proved separately.

Key Term: Statutory Standard of Care
The specific conduct required by a statute or regulation; when negligence per se applies, this statutory standard replaces the general reasonable-person standard.

Elements

For a statute's violation to constitute Negligence Per Se, the following conditions must generally be met:

1. The statute provides a criminal penalty The statute must impose a specific duty for the protection of others, generally evidenced by criminal enforcement (fine, imprisonment, or both). This includes:

   • State criminal statutes
   • Municipal ordinances
   • Administrative regulations with penal sanctions

   A statute that is purely revenue-raising (e.g., a licensing fee with no safety purpose) may not qualify.

2. The standard of conduct is clearly defined The statute must prescribe specific, definite conduct (“must have headlights on,” “must fence pools with a six-foot barrier”) rather than vague admonitions.

3. The plaintiff is in the class of persons the statute was designed to protect The legislature must have had plaintiffs like this one in mind when enacting the statute.

   • A child injured by a violation of a child safety statute is within the protected class.
   • A burglar injured while violating a burglary statute is not within the class the burglary statute aims to protect.

4. The harm is of the type the statute was intended to prevent The injury must be the kind of harm that the statute was meant to guard against.

   • A pool-fencing ordinance is aimed at preventing drownings or pool-related injuries, not at preventing neighbor disputes over aesthetics.
   • A statute requiring headlights is aimed at preventing nighttime collisions, not at preventing theft of headlight bulbs.

Key Term: Protected Class
The group of persons the legislature intended to protect by enacting the statute or regulation.

Key Term: Type of Risk
The category of harm (e.g., car collisions, drownings, fires) the statute was designed to prevent.

If any of these elements is missing, negligence per se does not apply, though the statutory violation may still be admissible as some evidence of negligence.

Excuses for Violation

Even when the statute qualifies, a defendant may avoid negligence per se by showing that the violation was reasonable or excused under the circumstances. Common excuses include:

• Compliance was more dangerous than violation

  • Swerving over the center line to avoid hitting a child.

• Compliance was impossible or beyond defendant’s control

  • A driver suffers a sudden, unforeseeable heart attack and drifts across a center line.

• Emergency not due to defendant’s own making

  • Sudden brake failure despite proper maintenance.

• Incapacity

  • Young children or physically disabled persons may be excused if they exercised the care reasonable for someone of their age or condition.

• Reasonable care in attempting to comply

  • A driver who reasonably checks lights and brakes but a bulb blows out moments before the accident.

• Statute is vague or confusing

  • The defendant reasonably interpreted an ambiguous provision.

Key Term: Excused Violation
A statutory violation that, due to specific circumstances, does not result in negligence per se, although it may still be some evidence of negligence.

On the MBE, look for facts explicitly showing that compliance was impossible, riskier, or that the defendant acted reasonably in trying to obey the statute.

Procedural Effect

• Majority View: An unexcused violation of a qualifying statute constitutes negligence per se—a conclusive presumption of duty and breach. The plaintiff must still prove factual and proximate causation and damages.

• Minority Views: Some jurisdictions treat the violation as only:

  • Prima facie evidence of negligence (the jury may still find no breach), or
  • A rebuttable presumption that can be overcome by evidence showing reasonable conduct under the circumstances.

Compliance with a statute does not automatically establish due care. It sets a floor, not a ceiling. A reasonable person might be required to do more than the statutory minimum if the circumstances demand it (e.g., driving below the speed limit in icy conditions).

Key Term: Statutory Standard of Care
The minimum level of conduct required by a statute; a defendant may be negligent for failing to do more than this minimum when reasonable under the circumstances.

Plaintiff’s Statutory Violations

The negligence per se doctrine also applies to plaintiffs:

• In contributory negligence jurisdictions, a plaintiff’s unexcused violation of a safety statute may bar recovery.
• In comparative fault jurisdictions, such a violation will typically be treated as negligence and reduce the plaintiff’s recovery proportionally.

Licensing Statutes

Not every statutory violation gives rise to negligence per se. Courts distinguish:

• Safety-oriented licensing statutes (e.g., licensing of drivers, doctors, electricians): violation may support negligence per se if the statute’s purpose is to protect the public from unqualified practitioners.
• Revenue-raising licensing statutes (e.g., business license fees with no safety purpose): violation usually does not support negligence per se, though it may be relevant to other issues (e.g., contract enforceability).

On the MBE, look for explicit language indicating the statute’s purpose.

Key Term: Professional Standard of Care
The level of skill and knowledge ordinarily possessed and exercised by members of a profession in good standing. For professionals, this standard is often derived from custom and sometimes enforced through statutory or regulatory schemes.

Worked Example 1.3

A city ordinance requires all fences around swimming pools to be at least six feet high. Homeowner built a four-foot fence around his pool. Child, age 5, climbed over the fence, fell into the pool, and suffered injuries. Child's parents sue Homeowner. Does the violation of the ordinance establish negligence per se?

Answer:
Yes, likely.

• The ordinance imposes a specific duty (six-foot fence) and is safety-oriented.
• Children who may wander near pools are within the protected class.
• Drowning or pool-related injuries are exactly the type of harm the ordinance aims to prevent.
• The injury resulted from the failure to have a compliant fence, and no excuse is suggested.

Homeowner’s unexcused violation constitutes negligence per se (duty and breach). Plaintiffs still must prove causation and damages.

Worked Example 1.4

A statute makes it a misdemeanor to drive without a valid driver’s license. Driver, whose license expired last week, is involved in a collision with Pedestrian when Pedestrian jaywalks into traffic. Pedestrian sues Driver, arguing that Driver is negligent per se for driving without a license. Does negligence per se apply?

Answer:
Likely no.

• Even if the licensing statute is safety-oriented, Pedestrian’s injury must be of the type the statute was designed to prevent. Courts are divided here, but many treat “no license” statutes as aimed primarily at administrative regulation rather than as defining the standard for safe driving in a given accident.
• More importantly, Pedestrian cannot show causation between Driver’s lack of a license and the specific collision. The crash likely resulted from Pedestrian’s jaywalking, not from anything about Driver’s licensure status.

Thus, Driver’s lack of a license is not negligence per se on these facts, though it might be admissible as some evidence of negligence in some jurisdictions.

Custom and Usage

Evidence of custom or usage within a particular industry, trade, or community may be relevant to establishing the standard of care in a negligence case.

Key Term: Custom
A well-established, regular, and widely observed practice in a particular trade, industry, profession, or community.

Key Term: Professional Standard of Care
The level of care, skill, and learning ordinarily possessed and exercised by members of a profession in good standing under similar circumstances. For many professionals, this standard is heavily informed by professional custom.

Admissibility and Effect

• General Rule (Nonprofessionals):
  Evidence of custom is admissible to show what the community or industry typically does, but it is not conclusive:

  • Failure to follow custom is evidence of negligence, but does not compel a finding of negligence.
  • Compliance with custom is evidence of due care, but does not compel a finding of due care if a reasonable person would have done more.

  Courts and the MBE are clear: “Everyone does it” is not a complete defense if the custom itself is careless.

• Professional Standard of Care:
  For professionals (doctors, lawyers, accountants, architects, engineers, etc.), custom often is the standard of care:

  • Departure from customary professional practice is usually strong evidence of breach.
  • Compliance with professional custom is strong evidence of due care, though in rare cases a custom may itself be found unreasonable.

  In medical malpractice:

  • Historically, many jurisdictions used a “same or similar locality” rule (compare the defendant to other physicians in the same or similar community).
  • The modern trend is toward a national standard for specialists and widely available procedures.
  • Informed consent duties are also typically defined by professional custom, sometimes modified by statute.

Key Term: Industry Custom
The standard practices of an industry. It may raise or lower the baseline of reasonable care but is ultimately subordinate to the reasonable-person standard.

Custom vs Habit

Do not confuse custom with habit:

• Custom: General practice of a broad group (e.g., “Most tugboat owners do not carry radios”).
• Habit: Semi-automatic, regular response by a specific individual or entity (e.g., “This driver always checks his blind spot before changing lanes”).

Habit evidence is governed by rules of evidence and, unlike general custom, may be admissible to show that the actor likely behaved in the same way on the occasion in question.

Custom and Safety Regulations

Custom can interact with statutes and regulations:

• A statutory or regulatory minimum often sets a floor, not the whole standard of care.
• Custom may exceed the statutory minimum (e.g., most businesses go beyond code requirements), in which case failure to follow custom may be evidence that more precaution was reasonably required.
• Custom that falls below statutory requirements is irrelevant because the statute controls.

Worked Example 1.5

A tugboat operating in coastal waters does not carry a working radio, even though most tugboats in the area routinely do so. During a sudden storm, the tugboat is unable to receive weather warnings and sinks. The owner sues the tugboat company for negligence. The company argues that there was no statute requiring radios. Is evidence of industry custom relevant?

Answer:
Yes.

Evidence that other tugboat companies customarily carry radios is admissible as evidence of the standard of care. The jury may conclude that a reasonably prudent tugboat operator would follow that custom, even though no statute required radios.

The company’s failure to follow custom is not automatically negligence, but it is strong evidence that the company breached its duty of reasonable care.

Exam Warning

Do not confuse the non-conclusive nature of general custom with the more dispositive role of professional custom:

• For nonprofessionals, the jury still determines whether the defendant acted reasonably under all the circumstances, even if the defendant complied with custom.
• For professionals, the custom usually defines reasonableness, and expert testimony about custom is often essential.

On the MBE, be wary of answer choices that state:

• “Because the defendant complied with industry custom, he could not be negligent.” (Too strong)
• “Evidence of custom is inadmissible because it invades the province of the jury.” (Incorrect; it is generally admissible but not conclusive.)

Key Point Checklist

This article has covered the following key knowledge points:

• Res Ipsa Loquitur applies when the type of accident ordinarily does not occur without negligence, the instrumentality was probably in the defendant’s control, and the plaintiff did not contribute in a way that provides an alternative non-negligent explanation.
• The main procedural effect of Res Ipsa Loquitur is to defeat a directed verdict / JMOL and allow the jury to infer negligence; in most jurisdictions it creates a permissible inference, not a mandatory presumption.
• Negligence Per Se uses an unexcused violation of a qualifying statute to establish duty and breach when the plaintiff is within the protected class and suffers the type of harm the statute was designed to prevent.
• Unexcused statutory violations generally constitute negligence per se (conclusive duty and breach) in most jurisdictions, but some treat them as only prima facie evidence or rebuttable presumptions of negligence.
• Excused statutory violations (e.g., compliance impossible, compliance more dangerous, sudden emergencies) prevent negligence per se, though the violation may still be some evidence of negligence.
• Custom and usage evidence is admissible to show the standard of care but is generally not dispositive, except that professional custom often defines the standard of care in malpractice cases.
• Compliance with custom or statute sets a minimum standard of care but does not guarantee that the defendant acted reasonably if ordinary prudence required additional precautions.

Key Terms and Concepts

• Res Ipsa Loquitur
• Inference
• Presumption
• Burden of Production
• Burden of Persuasion
• Negligence Per Se
• Statutory Standard of Care
• Protected Class
• Type of Risk
• Excused Violation
• Custom
• Industry Custom
• Professional Standard of Care