34.2 Standard of Care, Custom, Negligence Per Se & Res Ipsa Loquitur

34.2 Standard of Care, Custom, Negligence Per Se & Res Ipsa Loquitur

Once a duty exists, the next questions are what standard of care applies and whether the defendant fell short of it. NCBE's outline covers the reasonably prudent person standard, special classes of defendants, custom, violation of statutes, and problems of proof such as res ipsa loquitur.

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The Standard of Care

The Basic Standard: The Reasonably Prudent Person (RPP)

The standard of care owed by an ordinary adult is that of a hypothetical Reasonably Prudent Person under like circumstances. This is an objective, external baseline that does not bend to personal idiosyncrasies, lower intelligence, or clumsy temperament.

• Physical Characteristics Factored In: The RPP standard incorporates the actor's physical handicaps or conditions. A blind person is held to the standard of a reasonably prudent blind person; a person suffering a sudden, unheralded stroke while driving is judged accordingly.
• Mental & Cognitive Characteristics Excluded: Mental illness, cognitive deficits, intellectual limitations, emotional instability, and insanity are not considered. A person suffering from a psychiatric delusion or dementia is held strictly to the objective standard of a sane, reasonably prudent adult.
• Voluntary Intoxication Excluded: An intoxicated person is held to the standard of a sober, reasonably prudent individual.
• Superior Skill or Knowledge Elevates Standard: If an actor possesses specialized training, knowledge, or superior skills (e.g., an experienced race car driver, a master structural engineer), the standard rises: the actor must exercise the standard of care expected of a reasonably prudent person possessing those identical superior skills.

Special Standards of Care

1. Children

• The Subjective-Objective Standard: A child is held to the standard of a reasonable child of like age, intelligence, and experience. This creates a tailored standard that accounts for child development.
• The Adult Activity Exception: If a minor engages in an activity that is inherently dangerous and normally reserved for adults—most notably operating a motorized vehicle (automobile, motorboat, motorcycle, snowmobile, airplane)—the child standard is discarded. The minor is held to the objective adult RPP standard.
• Rule of Sevens (Traditional Common Law): Children under 7 are conclusively presumed incapable of negligence; children 7–14 are rebuttably presumed incapable; children over 14 are rebuttably presumed capable. Most modern courts apply the age, intelligence, and experience standard instead, although the Restatement (Third) of Torts treats children under five as incapable of negligence.

2. Professionals

• The Customary Standard: A professional (physician, attorney, accountant, architect) must exercise the knowledge, skill, and care ordinarily possessed and exercised by average members of that profession in good standing.
• Custom Sets the Standard: Unlike ordinary negligence cases, in which an entire industry's custom can be found negligent, professional malpractice cases generally use the profession's customary practice as the standard of care. Courts only rarely find a whole profession's practice negligent, as in Helling v. Carey (Wash. 1974), which involved a routine glaucoma test.
• Geographic Scope: Most jurisdictions hold medical specialists to a national standard of care, while general practitioners are evaluated under a modified "similar locality" or national rule.
• Expert Testimony Required: A plaintiff must present expert testimony to establish the professional standard and its breach, unless the negligence is so conspicuous that it falls within the common knowledge of laypersons (e.g., leaving a surgical clamp inside a patient's abdomen, or operating on the wrong limb).
• Doctrine of Informed Consent: A physician must disclose the material risks of, and alternatives to, a proposed treatment. Many states ask what a reasonable patient would consider significant (Canterbury v. Spence, D.C. Cir. 1972); others ask what a reasonable physician would disclose. The plaintiff must also show that a reasonable patient, properly informed, would have declined the treatment and that the undisclosed risk caused the injury.

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Statutory Standards: Negligence Per Se

A criminal statute or safety ordinance replaces the general common law standard of care with a specific statutory mandate under the doctrine of Negligence Per Se.

The Two-Prong Test

Negligence per se applies if, and only if:

1. Class of Persons: The plaintiff belongs to the class of persons the statute was specifically designed to protect; AND
2. Type of Harm: The injury suffered is the type of hazard or harm the statute was enacted to prevent.

• Legal Consequence: In most states, an unexcused violation establishes duty and breach (negligence per se). Some states treat the violation as a rebuttable presumption of negligence or merely as evidence of negligence. The plaintiff must still prove causation and damages.
• Excuses for Statutory Violation: Compliance is excused, and no negligence per se attaches, if:
  1. Compliance would cause greater physical danger to life or property than violation (e.g., swerving across a double-yellow line into opposing lanes to avoid hitting a running toddler);
  2. Compliance was impossible due to sudden, unheralded physical incapacitation or external events beyond the defendant's control (e.g., sudden hydraulic brake line rupture in a brand-new car).

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Breach of Duty and Proof

Breach occurs when the defendant's conduct fails to conform to the applicable standard of care, exposing others to unreasonable risks.

The Learned Hand Formula (United States v. Carroll Towing Co.)

Judge Learned Hand framed breach as an algebraic calculation: liability attaches if the Burden (B) of taking adequate precautions is less than the Probability (P) of harm multiplied by the Gravity / Loss (L) of the resulting injury:

$\text{Breach exists if } B < P \times L$

If an inexpensive safety latch ($10) would prevent an explosion causing $1,000,000 in damage with a 1% probability ($10,000 expected loss), the burden is far less than the expected risk, and failing to install the latch constitutes a breach.

Res Ipsa Loquitur ("The Thing Speaks for Itself")

Res ipsa loquitur is a circumstantial evidentiary doctrine that permits a jury to infer negligence and breach in the absence of direct evidence.

• The Three Prima Facie Requirements:

  1. The event is of a kind that ordinarily does not occur in the absence of negligence;
  2. The instrumentality causing the injury was within the exclusive control of the defendant (many modern courts ask more broadly whether the negligence was probably the defendant's); and
  3. The injury was not due to any voluntary action or contribution by the plaintiff (comparative fault states often drop this requirement and reduce damages instead).

• Procedural Consequence:

  • Res ipsa loquitur establishes a permissible inference of negligence. It does not create a mandatory presumption and does not shift the burden of proof to the defendant.
  • Effect on Motions for Directed Verdict: Res ipsa loquitur allows the plaintiff's case to survive the defendant's motion for a directed verdict and reach the jury. If the plaintiff successfully establishes res ipsa loquitur, the defendant's motion for a directed verdict must be denied.

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More on the Standard of Care

Sudden Emergency

A person who faces a sudden emergency that she did not create is judged by what a reasonable person would do in the same emergency. Many comparative fault states no longer give a separate emergency instruction, treating the emergency as one of the circumstances under the ordinary reasonable-care standard.

Custom in Ordinary Negligence Cases

Evidence that a defendant followed, or departed from, the customary practice of its industry is admissible and relevant, but it is not conclusive. An entire industry may lag behind reasonable precautions. In The T.J. Hooper (2d Cir. 1932), tugboat owners were negligent for failing to equip their boats with radio receivers, even though most tugboats did not have them.

Negligence Per Se in More Detail

• Excuses: A violation may be excused if the actor's incapacity made compliance unreasonable, the actor neither knew nor should have known of the facts requiring compliance, the actor made a reasonable effort to comply, the actor faced an emergency not of its own making, or compliance would have created a greater risk.
• Licensing statutes: Violating a licensing statute, such as driving without a license, generally is not negligence per se, because the lack of a license does not show that the defendant's conduct was careless.
• Compliance: Complying with a statute or regulation is evidence of due care, but it does not conclusively establish that the defendant was not negligent; statutes usually set minimum standards.
• Regulations and ordinances: Most states treat violations of administrative regulations and local ordinances like violations of statutes, although some treat them only as evidence of negligence.

Proof of Breach: Additional Points

• Slip-and-fall cases: A plaintiff generally must show that the defendant created the dangerous condition or had actual or constructive notice of it, meaning it existed long enough that reasonable inspection would have discovered it. Some states relax this requirement for self-service stores when the store's method of operation makes such hazards foreseeable.
• Res ipsa loquitur against several defendants: In Ybarra v. Spangard (Cal. 1944), an unconscious surgical patient who suffered an unexplained shoulder injury was allowed to invoke res ipsa loquitur against the doctors and nurses who had control over him during the operation.
• Strength of the inference: In most states, res ipsa loquitur permits but does not require the jury to infer negligence. A few states give it the effect of a presumption that shifts to the defendant the burden of producing evidence.