California Bar Negligence Breach
Last updated: May 2, 2026
Negligence Breach questions are one of the highest-leverage areas to study for the California Bar. This guide breaks down the rule, the elements you need to recognize, the named traps that catch most students, and a memory aid that scales to test day. Read it once, then practice the same sub-topic adaptively in the app.
The rule
Breach is the second element of negligence: the plaintiff must prove the defendant's conduct fell below the applicable standard of care. The default standard is the reasonably prudent person under the circumstances (Restatement (Third) of Torts: Liab. for Phys. & Emot. Harm §3). Breach is typically proved either (1) directly, by showing what the defendant did and arguing it was unreasonable (often using the Hand formula B < P×L), (2) by negligence per se where the defendant violated a safety statute designed to protect a class to which plaintiff belongs against the type of harm suffered, or (3) by res ipsa loquitur, an inferential method allowing the jury to infer breach from the nature of the accident. California follows the same general framework (CACI 401), but applies its own version of negligence per se as a rebuttable presumption under Cal. Evid. Code §669.
Elements breakdown
Reasonable Person Standard (Default)
Conduct is judged against what a reasonably prudent person would have done under the same or similar circumstances.
- Objective standard, not defendant's subjective best effort
- Same or similar external circumstances considered
- Physical disabilities incorporated into standard
- Mental disabilities and voluntary intoxication NOT incorporated
- Defendant's superior skill or knowledge held against them
Professional Standard of Care
A professional must exercise the knowledge, skill, and care ordinarily possessed and used by members of the profession in good standing.
- Defendant holds out as having professional skill
- Conduct measured against custom of profession
- National standard for board-certified specialists (majority)
- Expert testimony required to establish standard
- Departure from professional custom causing harm
Child Standard of Care
A child is held to the standard of a reasonable child of similar age, intelligence, and experience — unless engaged in an adult or inherently dangerous activity.
- Child of like age, intelligence, and experience
- Subjective elements blended with objective measure
- Adult standard applies for adult activities
- Adult standard applies for inherently dangerous activities
- Generally inapplicable to children under 4-5
Negligence Per Se
Violation of a statute, ordinance, or regulation establishes breach as a matter of law (or as a rebuttable presumption in California) when statutory conditions are met.
- Defendant violated a safety statute or regulation
- Plaintiff is in the class statute aims to protect
- Harm is the type the statute aims to prevent
- Violation was the actual and proximate cause
- No recognized excuse for the violation (emergency, incapacity, compliance impossible)
Res Ipsa Loquitur
The plaintiff may invoke an inference of breach where the accident is one that ordinarily does not occur absent negligence and the instrumentality was within the defendant's control.
- Accident type ordinarily does not occur without negligence
- Instrumentality was in defendant's exclusive control
- Plaintiff did not contribute to the harm
- Evidence of cause more accessible to defendant
- Effect: jury may (not must) infer breach
Hand Formula (B < P×L)
A widely-cited analytical tool: conduct is unreasonable when the burden of avoiding harm is less than the probability of harm multiplied by its likely magnitude.
- B = burden of taking the precaution
- P = probability the harm would occur
- L = magnitude of the loss if it occurred
- Breach exists where B < P×L
- Used as argumentation tool, not strict formula
Custom Evidence
Evidence of industry custom is admissible and probative of the standard of care, but is not dispositive — an entire industry can be negligent.
- Custom is relevant but not conclusive
- Compliance with custom is shield, not absolute defense
- Departure from custom is sword, not automatic breach
- Jury weighs custom against reasonableness inquiry
- Different rule for professional malpractice (custom controls)
Common patterns and traps
The Custom-Compliance Shield Trap
A distractor states that the defendant cannot be liable because its conduct conformed to industry custom. In ordinary negligence (non-professional), this is wrong: T.J. Hooper (and the Restatement) hold that an entire industry can be unreasonably lax. Custom is evidence the jury weighs, not a safe harbor. The trap inverts the rule by treating custom as dispositive.
Looks like: 'No, because the warehouse followed standard industry practice for stacking pallets.' Sounds protective but ignores that the practice itself may be unreasonable.
The Negligence Per Se Class-Mismatch Trap
A choice invokes negligence per se whenever a statute is violated, ignoring the requirement that plaintiff be in the protected class and the harm be the type the statute aims to prevent. Examiners draft statutes that look general but were enacted for a different purpose (e.g., a licensing statute aimed at revenue, not safety). The trap rewards mechanical statute-spotting without the matching analysis.
Looks like: 'Yes, because Reyes violated the vehicle code section requiring annual inspections.' Wrong if the inspection statute aims at emissions, not collision safety.
The Res Ipsa as Strict Liability Trap
Choices treat res ipsa loquitur as conclusively establishing breach or as shifting the burden of proof to the defendant. In most jurisdictions and on the MBE, res ipsa creates only a permissible inference — the jury may, but need not, find breach. Confusing inference with presumption is a classic distractor pattern.
Looks like: 'Yes, because res ipsa loquitur establishes negligence as a matter of law where an instrument under defendant's control causes injury.' Overstates the doctrine's effect.
The California Negligence Per Se Switch
On a California-flavored question, distractors apply the majority rule that statutory violation conclusively establishes breach. California treats negligence per se as a rebuttable presumption under Evid. Code §669, which the defendant can rebut by showing they did what a reasonable person would have done under the circumstances. Watch for facts placing the case in California state court.
Looks like: 'Yes, because under California law, violation of a safety statute conclusively establishes breach.' Wrong because the presumption is rebuttable.
The Subjective Best-Effort Trap
A distractor excuses the defendant because they tried their best, were inexperienced, or had a momentary lapse. The reasonable person standard is objective; good-faith effort is irrelevant. The trap appeals to fairness intuition over doctrine.
Looks like: 'No, because the new driver was doing the best she could given her inexperience.' The standard is the reasonable driver, not the reasonable inexperienced driver.
How it works
On the bar, breach is rarely the issue you spot first — duty and causation tend to dominate the call — but it is where examiners hide their best traps. You start by identifying the standard of care that applies (default reasonable person, or one of the calibrated standards for professionals, children, or common carriers). Then you ask how breach is being proved. If a statute is on the page, run the negligence per se checklist: protected class, type of harm, causation, and excuse. If the facts are mysterious — a barrel falls from a warehouse window, a sponge is left inside a patient — think res ipsa. For a plain reasonableness theory, marshal the Hand-formula factors: how cheap was the precaution, how likely was the harm, how bad would it have been? Imagine Reyes, a delivery driver, who runs a stop sign painted by the city as a safety measure on a residential street, striking a pedestrian — negligence per se locks in breach without a jury debate over reasonableness, and the analysis ends quickly.
Worked examples
How should the court rule on Liu's motion for a directed verdict?
- A Grant the motion, because uniform industry custom conclusively establishes the standard of care.
- B Grant the motion, because Patel was not Liu's employee and Liu owed him no duty regarding stacking practices.
- C Deny the motion, because a jury could find that the industry's customary practice was itself unreasonable. ✓ Correct
- D Deny the motion, because res ipsa loquitur conclusively establishes Liu's breach as a matter of law.
Why C is correct: Industry custom is admissible evidence of the standard of care but is not dispositive in ordinary negligence cases — an entire industry can be unreasonably lax (T.J. Hooper; Restatement (Third) §13). With expert testimony that cheap bracing would have prevented the collapse, a reasonable jury could apply the Hand formula and find that B was less than P×L. The motion for directed verdict must therefore be denied.
Why each wrong choice fails:
- A: This invokes the Custom-Compliance Shield Trap. Custom is evidence the jury weighs, not a conclusive shield in ordinary (non-professional) negligence. The rule would be different in a medical malpractice case, but stacking pallets is not a learned profession. (The Custom-Compliance Shield Trap)
- B: Wrong element. Liu owes a duty of reasonable care to invitees on its premises, including delivery drivers like Patel; this is a classic business-invitee scenario. The motion must be analyzed on breach, not duty.
- D: Overstates res ipsa, which creates only a permissible inference, not a conclusive presumption. Even if the doctrine applied, it would defeat — not support — a directed verdict for Liu, but it does not establish breach 'as a matter of law.' (The Res Ipsa as Strict Liability Trap)
What is the most likely effect of the headlight statute on the breach analysis?
- A Reyes's violation conclusively establishes breach because the statute was designed to protect pedestrians from nighttime collisions.
- B The statute is irrelevant to the breach analysis because Reyes did not intentionally violate it.
- C The violation creates a rebuttable presumption of breach that Reyes may overcome by showing she acted as a reasonable person under the circumstances. ✓ Correct
- D Negligence per se does not apply because Okafor must first prove breach under the ordinary reasonable-person standard before invoking the statute.
Why C is correct: This is a California state-court case, so California Evidence Code §669 governs: violation of a safety statute creates a rebuttable presumption of negligence. Reyes can rebut by showing she did what a reasonable person would have done — here, the sudden, undetectable headlight failure thirty minutes into her drive is exactly the kind of excuse that defeats the presumption. The protected-class and type-of-harm prongs are clearly met (pedestrian; collision), so the statute applies, but rebuttably.
Why each wrong choice fails:
- A: This is the California Negligence Per Se Switch trap — applies the majority rule (conclusive breach) instead of California's rebuttable-presumption framework under Evid. Code §669. (The California Negligence Per Se Switch)
- B: Negligence per se does not require intent to violate the statute; it requires only that the defendant's conduct violated it. Strict reading of the doctrine — intent is irrelevant.
- D: Inverts the doctrine. Negligence per se substitutes statutory breach for the ordinary reasonable-person showing — it does not require a separate breach finding as a precondition.
Which doctrine most directly supports Patel's prima facie case on breach?
- A Negligence per se, because retaining a sponge inside a patient violates the hospital's written sponge-count protocol.
- B Res ipsa loquitur, because the harm is of a type that ordinarily does not occur absent negligence and the surgical team had exclusive control. ✓ Correct
- C The professional malpractice standard, requiring expert testimony establishing the specific deviation from the medical standard of care.
- D Strict liability, because surgery is an inherently dangerous activity for which the surgeon is liable without regard to fault.
Why B is correct: Res ipsa is tailor-made for the retained-surgical-sponge scenario: the accident does not ordinarily occur without negligence, the instrumentality (the sponge and the closure) was within the surgical team's exclusive control, and the anesthetized plaintiff plainly did not contribute to it. Res ipsa lets Patel reach the jury without identifying which team member was negligent — the inference is permissible. Expert testimony that retained sponges essentially never happen absent negligence supplies the foundation for the first prong.
Why each wrong choice fails:
- A: A private hospital protocol is not a 'statute, ordinance, or regulation' and does not trigger negligence per se. Internal rules can be evidence of the standard of care but are not statutory violations. (The Negligence Per Se Class-Mismatch Trap)
- C: Ordinarily true in malpractice, but the retained-sponge scenario is the canonical exception: res ipsa permits the inference without specific expert testimony identifying the deviation, because laypersons can recognize that sponges do not belong inside patients.
- D: Surgery is not subject to strict liability — it is a professional service governed by the malpractice standard. Strict liability is reserved for abnormally dangerous activities and certain product liability claims, not medical procedures.
Memory aid
For breach analysis, run 'SCRP': Standard (which one applies?), Conduct (what did D do?), Reasonableness (Hand formula or custom?), Per se / Res ipsa (any shortcut available?). For negligence per se specifically: 'Class + Harm + Cause + No Excuse'.
Key distinction
The decisive line is between (a) custom evidence — relevant but never conclusive in ordinary negligence cases, and (b) professional custom — which IS the standard in malpractice. A wrong answer that says 'D wins because she followed industry custom' is almost always a trap in a non-professional case; that same answer is correct in a medical malpractice case.
Summary
Breach is fall-below-the-standard, and you prove it directly (Hand formula, custom evidence), categorically (negligence per se), or inferentially (res ipsa) — pick the right tool for the facts on the page.
Practice negligence breach adaptively
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Start your free 7-day trialFrequently asked questions
What is negligence breach on the California Bar?
Breach is the second element of negligence: the plaintiff must prove the defendant's conduct fell below the applicable standard of care. The default standard is the reasonably prudent person under the circumstances (Restatement (Third) of Torts: Liab. for Phys. & Emot. Harm §3). Breach is typically proved either (1) directly, by showing what the defendant did and arguing it was unreasonable (often using the Hand formula B < P×L), (2) by negligence per se where the defendant violated a safety statute designed to protect a class to which plaintiff belongs against the type of harm suffered, or (3) by res ipsa loquitur, an inferential method allowing the jury to infer breach from the nature of the accident. California follows the same general framework (CACI 401), but applies its own version of negligence per se as a rebuttable presumption under Cal. Evid. Code §669.
How do I practice negligence breach questions?
The fastest way to improve on negligence breach is targeted, adaptive practice — working questions that focus on your specific weak spots within this sub-topic, getting immediate feedback, and revisiting items you missed on a spaced-repetition schedule. Neureto's adaptive engine does this automatically across the California Bar; start a free 7-day trial to see your sub-topic mastery climb in real time.
What's the most important distinction to remember for negligence breach?
The decisive line is between (a) custom evidence — relevant but never conclusive in ordinary negligence cases, and (b) professional custom — which IS the standard in malpractice. A wrong answer that says 'D wins because she followed industry custom' is almost always a trap in a non-professional case; that same answer is correct in a medical malpractice case.
Is there a memory aid for negligence breach questions?
For breach analysis, run 'SCRP': Standard (which one applies?), Conduct (what did D do?), Reasonableness (Hand formula or custom?), Per se / Res ipsa (any shortcut available?). For negligence per se specifically: 'Class + Harm + Cause + No Excuse'.
What's a common trap on negligence breach questions?
Treating compliance with industry custom as automatic non-breach
What's a common trap on negligence breach questions?
Skipping the protected-class/type-of-harm prongs of negligence per se
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