California’s CACI negligence jury instructions, found in the 400 series of the Judicial Council of California Civil Jury Instructions, tell jurors exactly what a plaintiff must prove in a negligence case: that the defendant was negligent, that the plaintiff was harmed, and that the negligence was a substantial factor in causing that harm. The instructions also define the standard of care, explain causation when more than one cause is involved, set out shortcuts like negligence per se and res ipsa loquitur, and cover defenses such as comparative fault and assumption of risk. The underlying duty comes from Civil Code section 1714, which makes everyone responsible for injuries caused by their failure to use ordinary care.1California Legislative Information. California Civil Code 1714
What the Plaintiff Must Prove
CACI 400 lists three elements. Every one has to be satisfied before a jury can award damages:
- The defendant was negligent.
- The plaintiff was harmed.
- The defendant’s negligence was a substantial factor in causing the harm.
The instruction folds what lawyers usually call “duty” and “breach” into that first element. Rather than checking those off separately, the jury simply decides whether the defendant was negligent, using the definition supplied by CACI 401. Causation gets its own treatment in CACI 430.2Justia. CACI No 400 Negligence – Essential Factual Elements
How the Jury Decides Whether Someone Was Negligent
CACI 401 gives the jury an objective yardstick. Would a reasonably careful person have acted the same way in the same situation? The defendant’s good intentions, personality, and lack of experience do not enter the analysis. The comparison is to a cautious, ordinary person.3Justia. CACI No 401 Basic Standard of Care
The standard flexes with the risk. Higher-risk activities call for greater precautions. Driving 30 mph on a quiet residential street is different from driving 30 mph through a school zone at dismissal. Jurors weigh the circumstances as they existed at the time, not with hindsight.
Children
Under CACI 402, a child’s conduct is measured against what a reasonable child of the same age would have done in a similar situation. A seven-year-old is not expected to exercise adult judgment.4Legal Information Institute. Standard of Care
Professionals
When the defendant is a doctor, engineer, accountant, or similar professional, the comparison shifts to a competent professional in the same field. That almost always requires expert testimony, because jurors are not expected to know things like the correct protocol for reading an MRI or designing a load-bearing wall. An expert explains the accepted practices, and the jury decides whether the defendant fell short.
Proving Causation
Carelessness alone is not enough. The plaintiff has to tie the carelessness to the injury. CACI 430 uses the substantial factor test: the defendant’s negligence must be something a reasonable person would consider to have contributed to the harm, and it must be more than a remote or trivial factor. It does not have to be the only cause.5Justia. CACI No 430 Causation Substantial Factor
Many negligence cases are won or lost here. Even overwhelming evidence of carelessness will not carry a verdict if the link to the injury is weak. The test also absorbs the traditional “but for” framework: the harm would not have occurred but for the defendant’s conduct.
Multiple Causes
Real injuries rarely have one clean cause. CACI 431 confirms that when the defendant’s negligence combines with some other factor to produce the harm, the defendant cannot escape responsibility just because something else contributed. As long as the defendant’s conduct was a substantial factor, liability attaches.6Justia. CACI No 431 Causation Multiple Causes
Superseding Causes
CACI 432 gives a defendant one way out. If a third party’s independent and unforeseeable conduct was the real reason the plaintiff got hurt, that intervening event can break the chain of causation, and the original defendant may escape liability for what came after. Foreseeability is the pivot. Routine follow-on events, like a treating doctor slightly worsening the injury, do not break the chain. A truly bizarre and unrelated act might.
Shortcuts to Proving Negligence
Negligence Per Se
Sometimes the defendant broke a specific law, and the “reasonably careful person” debate becomes unnecessary. CACI 418 creates a presumption of negligence when someone violates a statute, ordinance, or regulation. If the plaintiff proves the violation and shows it was a substantial factor in causing the harm, the jury is told to find the defendant negligent, unless the defendant justifies the violation.7Justia. CACI No 418 Presumption of Negligence Per Se
The doctrine, rooted in Evidence Code section 669, has four elements. Along with the violation and causation, the plaintiff must show two things the judge typically decides as a matter of law: that the injury resulted from the type of harm the law was designed to prevent, and that the plaintiff belongs to the class of people the law was meant to protect. A building-code fire-safety violation causing a tenant injury fits. A code violation unrelated to fire safety would not support negligence per se in a fire-injury case.
The presumption is rebuttable. Under CACI 420, a defendant can show the violation was reasonable in the circumstances, that the defendant made a genuine effort to comply, that compliance would have created a greater danger, or that an emergency not caused by the defendant’s own misconduct forced the violation. Children who violate a statute can show they exercised the care expected at their age.
Res Ipsa Loquitur
Some accidents point to negligence even when no one can pinpoint what went wrong. CACI 417 lets a plaintiff rely on that inference by proving three things:
- The harm ordinarily would not have happened without someone being negligent.
- The harm was caused by something only the defendant controlled.
- The plaintiff’s own voluntary actions did not cause or contribute to the event.
If the jury finds all three satisfied, it may (but is not required to) infer that the defendant was negligent and that the negligence caused the harm. The instruction is most useful in cases like a surgical sponge left inside a patient or an elevator that suddenly drops. The circumstances do the work the plaintiff cannot.8Justia. CACI No 417 Special Doctrines Res Ipsa Loquitur
Defenses That Reduce or Block Recovery
Comparative Fault
California follows pure comparative fault, so a plaintiff can recover even when mostly at fault. CACI 405 tells the jury that if the defendant proves the plaintiff’s own negligence contributed to the harm, the jury assigns the plaintiff a percentage of responsibility, and the damages award is reduced by that percentage. There is no cutoff threshold.9Justia. CACI No 405 Comparative Fault of Plaintiff
Comparative fault is an affirmative defense. The defendant carries the burden and has to show both that the plaintiff was negligent and that the plaintiff’s negligence was a substantial factor in causing the harm, the same two-part test from CACI 400 pointed the other way.
Primary Assumption of Risk
Certain activities carry inherent dangers, and California law says voluntary participants accept them. Under CACI 470, primary assumption of risk is a complete defense to a negligence claim in sports and recreational activities. A co-participant who is merely careless during a pickup basketball game or a ski run generally owes no duty of care for injuries arising from risks inherent in the activity.10Justia. CACI No 470 Primary Assumption of Risk – Exception to Nonliability
The defense has limits. A plaintiff can still recover by showing the defendant either intentionally caused the injury or acted so recklessly that the conduct fell entirely outside the normal range of the activity. A hard foul in a basketball game is one thing; a punch during a timeout is another. The reckless conduct must also be the kind that could be prohibited without fundamentally changing the sport.
Custom and Practice
CACI 413 lets the jury weigh evidence of how people in a community or industry typically act. If a contractor followed the same framing technique used by every licensed contractor in the area, that fact bears on whether the contractor acted reasonably. Custom gives jurors a real-world benchmark beyond the abstract reasonable person.
Following the crowd is not a guaranteed defense, though. A jury can find that an entire industry’s standard practice falls short of reasonable care. If every restaurant in town stores cleaning chemicals the same unsafe way and a customer is hurt, “everyone does it” does not make it safe. Custom is evidence, not a shield.
Damages
Once liability is established, the jury turns to damages. CACI 3900 instructs the jury to award an amount that will reasonably compensate the plaintiff for each item of harm the defendant’s conduct caused, even if the specific harm could not have been anticipated. The plaintiff does not need to prove an exact dollar figure, but the jury cannot speculate.11Justia. CACI No 3900 Introduction to Tort Damages – Liability Contested
Economic and Noneconomic
Economic damages cover losses with a clear dollar value: medical bills, lost wages, property repair costs, and out-of-pocket expenses like transportation to medical appointments. Receipts, pay stubs, and billing records prove them.
Noneconomic damages compensate for harm without a price tag: physical pain, emotional distress, loss of enjoyment of life, and effects on personal relationships. These are harder to calculate, and juries have wide discretion in setting the amount. California places no statutory cap on noneconomic damages in standard negligence cases, so awards vary widely with the severity of the injury and the strength of the evidence.
Punitive Damages
Ordinary negligence does not support punitive damages. Under Civil Code section 3294, a plaintiff seeking them must prove by clear and convincing evidence that the defendant acted with oppression, fraud, or malice. Malice here means the defendant either intended to cause injury or engaged in despicable conduct with a willful and conscious disregard for the safety of others. That is a significantly higher bar than the carelessness at the heart of a negligence claim.12California Legislative Information. California Civil Code CIV 3294
Deadline to File
Even a strong negligence case dies if it is filed too late. Code of Civil Procedure section 335.1 gives you two years from the date of injury to file a personal injury or wrongful death lawsuit based on negligence.13California Legislative Information. California Code of Civil Procedure 335.1
The clock does not always start on the day of the accident. California recognizes a discovery rule: when an injury is not immediately apparent, the limitations period begins when the plaintiff discovers or reasonably should have discovered the harm. CACI 455 addresses this delayed-discovery scenario for the jury.
Medical malpractice has its own tighter deadline under Code of Civil Procedure section 340.5. The plaintiff must file within three years of the date of injury or one year after discovering it, whichever comes first. Exceptions apply for fraud, intentional concealment, or a foreign object left in the patient’s body, but the outer three-year limit is otherwise firm.14California Legislative Information. California Code of Civil Procedure 340.5