How Comparative Negligence Works in California Injury Claims

If an insurer or another person says you were partly responsible for an accident, the percentage they give you is not the starting point. It's a conclusion. Before that conclusion can be tested, the person making the allegation should be able to identify what you supposedly did, why that conduct was negligent, and how it contributed to the harm.

California uses pure comparative negligence. Your proven share of responsibility can reduce your damages, but California does not use a rule that automatically bars an injury claim at 50 or 51 percent fault. So if you've read somewhere that being half at fault ends a claim, that is not the rule here. That answers the broad legal question. It does not decide what percentage, if any, the evidence supports in a particular case.

Being partly at fault does not bar a California injury claim.

The California Supreme Court adopted pure comparative negligence in Li v. Yellow Cab Co. The principle is proportional: responsibility is allocated according to fault rather than treated as an all-or-nothing bar.

Here is what a percentage does to the arithmetic, and nothing else. It puts no value on any claim:

That arithmetic assumes the hard part is already done: that damages and the percentage have both been properly determined. In a real dispute, both may be contested, and the figure quoted to you sits on the contested side of that line. California's civil jury instructions direct the factfinder, the jury or judge who decides the case, to determine damages and fault percentages through a defined process; an adjuster's early figure is not a substitute for that process.

Conduct and causation must support the percentage.

California Civil Jury Instruction No. 405 addresses exactly this situation: a defendant's claim that the plaintiff was also negligent. The burden sits with the side making the claim, not with the person it is aimed at. The defendant must prove both that the plaintiff was negligent and that the plaintiff's negligence was a substantial factor in causing the harm. Only then does the instruction call for a reduction based on the percentage of responsibility assigned to the plaintiff.

That two-part requirement is the one worth holding a percentage to. A mistake that had nothing to do with the injury should not be converted into a percentage merely because it sounds unfavorable. Evidence that you were present, that you were distracted at some other time, or that you violated a rule in the abstract does not necessarily establish that the conduct contributed to this event.

A useful analysis asks:

• What specific act or omission is alleged?
• What duty or standard of care is said to apply in those circumstances?
• What evidence supports or contradicts the alleged conduct?
• How is that conduct supposed to have contributed to the collision, event, or injury?
• Is the proposed percentage based on complete evidence, or is it a negotiating position formed before key evidence was obtained?

That is why “you were 30 percent at fault” is not a complete explanation. It's a number without its reasons. The question to send back is, “Thirty percent based on what act and what causal evidence?”

An adjuster's percentage is not a finding.

An insurance adjuster may state a percentage while evaluating or negotiating a claim. That is the carrier's claim position, and a claim position is something you're allowed to disagree with. You or a lawyer acting for you may reject it, ask for its factual basis, or offer a different analysis. If the parties settle, they may resolve the dispute without any court deciding a percentage.

If the dispute is litigated and tried, it is the factfinder, not the adjuster, who applies the governing instructions to the evidence. CACI No. 3960 provides a framework for determining total damages, assigning responsibility percentages, and reducing the plaintiff's award by the plaintiff's percentage. The evidence admitted, the claims presented, and the instructions given in that particular case control the decision.

An adjuster's letter, a police report, a citation, and a jury finding are therefore not interchangeable, however official each one looks on paper. Each comes from a different actor, through a different process, for a different purpose. An early percentage may affect negotiations, but it is not an adjudicated fact simply because it appears in writing.

The overview of how a California personal injury claim works places an insurer's position, negotiation, and a possible lawsuit on their separate tracks.

What you did after the injury is a separate argument from how it happened.

Comparative negligence concerns conduct that helped cause the accident or original injury, which means conduct before or during it. CACI No. 3930 addresses mitigation of damages separately. Mitigation asks whether, after the injury, the plaintiff failed to use reasonable efforts to avoid additional harm and what amount, if any, could reasonably have been avoided. The defendant has the burden on that issue too, under the instruction.

The distinction matters because something you did afterward does not rewrite how the accident occurred. It may raise a separate question about additional loss, but it should not be used casually as proof that you caused the original collision, fall, or other event.

Medical decisions should remain with qualified health professionals. A missed appointment or a gap in your records does not establish mitigation by itself. The legal question concerns the actual recommendation, your circumstances, the reasonableness of an available step, causation, and the additional harm allegedly avoidable.

Each responsible actor requires a separate causal analysis.

If more than one person may have contributed, California's jury instructions allow responsibility to be allocated among multiple actors when the evidence and claims support it. A matter may involve several drivers, a vehicle owner, an employer, a contractor, a property controller, or another person whose conduct allegedly contributed.

Adding a name is not the same as proving fault. For each actor, identify the relevant duty or control, the act or omission supported by evidence, and how that conduct contributed to the harm. CACI No. 406 directs the factfinder to assign percentages totaling 100 percent only after those causal findings are made.

Other rules may affect how particular damages are allocated or collected among multiple defendants. That is a party-specific damages question, not a reason to flatten every comparative-fault dispute into one percentage chart.

Turn an assigned percentage into testable questions.

Do not begin by negotiating against an unexplained number. Convert the assertion into a factual and legal proposition that can be evaluated.

• Ask for the specific conduct the person or insurer attributes to you.
• Ask what evidence supports that account and whether any material evidence remains outstanding.
• Preserve the complete source, not only a selected clip, photograph, or quotation.
• Identify sources that address the same act and time from another angle.
• Separate collision fault from injury causation, the amount of loss, coverage, and mitigation. A dispute in one category does not automatically resolve the others.
• Keep the letter, email, estimate, report, or recorded statement the percentage or allegation arrived in.

If the dispute arose from a vehicle collision, the focused guide on what to do when the other driver blames you addresses the immediate response. The broader guide on evidence to preserve after an injury explains source preservation.

The evidence that would test the percentage is often not in your hands.

The legal task is to turn a conclusion into elements, proof, and a decision. A lawyer can identify the comparative-fault theory, determine who bears the burden, seek evidence outside your own possession, and separate a negotiating position from an allocation the admissible evidence could support. When a percentage rests on disputed facts, or on several people who might have contributed, that is the work, and it is what the firm's personal injury practice is for.

Primary Legal Authorities

• California Courts: 2026 Civil Jury Instructions (opens in a new window), including CACI Nos. 405, 406, 3930, and 3960
• California Courts: Civil Jury Instructions Resource Center (opens in a new window)
• Li v. Yellow Cab Co. (1975) 13 Cal.3d 804 (opens in a new window)

Evaluate the allegation before the number.

Write the proposed percentage at the top of a page. Under it, list the act being alleged, the evidence offered, the causal link claimed, and the material evidence that has not yet been reviewed. That turns a number into questions that can actually be investigated.

To discuss the theory and evidence behind a comparative-fault allegation, request a consultation. Initial consultations with Boyadzhyan Legal Shield are free, confidential, and carry no obligation to hire the firm.