California Comparative Fault, Explained

The rule

The California Supreme Court adopted comparative fault in Li v. Yellow Cab Co. in 1975, replacing the old rule under which any contributory negligence by the plaintiff barred recovery entirely.

Under pure comparative fault, your recovery is reduced in proportion to your own share of responsibility, and it is never eliminated by it. The arithmetic is simple:

• Damages of $100,000, you are 10 percent at fault: you recover $90,000.
• Damages of $100,000, you are 50 percent at fault: you recover $50,000.
• Damages of $100,000, you are 90 percent at fault: you recover $10,000.

That last line is what makes California different. In a modified comparative fault state, being more than 50 or 51 percent at fault bars recovery completely. In a contributory negligence state, being one percent at fault can bar it. Here, a claimant who bears most of the blame still recovers the remainder.

How fault percentages actually get set

There is no formula. In litigation, a jury assigns percentages to each party, including parties who were not sued, after hearing the evidence. Everywhere else, which is to say in the overwhelming majority of claims, the percentage is a negotiated number.

That negotiation starts earlier than most people realize. An adjuster who gets you on the phone in week one and establishes that you were going 'maybe 5 over' or 'glanced at the navigation' has created a discount applied to every offer that follows. It is efficient claims handling and it works, because the statement arrives before anyone has pulled the signal timing, the event data or the video.

What actually moves a fault percentage is evidence, not argument:

• Vehicle event data recorders, showing each vehicle's speed, braking and throttle in the seconds before impact.
• Intersection, business and residential camera footage, usually overwritten within 14 to 30 days.
• Damage geometry on both vehicles, which constrains the possible angles and relative speeds.
• Scene evidence: gouge marks, debris distribution, points of rest, and skid or yaw marks.
• Signal timing data from the agency that operates the intersection.
• Independent witnesses, found and interviewed before memories fade and numbers change.
• Phone records, obtainable in litigation where distraction is suspected.

The comparative fault arguments you should expect

• Speed. Even modest speeding gets offered as a percentage, and it only matters legally if it actually contributed to the collision or its severity.
• Seat belt non-use. California requires belts, and non-use can reduce damages to the extent it worsened the specific injuries. It does not reduce damages that a belt would not have prevented.
• Helmet non-use for motorcyclists, which logically applies to head injuries and not to a fractured tibia, though insurers apply it to everything.
• Pedestrians crossing outside a crosswalk. Still a comparative argument rather than a bar, and since the Freedom to Walk Act took effect in 2023 police generally cannot even cite a pedestrian absent an immediate hazard.
• 'Open and obvious' hazards in premises cases, which reduce an owner's duty to warn without necessarily eliminating the duty to fix.
• Failure to mitigate. Gaps in treatment, skipped physical therapy and not following medical advice get argued as a failure to minimize your own damages, which is a related but separate doctrine.
• Provocation in dog bite cases, asserted far more often than the facts support, particularly where the victim is a child.

When more than one person is at fault

Fault gets apportioned among everyone who contributed, and California treats the two kinds of damages differently once it does.

For economic damages such as medical bills and lost wages, defendants are jointly and severally liable, meaning any one of them can be required to pay the full amount and sort out contribution among themselves. For non-economic damages such as pain and suffering, Civil Code section 1431.2, enacted by Proposition 51, makes each defendant liable only for their own proportionate share.

The practical consequence shows up in multi-vehicle collisions and in cases with an uninsured defendant. If one of three at-fault drivers has no insurance, the economic damages can still be pursued in full against the insured defendants, while the non-economic damages attributable to the uninsured driver's share may be uncollectible. That allocation is worth getting right rather than conceding.