A defendant sued for negligence can answer with legal defenses. Common ones are the plaintiff's own negligence, assumption of the risk, and an expired statute of limitations. Saying "I didn't mean to hurt anyone" is not a defense, because negligence is unintended harm caused by carelessness.
When the plaintiff's own carelessness helped cause the injury, two doctrines compete:
Contributory negligence: all-or-nothing. If the plaintiff's negligence contributed to the harm in any degree, recovery is barred.
Comparative negligence: the plaintiff's recovery is reduced by the plaintiff's own share of fault.
California uses pure comparative negligence. In Li v. Yellow Cab Co. (1975), the California Supreme Court replaced the contributory negligence doctrine with comparative negligence in its pure form: liability is assessed in proportion to fault even when the plaintiff is as much at fault as the defendant, or more. The 50% cutoff used in modified comparative systems does not apply in California.
Computing the payment, with $80,000 of damages:
California (pure comparative), plaintiff 25% at fault: $80,000 × 75% = $60,000.
California, plaintiff 70% at fault: $80,000 × 30% = $24,000. More fault does not bar recovery.
A state that still uses contributory negligence, plaintiff only 5% at fault: $0.