Comparative Fault

Comparative fault (also called comparative negligence) is the predominant modern approach to allocating liability when both the plaintiff and the defendant are at fault. Under this doctrine, the plaintiff's damages are reduced by their percentage of fault, rather than being completely barred as under the traditional contributory negligence rule.

There are two main variants of comparative fault. Pure comparative fault allows the plaintiff to recover damages reduced by their percentage of fault regardless of how great that fault is. Even a plaintiff who is 90% at fault can recover 10% of their damages. Modified comparative fault bars recovery entirely if the plaintiff's fault reaches a certain threshold — either 50% (the "50% bar" rule, where the plaintiff must be less than 50% at fault) or 51% (the "51% bar" rule, where the plaintiff must not be more than 50% at fault).

The shift from contributory negligence to comparative fault represents one of the most significant developments in American tort law. Under the traditional contributory negligence rule, any negligence by the plaintiff — even 1% — completely barred recovery. This harsh result led to doctrines designed to soften its impact, such as last clear chance and the gross negligence exception. Comparative fault eliminated the need for these workaround doctrines by directly addressing the fairness concern: liability should be proportional to fault.

Most jurisdictions adopted comparative fault through legislation, though some courts imposed it judicially. The system interacts with joint and several liability in complex ways. In a modified comparative fault jurisdiction that has also adopted several liability, each defendant pays only their proportionate share of the plaintiff's damages, and the plaintiff's recovery is further reduced by their own percentage of fault. Students must carefully track these interactions on exams.