Comparative negligence, or non-absolute contributory negligence outside the United States, is a partial legal defense that reduces the amount of damages that a plaintiff can recover in a negligence-based claim, based upon the degree to which the plaintiff's own negligence contributed to cause the injury. When the defense is asserted, the factfinder, usually a jury, must decide the degree to which the plaintiff's negligence and the combined negligence of all other relevant actors both contributed to cause the plaintiff's damages. It is a modification of the doctrine of contributory negligence which disallows any recovery by a plaintiff whose negligence contributed even minimally to causing the damages.
Prior to the late 1960s, however, only a few states had adopted the system. When comparative negligence was adopted, three main versions were used. The first was called "pure" comparative negligence. A plaintiff who was 90% to blame for an accident could recover 10% of his losses. (Of course, defendants who suffered injuries in such a case could counter claim and recover 90% of losses from the other party.)
The second and third versions are lumped together in what is called "modified" comparative negligence. One variant allows plaintiffs to recover "only" if the plaintiff's negligence is "not greater than" the defendant's (the plaintiff's negligence must not be more than 50% of the combined negligence of both parties).
The other variant allows plaintiffs to recover "only if" the plaintiff's negligence is "not as great as" the defendant's (the plaintiff's negligence must be less than 50% of the combined negligence). The apparently minor difference between the two modified forms of comparative negligence is thought by lawyers handling such cases to be significant, as juries who ordinarily assign degrees of fault are much less willing to award damages to a plaintiff who is equally at fault than to one who is less at fault than the defendant.
Contributory negligence doctrine
Some states, though, still use the contributory negligence doctrine to evaluate negligence in a tort. For instance, Alabama, Maryland, North Carolina, Virginia, and Washington, DC continue to use contributory negligence.
Neither comparative negligence nor contributory negligence should be confused with joint and several liability, which generally holds each of two or more culpable defendants responsible for all the damages sustained by a plaintiff. For practical reasons, a plaintiff who faces the defense of comparative negligence may wish to join all potentially culpable defendants in his action since the plaintiff's negligence will be balanced against the combined negligence of all defendants in apportioning damages even if the plaintiff may not be able actually to get compensation from some of them: for example, if an insolvent individual and a major corporation were both negligent in causing plaintiff's harm.