Proportional liability in United States

Proportional liability 

At common law the all-or-nothing rule (q.v.) required that a plaintiff have either a full recovery against defendant or none at all. This was seen to have led to substantive injustice in that somewhat negligent defendants would be able to avoid liability entirely – or be implicated for the entirety of the damages plaintiff suffered.

Proportional liability proposes to remedy the all-or-nothing rule by permitting a defendant to be held liable for damages only in proportion to their fault in creating the accident. Thus if the defendant were found only to have contributed to 20 percent of the tort (leaving aside for the moment the question of how that determination is made and whether a sufficient cause can only be partially responsible for a consequence) the defendant would be only liable for twenty percent of the damages. Thus proportional liability often arises in questions of joint and several liability.

Contributory negligence vs. comparative fault

Proportional liability also arises in cases of contributory negligence / comparative fault. At common law the rule of contributory negligence held that if the plaintiff were at all responsible for their misfortune – that is if the plaintiff’s own negligence contributed to the tort – be that contribution ever so small the plaintiff would have no recovery because of the all-or-nothing rule. This rule was also seen to be injust and in some jurisdictions has been replaced with the rule of comparative fault. According to the rule of comparative fault a finding of plaintiff’s negligence will reduce the award of damages to the plaintiff. Thus if plaintiff were ten per cent at fault for creating their injury then the damage award to the plaintiff would be reduced by ten percent.

In cases of products liability liability according to market share and epedemiological proof can be used to avoid the problems of causal indeterminicity – although they raise other problems of indeterminicity and may undermine legal certainty. In those cases proof is obtained via statistical evidence and thus the rationale of proportional liability appears again.

Market share liability

The rationale of proportional liability can arise first in cases where it is known that the plaintiff was injured by a product, but not known which manufacturer created the product. There a proportional market share liability may be applied, at least where it is known that all such products were in fact defective. Thus if plaintiff ingests a defective drug, and a certain corporation has fifteen percent of the market share then the defendant would be fifteen per cent liable for the damages arising out of their injury. See, e.g.

Hamilton v. Beretta U.S.A. Corp., 2001 N.Y. LEXIS 946, *; 96 N.Y.2d 222; 750 N.E.2d 1055; 727 N.Y.S.2d 7 (Market share liability where handgun manufacturer unknown due to negligence of manufacturer).

Epedemiological Proof

The second instance, epedemiological proof, arises where it is certain that the plaintiff was injured but uncertain what the cause was. For example a corporation negligently dumps toxic wastes. As a result the rate of cancer in that zone doubles. Plaintiff might be able to argue that the defendant should be fifty per cent liable for their cancer.