For purposes of market share liability in cases involving diethylstilbestrol, it is probably impossible, with the passage of time, to determine market share with mathematical exactitude. But just as a jury cannot be expected to determine the precise relationship between fault and liability in applying the doctrine of comparative fault or partial indemnity, the difficulty of apportioning damages among the defendant producers in exact relation to their market share does not seriously militate against the rule of market share liability. With regard to the liability of independent tortfeasors, where a correct division of liability cannot be made the trier of fact may make it the best it can.
Two class actions for personal injuries were filed against a company manufacturing diethylstilbestrol (DES). The complaint alleges that the company were jointly and individually negligent in marketing and promoting DES as a safe and efficacious drug to prevent miscarriage, without adequate testing or warning, and without monitoring or reporting its effect. The complainants, daughters who were allegedly injured by their mothers' ingestion of DES, were unable to identify the specific manufacturer of the drugs taken by their mothers. The defendants moved to dismiss the case on this basis, which was approved by the trial court. The case was appealed to the Supreme Court of California.
Was the motion to dismiss properly granted?
In reversing the dismissals the court adopted the theory of market share liability based on the principle that between innocent plaintiffs and negligent defendants the latter should bear the cost of injury. Therefore, once plaintiffs joined the manufacturers of a substantial percentage of DES, defendants were required to prove they could not have manufactured the injury-causing product. Absent such proof, liability for damages could be apportioned based on each defendant's share of the appropriate market.