Market Share Liability in DES Cases: The Unwarranted Erosion of Causation in Fact

In the final analysis, the legislature, and not the court, is the appropriate forum for determining whether to adopt or reject market share liability

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The Article concludes that market share liability is an unsound concept, that it represents too wide a leap in our tort principles, and that the abrogation of such a fundamental tort requirement is unwarranted. Hand of Justice.


DePaul Law Review,
David M. Schultz,
Volume 40, Article 5,
Issue 3 Spring 1991.

As our society progresses in complexity, theories of tort law have evolved in order to provide redress for the harms caused in a changing world. Tort law evolution has resulted in the creation of new remedies and, in many instances, the erosion of certain preconditions for recovery in tort. Nevertheless, with limited exceptions, there has not been significant erosion of the requirement that a plaintiff must first be able to identify the person or entity that caused her injury before she can recover in tort. In the past decade, however, a small number of courts have abrogated this principle, which is referred to as “causation in fact.” In the place of causation of fact, these courts have adopted the concept of “market share liability.

The market share liability theory has developed mainly through lawsuits filed by women who claim to suffer injuries resulting from their mothers ingestion of the drug Diethylstilbestrol (DES) while pregnant. These plaintiffs are commonly referred to as the “DES daughters.” The time that passes between the maternal ingestion of DES and the diagnosis of the injuries is generally twenty or more years because the injuries do not manifest themselves until sometime after the daughter has reached puberty. A DES daughter is often unable to identify the specific manufacturer of the drug her mother took for two key reasons: the long passage of time and the fungible nature of DES. Faced with the possibility of leaving these plaintiffs without a remedy as a result of their inability to identify the manufacturer, some courts have instead abolished the traditional requirement of establishing causation in fact. In place of causation in fact, these courts have adopted a theory that imposes liability upon any defendant who participated in the manufacturing or marketing of DES in the relevant market. Under this “market share liability” theory, each defendant is liable for the proportion of the judgment that its share of the market represented during the relevant time period.

Market share liability is a flawed concept that likely will apply only to a narrow class of plaintiffs and defendants.

Market share liability has been controversial since its inception. The concept has been adopted with varying modifications by a handful of courts and promoted by a larger number of legal commentators. At the same time, other courts have denounced the theory of market share liability when faced with the opportunity to adopt the proposition in either DES cases or cases involving other products. Currently, only nine state supreme courts have addressed the market share liability issue in a DES case. Most likely, however, other jurisdictions will eventually be forced to face this issue, especially in light of the fact that DES was used nationwide, some plaintiffs have achieved success with the theory, and there is the potential for large recoveries.

Most legal commentary on the issue of market share liability has supported the adoption of the theory. Commentators and courts that support the market share liability theory correctly argue that there is a need to adapt our existing tort law in the face of progress. They also argue that there is strong emotional appeal to insure a remedy for all plaintiffs, especially plaintiffs who are innocent of any wrongdoing. However, this Article contends that courts should not develop a market share liability concept.

  1. This Article begins with a brief history of the development of the drug DES.
  2. In the next section, this Article reviews the tort requirement of causation in fact.
  3. The third section outlines the DES cases in which state supreme courts have adopted market share liability,
  4. and the fourth section addresses cases where courts have rejected the theory in the DES context and in other actions.

Some DES plaintiffs have been able to establish the identity of the specific manufacturer, while others will be able to establish enough evidence to proceed to trial on the issues of causation in fact or negligence.

The Article concludes that market share liability is an unsound concept, that it represents too wide a leap in our tort principles, and that the abrogation of such a fundamental tort requirement is unwarranted. Two ideas are presented to support this conclusion.

  1. First, there is insufficient data to accurately develop the required market shares for each of the hundreds of pharmaceutical companies that produced DES. This lack of data precludes the fair allocation of liability for DES related injuries among all DES manufacturers.
  2. Second, upon close scrutiny, the underlying policies offered to justify adoption of the market share liability theory are either not achieved by the theory, and even if they can be achieved, they do not provide sufficient reasons to adopt it.

This Article proposes that the judicial development of market share liability involves making public policy determinations that more appropriately should be left for state legislatures. A legislative response, similar to the federal legislation established to compensate persons injured by childhood vaccines such as the diphtheria, pertussis, and tetanus (“DPT”) vaccine is a proper method of compensation, and one that will not require a radical change in a state’s tort law.

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