Market share liability is a legal doctrine

Legal doctrine

A legal doctrine is a framework, set of rules, procedural steps, or test, often established through precedent in the common law, through which judgments can be determined in a given legal case. A doctrine comes about when a judge makes a ruling where a process is outlined and applied, and allows...

 unique to the law of the United States

Law of the United States

The law of the United States consists of many levels of codified and uncodified forms of law, of which the most important is the United States Constitution, the foundation of the federal government of the United States...

 that allows plaintiff

Plaintiff

A plaintiff , also known as a claimant or complainant, is the term used in some jurisdictions for the party who initiates a lawsuit before a court...

s injured by fungible

Fungibility

Fungibility is the property of a good or a commodity whose individual units are capable of mutual substitution, such as crude oil, wheat, precious metals or currencies...

 products to apportion liability

Legal liability

Legal liability is the legal bound obligation to pay debts.* In law a person is said to be legally liable when they are financially and legally responsible for something. Legal liability concerns both civil law and criminal law. See Strict liability. Under English law, with the passing of the Theft...

 among the manufacturers according to their share of the market for the injurious product.

Origins

Market share liability was introduced in the California case Sindell v. Abbott Laboratories. In Sindell, the plaintiffs were injured by DES

Diethylstilbestrol

Diethylstilbestrol is a synthetic nonsteroidal estrogen that was first synthesized in 1938. Human exposure to DES occurred through diverse sources, such as dietary ingestion from supplemented cattle feed and medical treatment for certain conditions, including breast and prostate cancers...

, a drug prescribed to prevent miscarriage. The mothers of the plaintiffs had taken DES while pregnant, and expert testimony showed this to be a proximate cause

Proximate cause

In the law, a proximate cause is an event sufficiently related to a legally recognizable injury to be held the cause of that injury. There are two types of causation in the law, cause-in-fact and proximate cause. Cause-in-fact is determined by the "but-for" test: but for the action, the result...

 of reproductive tract cancers in the plaintiffs years later. The plaintiffs, however, could not ascertain which drug company distributed the DES taken by their mothers. The court responded by allowing the plaintiffs to apportion liability among the defendant drug companies according to their respective shares in the DES market.

Subsequent cases

Sindell required plaintiffs to join defendant drug companies in a single action, and this requirement was modified in the Wisconsin case Collins v. Eli Lilly Co. In Collins, the plaintiff could bring a cause of action against a single defendant, and the burden of proof would be shifted to the defendant to show that they did not produce the DES taken by the plaintiff's mother.

Efforts to expand the market share approach beyond DES cases have been mostly rejected. Courts have declined to expand the market-share approach to asbestos

Asbestos

Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...

 (Becker v. Baron Bros.), handguns (Hamilton v. Beretta), and lead paint (Santiago v. Sherwin Williams Co.). The market-share approach has been expanded to cases involving MTBE in the New York case In re Methyl Tertiary Butyl Ether.