The Massachusetts Supreme Court recently issued a decision in Doull v. Foster in which it adopted the “but-for” standard for causation in negligence cases. The Court held that the but-for test is the appropriate standard for Massachusetts courts to employ in the vast majority of negligence cases involving multiple alleged causes of harm, almost completely eliminating the substantial factor test for causation. It did, however, carve out from that standard cases with multiple sufficient causes, such as asbestos and other toxic tort matters, due to the difficulty in establishing “which particular exposures were necessary to bring about the harm.” [Doull at p. 14]. The Court did, however, leave open the possibility that it may also replace the “substantial factor” test in those cases as well.  This potential for a new rule has created tremendous uncertainty as to the appropriate causation standard for toxic tort cases in Massachusetts moving forward.

Causation is a central component of proof in a negligence case, as only those whose acts of negligence are causally related to a plaintiff’s harm can be liable. A defendant must typically be both a factual cause, or cause in fact, as well as a legal cause of the harm, commonly referred to as proximate cause, in order to be liable for a negligent act or omission. But-for causation is generally established if but-for the defendant’s negligence, the resulting harm would not have occurred. The substantial factor test, on the other hand, is an exception to the traditional “but-for” test used in circumstances where there are potentially multiple alleged causes of the harm. The substantial factor test provides, in those situations, that a defendant is liable if the defendant’s alleged negligence was a “substantial factor” in bringing about the harm. Specifically, the Second Restatement of Torts provides, “[i]f two forces are actively operating, one because of the actor’s negligence, the other not because of any misconduct on his part, and each of itself is sufficient to bring about harm to another, the actor’s negligence may be found to be a substantial factor in bringing it about.” Restatement (Second) §432 (2) [quoted in Doull at p. 14]. The Court recognized that “the terminology was devised to address the specific problem of multiple sufficient causes where but-for causation could not be proved.” [Id.]

The problem with the substantial factor test, according to the Court, is that it “conflates and collapses the concepts of factual and legal causation” and invites jurors to skip the necessary step in their analysis of determining factual causation. See Doull at 24-25. “Absent a but-for requirement, a jury presented with negligence that is ‘substantial’ may decide to impose liability without coming to terms with whether the negligence was even the cause of the harm.” Id. That may lead to a causation finding against a defendant “whose negligence lacks the requisite causal effect.” See Doull at 24. Accordingly, the Court held that the but-for standard, and not the substantial factor test, should be applied in negligence cases with multiple alleged causes of harm.

One notable exception to that ruling, however, is for toxic tort cases. In those cases, particularly asbestos cases, many courts, including the Massachusetts Supreme Judicial Court, have applied the substantial factor test for causation, based on a recognition that it is difficult for plaintiffs to prove “but for” causation because it may be impossible to pinpoint which particular exposure brought about the harm. [Doull at 14]. The Court distinguished such cases as involving “multiple sufficient causes” where a plaintiff claims that: 1) a toxic substance or asbestos caused the harm; and 2) defendants exposed the plaintiffs to a toxic substance or asbestos; however, it is not possible to determine which exposures were necessary to cause the alleged harm. [Doull at 15]. Consequently, courts have adopted a less demanding standard of causation to avoid what the courts deem an unjust result.

Although the Court characterized the application of the “but for” test in toxic tort and asbestos cases as “impossible,” the Court did not endorse the substantial factor test, and in fact, indicated that the Court may consider whether to replace the substantial factor test in those cases as well.   The Court stated that “[t]here appears to be a variety of approaches taken in these cases, and a decision on whether to replace the substantial contributing factor test would benefit from full briefing and argument.” [See Doull at 29, n. 21]. The Court made clear, however, that “[o]ur hesitance [to eliminate the substantial factor test for toxic tort cases], however, should not be taken as a continuing endorsement of the substantial factor approach in toxic tort cases given the concerns we have expressed today.” [Id.] The concerns expressed by the Court in relation to the application of the appropriate causation standard in asbestos and other toxic tort litigation matters are real. As the Court points out, asbestos and other toxic tort litigation matters present unique features including “factual and scientific limitations” that complicate establishing causation.  However, all litigants involved in asbestos and other toxic tort matters face uncertainty as to an alternative standard that could be applied to their cases.

Unfortunately, despite its concerns about the substantial factor test, the Court did not have an opportunity to analyze the causation standard in connection with asbestos and other toxic tort cases to determine if a new standard should be applied to those cases. While the Court clarified the appropriate standard for causation to be applied in most negligence cases, it was reluctant to do so in the context of toxic tort cases. The Court expressed its hesitance to endorse the substantial factor test in those cases, hinting that that the Court may replace the standard if it has an opportunity to review the issue specifically for those cases. The Court’s clarification in most negligence cases; therefore, will undoubtedly create confusion and unpredictability for the litigants involved in asbestos and other toxic matters for the foreseeable future. While the SJC chose not to address the application of the substantial factor test in the context of this case, it certainly signaled that it is open to supplanting substantial factor as the causation test for toxic tort cases. The question remains, however, whether the Court would entertain but-for causation, or whether it may find some middle ground between but-for and substantial cause.