Massachusetts eliminates the Substantial Contributing Factor Test of Causation in Virtually All Cases, Except Toxic Torts

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The Massachusetts Supreme Judicial Court recently issued its opinion in Doull v. Foster, reversing decades of precedent by eliminating the alternative test of factual causation, the “substantial contributing factor” test,  in virtually all types of tort cases in favor of the traditional “but for” test. Doull v. Foster, 2021 WL 843203 (February 26, 2021).   For the time being, the SJC left the test intact for certain types of multiple cause cases, namely toxic tort and asbestos cases.  Even in those cases, however, the court admonished the trial courts and the bar, “”Given the volume of [toxic tort and asbestos] cases, their great importance, and the idiosyncrasies that make them unique with regard to factual causation, it would be unwise to apply our holding to these cases as well without first having the benefit of full briefing and argument.  Our hesitance, 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 at fn. 22.  

Like the Third Restatement, the SJC noted that the substantial factor test had not withstood the test of time and offered no clear guidance on causation, permitting factfinders to “engage in fuzzy headed thinking” about causation. Id at *7.  The test’s terminology allowed a standard that is simultaneously both  too strict and too lenient. Id.  The test’s confusion often encouraged jurors “to skip the factual causation inquiry altogether.” Id. at 8. The Court noted that the use of the substantial factor test “conflates and collapses the concepts of factual and legal causation”, infecting the causation test with policy considerations. Id.  The Court stated that requiring a substantial factor test in any case involving multiple potential causes of injury would result in the “exception to but-for causation… swallow[ing] the rule.” Id.

The SJC reviewed the history of the substantial factor test and its recent rejection in the Restatement [Third] of Torts.  Historically, the substantial contributing factor test, which the Court referred to as an “alternative” theory of causation, was developed to address a single specific type of multiple sufficient cause case.  The Court referred to the classic “twin fires” problem studied by all first year law students.   In such cases two causes of the plaintiff’s damage, each of which would have been sufficient alone to induce the loss, combine to produce the harm.  Because each cause was sufficient in and of itself, neither could be said to be the “but for” cause.  The substantial contributing factor test was designed to “avoid this unjust result” under the traditional test.          

Over the years, however,  courts, led astray by the first two Restatements, began to combine “the substantial contributing factor terminology and the but-for requirement in a confusing manner.” The two tests, never intended to be brought together, were merged. The “but for” test had always been adequate to address even most multiple cause cases, including the multiple sufficient cause cases.  Id at *9.  Going forward the SJC instructed trial courts that,  in “rare cases presenting the problem of multiple sufficient causes”, the court must provide “additional” instructions on factual causation.  The jury should first be instructed with the familiar “twin fires” illustration of causation.  The jury must further be instructed that when “there are two or more competing causes, like the twin fires, each of which is sufficient without the other to cause the harm and each of which was in operation at the time the plaintiff’s harm occurs, the factual causation requirement is satisfied.”  This instruction merely “supplements the but-for standard without conflicting with it.” Id. at *10.

In the end, the Massachusetts Supreme Judicial Court concluded, “[T]he substantial contributing factor test should no longer be used in most negligence cases.”  Having relegated that alternative causation test to the annals of history in most cases, future litigation will determine if it survives in its one remaining habitat—toxic tort litigation—or if it becomes extinct there as well.


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