The Massachusetts Supreme Court stated in its opinion filed on February 26, 2021: “In this medical malpractice case, we are asked once again to clarify our case law on causation, along with a series of other issues that are more readily decided. Specifically, we examine the use of two competing causation standards: the traditional but-for causation standard and the alternative substantial contributing factor standard. After careful review, we conclude that the traditional but-for factual causation standard is the appropriate standard to be employed in most cases, including those involving multiple alleged causes. This is the approach recommended by the Restatement (Third) of Torts: Liability for Physical and Emotional Harm (2010) (Restatement [Third]). In doing so, we conclude that the substantial factor test is unnecessarily confusing and discontinue its use, even in multiple sufficient cause cases.”
A defendant cannot be held liable for a harm unless the defendant caused the harm. Causation has traditionally involved two separate components: the defendant had to be both a factual cause (or “cause in fact”) and a legal cause of the harm. Legal causation is also commonly referred to as “proximate causation.” The Restatement (Third) describes this aspect of the causation inquiry as whether the defendant’s conduct was within the “scope of liability.”
Generally, a defendant is a factual cause of a harm if the harm would not have occurred “but for” the defendant’s negligent conduct. This long-standing principle ensures that defendants will only be liable for harms that are actually caused by their negligence and not somehow indirectly related to it. The question is whether the defendant’s conduct was necessary to bringing about the harm.
Additionally, for the defendant to be liable, the defendant must also have been a legal cause of the harm. This means that the harm must have been within the scope of the foreseeable risk arising from the negligent conduct.
Substantial Contributing Factor Causation
A defendant whose tortious act was fully capable of causing the plaintiff’s harm should not escape liability merely because of the fortuity of another sufficient cause. In circumstances in which but-for does not work, defendants were treated as a cause where their conduct was not a necessary but-for cause but was rather a so-called “substantial factor” in bringing about the harm: if 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.
A substantial factor causation was devised to address the specific problem of multiple sufficient causes where but-for causation could not be proved. It was not intended to displace but-for causation more generally. In circumstances other than multiple sufficient causes, but-for causation was required for a defendant to be held liable.
The Massachusetts Supreme Court stated that to be a substantial factor, the defendant also had to be a but-for cause of the harm in most cases. The sole exception to the but-for causation requirement was for multiple sufficient cause cases. “The result was to merge and confuse the but-for standard and the substantial factor test. It also blurred the line between factual and legal causation.”
Multiple Cause Cases
The Massachusetts Supreme Court stated, “the plaintiffs urge, and some of our prior cases suggest, that a substantial contributing factor standard should be used whenever there are multiple potential causes of a harm. We conclude, however, that a but-for standard is the proper standard in most negligence cases, as but-for causes can be identified and conduct that had no causal effect can be excluded … In multiple sufficient cause cases, the existence of two independently sufficient causes means that we cannot identify a but-for cause even though there are multiple tortfeasors who would have caused the harm on their own. In the absence of one of the causes, the other cause would still have been sufficient to bring about the harm.”
“There is nothing preventing a jury from assessing the evidence and determining which of the causes alleged by the plaintiff were actually necessary to bring about the harm, and which had nothing to do with the harm.”
“Indeed, this case shows that the but-for test works well even when a plaintiff alleges that there are multiple causes of a harm. Here, the plaintiffs alleged that the various negligent acts of the defendants caused Doull’s harm and eventual death. The jury were instructed on a but-for standard. As explained above, the purpose of this but-for standard is to separate the conduct that had no impact on the harm from the conduct that caused the harm. The jury ultimately did just that — it concluded that the defendants did not cause the harm even though they committed a breach of their duties by failing to diagnose her pulmonary embolism. Tort law has long made this causal connection a prerequisite for imposing liability. Here, using a but-for standard, the jury concluded that no such connection existed between the defendant’s conduct and Doull’s harm and death. This shows how, even in a case involving multiple causes in which the plaintiffs argue it was error not to use the substantial contributing factor test, the but-for standard did what it is supposed to do and prevented the defendants from being held liable where the jury concluded that they did not cause the harm. Indeed, these types of cases, alleging multiple causes, may be where the but-for test is most important and useful, as it serves to separate the necessary causes from conduct that may have been negligent but may have had nothing to do with the harm caused.”
“[T]here is no limit on how many factual causes there can be of a harm …The focus instead remains only on whether, in the absence of a defendant’s conduct, the harm would have still occurred … And acknowledging the potential for multiple but-for causes “obviates any need for substantial factor as a test for causation” … If a defendant’s conduct was necessary to bring about a harm, and the harm would not have occurred without the defendant’s conduct, that defendant should be treated as a factual cause of the harm.”
“Although terms like “substantial factor” or “substantial contributing factor” would seem to imply some level of causal connection, their employment without a but-for causation instruction in cases in which but-for causation can be established invites the jury to skip this step in the analysis and impose liability on someone whose negligence lacks the requisite causal effect.”
The Massachusetts Supreme Court held: “we conclude that a but-for standard, rather than a substantial factor standard, is the appropriate standard for factual causation in negligence cases involving multiple alleged causes of the harm … Thus, in the majority of negligence cases, the jury should be instructed on factual cause using a but-for standard as well as legal causation … If there must be an exception to but-for causation in cases where the but-for standard fails, we should simply recognize such an exception rather than adopting an entirely different causation standard with confusing terminology and unexpected difficulties.”
Appropriate Jury Instruction
“Therefore, in the rare cases presenting the problem of multiple sufficient causes, the jury should receive additional instructions on factual causation. Such instructions should begin with the illustration from the Restatement (Third) of the twin fires example so that the complicated concept can be more easily understood by the jury. After the illustration, the jury should be instructed, “A defendant whose tortious act was fully capable of causing the plaintiff’s harm should not escape liability merely because of the happenstance of another sufficient cause, like the second fire, operating at the same time.” The jury should then 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 is in operation at the time the plaintiff’s harm occurs, the factual causation requirement is satisfied” … In such cases, where there are multiple, simultaneously operating, sufficient causes, the jury do not have to make a but-for causation finding … we conclude that the substantial contributing factor test should no longer be used in most negligence cases.”
A concurring opinion attached to the majority’s opinion stated, “With so many pages of the Massachusetts Reports already filled with the successful application of the substantial contributing factor test, the court’s conclusion that the test is now unworkable defies experience and unravels precedent. I fear that it does so at the price of fairness.”
Source Doull v. Foster, SJC-12921.
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