by Jennifer A. Creedon and Stephanie M. Gazda
In Doull v. Foster, 487 Mass. 1 (2021) (“Doull”), the Supreme Judicial Court (“SJC”) adopted a but-for factual causation standard as set forth in the Restatement (Third) of Torts (2010) and abandoned the substantial contributing factor test in matters involving multiple tortfeasors or multiple causes, except for toxic tort cases.
Doull involved a medical malpractice claim against two medical providers for alleged negligent treatment of the Plaintiffs’ decedent. Dr. Richard Miller and Nurse Practitioner Ann Foster treated Laura Doull from 2008 to 2011. Foster provided Doull with progesterone cream in 2008 to treat perimenopause-related symptoms, which Doull used through the spring of 2011. Between March and May 2011, Doull complained of shortness of breath on three separate occasions, but Foster diagnosed it a symptom of Doull’s allergies and history of asthma. Doull suffered a stroke in May 2011 and another doctor diagnosed her with a pulmonary embolism and chronic thromboembolic pulmonary hypertension (CTEPH), a rare disease impacting the pulmonary artery and heart. Doull, 43 years old, died in 2015 from complications arising from CTEPH. Plaintiffs filed a complaint against Miller and Foster, alleging failure to obtain informed consent as to the potential risks of pulmonary emboli associated with the progesterone cream treatment and failure to properly diagnose and treat Doull for her symptoms of pulmonary emboli, leading to her premature death.
After the close of evidence at trial, the trial judge heard arguments concerning the disputed jury instructions. Plaintiffs argued for the application of the substantial contributing factor test. Under this test, to be found legally responsible for Doull’s injuries, the Defendants’ negligence need only be a substantial contributing factor in bringing about those injuries. Defendants, on the other hand, sought a but-for causation instruction. Under this standard, even if they were found to be negligent, the jury would also have to find that Doull’s injuries would not have occurred but for their negligence. The trial court agreed that the but-for causation standard was the appropriate instruction.
The jury found that the Defendants did not fail to acquire informed consent from Doull regarding the progesterone cream. While the jury did find that Foster negligently failed to diagnose Doull’s pulmonary embolism and Miller failed to properly supervise Foster, it did not find this negligence was the “sole/but-for” cause of harm suffered by Doull under the trial court’s instruction.
The SJC’s Decision
The main issues for the SJC to decide were, in a case involving multiple potential tortfeasors or potential causes of injury, whether the substantial contributing factor test may or must be used in lieu of the but-for standard in the causation jury instructions and whether the court should adopt a “factual cause” of harm standard, as provided in Sections 26 and 27 of the Restatement (Third) of Torts.
The SJC held that the but-for standard is the proper standard in most negligence cases, as it allows the factfinder to separate the necessary causes from other conduct that, although negligent, did not cause harm. Under the Restatement (Third) of Torts, the factfinder can determine whether a tortfeasor is a factual cause even in instances where the cause was small but necessary. The but-for standard does not require that a defendant must be the sole factual cause of harm. Rather, it keeps the focus on whether the harm would still have occurred absent the defendant’s conduct. Where multiple causes are alleged, which is often the case, it is appropriate to instruct a jury that there can be more than one factual cause of harm. By recognizing that multiple causes can exist, the but-for standard precludes the need for substantial contributing factor in the causation analysis.
In this case, the SJC found that the trial court’s but-for instruction to the jury was proper. The jury ultimately determined that the Defendants did not cause Doull’s injuries, despite breaching their duty as medical providers by failing to diagnose the pulmonary embolism, because the evidence showed that the demonstrated harm would have resulted even in the absence of their negligence. Thus, no causal connection existed between the Defendants’ conduct and Doull’s harm.
Despite being accepted and used by Massachusetts courts, the SJC observed that not only does the substantial contributing factor test create confusion as it is both too strict and too lenient, it also invites the factfinder to skip the factual causation inquiry by deciding the negligent conduct is substantial without determining whether it was even the cause of the harm.  Furthermore, it inserts a high degree of subjectivity as to what is substantial.
Although the SJC chose not to extend its decision to toxic tort cases, the Court indicated in a lengthy footnote that it would reconsider the substantial contributing factor test in an appropriate toxic tort case in the future. The SJC acknowledged that, because of the unique features of toxic tort cases, including the number of defendants involved, latency period of the diseases, and exposure from multiple sources, there might be difficulties in using the but-for standard in such cases. Additionally, there might be factual and scientific limitations on a plaintiff’s ability to establish the requisite causal connection between the harm and an individual defendant.
Concurring in the judgment, Justice Lowy, joined by Justice Gaziano, agreed with the outcome of the case. Nonetheless, the concurrence criticized the majority for abandoning decades of precedent to alleviate confusion that does not exist, arguing that the substantial contributing factor test usefully directs the factfinder’s attention to the conduct of the parties in determining legal responsibility. While the but-for test looks at what might have been and whether the harm would have occurred but for a defendant’s conduct, the substantial contributing factor test looks at what actually happened and whether a defendant’s conduct played a role in the result.
Given that the substantial contributing factor test has been used for over 100 years, Doull represents a significant change in Massachusetts tort law. The SJC saw an opportunity to untangle complex causal determinations by eliminating the substantial contributing factor test. Prior to Doull, a court could utilize a jury instruction that encompassed a substantial contributing factor test in lieu of a “but for” test in a multiple tortfeasor case. However, the substantial contributing factor test was never intended to be a wholesale replacement of but-for causation. In this way, Doull represents a return to concepts central to tort law, including the but-for standard. The decision marks an effort by the SJC to have the trial courts give consistent instructions on causation standards, and for the factfinder to determine whether a defendant’s conduct was a cause of the plaintiff’s harm.
 See O’Connor v. Raymark Industries, Inc., 401 Mass. 586, 589 (1988). O’Connor defined the core principles of causation, including substantial contributing factor. Id. at 591-92. The trial court instructed the jury to find whether the plaintiff was exposed to asbestos from the defendant’s product, and if so, determine whether such exposure substantially contributed to the cause of his mesothelioma. Id. at 588-89. The trial court noted that “[i]t doesn’t have to be the only cause, but it has to be a substantial contributing cause. … It means something that makes a difference in the result.” Id. at 589. The jury found that while the plaintiff was exposed to asbestos from the product, such exposure did not substantially contribute to the cause of his mesothelioma. Id. at 587. On appeal, the SJC found that by defining a substantial contributing factor as “something that makes a difference in the result,” i.e., a but-for cause of the plaintiff’s harm, this implied that “the plaintiff had the burden of proving that the defendant’s product contributed in fact” to the eventual outcome “in a legally cognizable manner.” Id. at 592.
 Doull v. Foster, 487 Mass. 1, 10 (2021).
 Section 26 of the Restatement (Third) of Torts: Physical and Emotion Harm (2010) states that negligent conduct must be a factual cause of harm, meaning the harm would not have occurred absent the conduct, in order for one to be held liable. Multiple causes are addressed in Section 27, which provides that “each act is regarded as a factual cause of the harm.” Comment c to Section 27 further explains that if a defendant’s conduct was fully capable of causing the harm, then they cannot escape liability merely because of the existence of another sufficient cause.
 Doull, 487 Mass. at 12, citing Restatement (Third) of Torts, § 26 cmt c.
 Id. at 12-13.
 Id. at 13, n.13. The SJC also refers to the concept of “causal sets” introduced in the Restatement (Third) of Torts, Section 26, cmt. c, which are defined as “the group of actions or conditions that were necessary to bring about the harm.” Id. at 13, n.14. Where the factual harm is an aggregate of multiple causes, the Restatement suggests that it is a causal set. Id.
 Id. at 13.
 Id. at 11-12.
 Id. at 15.
 Id. at 17, n.22.
 Id. at 25, 27.
 Id. at 26-27.
Jennifer A. Creedon is a Partner at Martin, Magnuson, McCarthy & Kenney. Her practice encompasses a wide variety of products liability and business litigation matters. Jennifer authored an amicus brief in Doull v. Foster on behalf of the Massachusetts Defense Lawyers Association (MassDLA).
Stephanie M. Gazda is an associate attorney at Martin, Magnuson, McCarthy & Kenney. Stephanie focuses her practice on toxic tort, products liability, and general liability matters.