“But-For” v. “Substantial Contributing Factor” — Recent Ruling Addresses Competing Causation Standards

A decision regarding which competing causation standard must apply to medical malpractice cases with multiple tortfeasors has been answered by the Massachusetts Supreme Judicial Court (SJC). In February 2021, the SJC ruled that the traditional “but-for” causation principle is the appropriate standard for torts with multiple defendants.

With this ruling, issued in Doull v. Foster (Case No. SJC-12921; Lower Court Case No. 1478CV00058), the SJC denied the plaintiff’s request for a new trial while affirming the trial court’s instructions to the jury on causation and verdict for the defense.

More critically, their decision clarified that “the substantial test is unnecessarily confusing” and should no longer be used in torts.

Background on the Case: Doull v. Foster

According to court documents, the plaintiff was a middle-aged woman who sought treatment from an internist from 2008 to 2011 for symptoms of perimenopause. Over that time, she was treated by a nurse practitioner and never evaluated by the physician, though both were named as defendants in the case.

During her first appointment, the plaintiff was prescribed “a topically applied, naturally derived progesterone cream.” The nurse practitioner claimed that she discussed alternative treatment options with the plaintiff. However, she admitted that she did not document any discussion she had with the plaintiff regarding the risks of progesterone cream causing blood clots. According to the nurse practitioner, she did not consider the plaintiff to be at risk for this complication.

The plaintiff reportedly used the progesterone cream through the spring of 2011, visiting the internist practice three times that year with complaints of shortness of breath. The nurse practitioner attributed this health issue to the plaintiff’s history of asthma and allergies.

In May 2011, the plaintiff experienced a “seizure-like event.” Upon hospitalization, she was diagnosed with pulmonary embolism (PE), a life-threatening condition in which blood clots block the lung’s pulmonary arteries. Shortness of breath is a hallmark symptom of PE, as well as other conditions. The plaintiff was also diagnosed with chronic thromboembolic pulmonary hypertension (CTEPH) at that time.

Surgical attempts to remove the blockeage were unsuccessful, and the woman ultimately died from CTEPH complications in 2015.

The plaintiff filed a medical malpractice case before her death, with various family members also joining the lawsuit. A representative for her estate, along with the other surviving plaintiffs, filed a motion to amend the case to a wrongful death action in 2015.

The Plaintiffs’ Allegations

The defendants failed to explain the risks of progesterone cream and failed to obtain informed consent from the plaintiff, the complaint alleged. Furthermore, the allegations charged that the defendants failed to diagnosed PE in 2011 when the plaintiff visited the practice multiple times and that the physician failed to properly supervise the nurse practitioner. This negligence, the plaintiffs contended, resulted in the fatal health complications that caused the decedent’s untimely death.

Trial Arguments

The defendants denied all of the allegations, arguing that they provided proper and adequate care. The defense contended that there was no way to prevent the plaintiff’s CTEPH and that the outcome would have been the same, even if the condition had been diagnosed in 2011. Additionally, the defense denied any negligence concerning the physician’s supervision of the nurse practitioner.

The trial commenced on May 28, 2014, before the honorable J. Mary-Lou Rup in the Franklin County Superior Court. Both sides had medical experts testify on causation.

The plaintiffs’ expert, a primary care internal medicine physician, testified that progesterone cream prescribed to and used by the plaintiff likely caused her to develop blood clots. This expert also testified that the nurse practitioner’s failure to diagnose the plaintiff in 2011 could have prevented the onset of CTEPH and that physician’s failure to supervise the nurse practitioner was a breach of his duty of care.

Countering this testimony, a pulmonologist testifying for the defense opined that there was “no evidence anywhere that indicates that progesterone cream applied to the skin increases the risk of clotting.” The defense expert also countered the other points made by the plaintiff’s experts, testifying that CTEPH, as well as the plaintiff’s death, would not have been preventable, even with a 2011 diagnosis of pulmonary embolism, because the disease “had been going on for a long time, probably months at least.”

Jury Instructions & Verdict for the Defense

After both sides presented their case and closing arguments were made, Judge Rup gave the jury the following instructions:

With regard to this issue of causation, the Defendant in question’s conduct was a cause of the Plaintiff’s harm, that is [the plaintiff’s] harm, if the harm would not have occurred absent, that is but for the Defendant’s negligence. In other words, if the harm would have happened anyway, that Defendant is not liable.

The jury, following deliberations, returned a verdict for the defense, finding that:

  1. The defendants did not fail to obtain informed consent from the plaintiffs with regards to the progesterone cream.
  2. While the nurse practitioner was negligent in failing to diagnose the plaintiff’s pulmonary embolism, that negligence did not cause the health events that followed; nor did the failure to diagnose cause the plaintiff’s death.
  3. The internist had been negligent in supervising the nurse practitioner, but that also did not harm the plaintiff or contribute to her fatal health complications.

The Appeal

Following the verdict, the plaintiffs filed a motion for a new trial. Judge Rup denied the motion, and the plaintiffs appealed, alleging errors with the jury instructions and prejudicial errors. Specifically, the plaintiffs argued that the judge should have given the jury instructions based on the substantial contributing factor standard, not the but-for causation standard that the jurors were instructed to follow. The plaintiffs reasoned that the substantial contributing factor standard should be applied in this case because there were multiple defendants.

The defendants disagreed, contending that the proper jury instructions were given, based on Massachusetts state law and the Restatement (Third) of Torts: Liability for Physical and Emotional Harm (2010) (Restatement [Third]).

Due to the nature of the plaintiffs’ objections in the appeal, the Massachusetts Supreme Judicial Court issued a motion to transfer the case from the Appeals Court, taking it up for review due to the alleged prejudicial error.

Causation Standards

Serving as the bedrock of negligence law—and a key point of contention in the jury instructions and the appeal—causation standards for medical malpractice cases and torts, in general, are based on the notion that a defendant cannot be held liable for negligence that does not cause harm to the plaintiffs.

Traditionally, the “but-for” causation standard is applied in tort cases, used to make determinations about the relationship of alleged negligence and the injuries or harm a plaintiff has allegedly suffered.

Through this standard, a defendant is a factual cause of harm if the harm would not have happened “but for” the defendant’s negligence. Put another way, the but-for standard puts a question of necessity on the table—would the harm to the plaintiffs have occurred if not for (but for) the defendant’s conduct?

The “substantial contributing factor” standard considers defendants to be factual causes of harm when their conduct was a “substantial factor” in bringing about that harm. This standard, specific to multiple-defendant cases, has often been invoked in toxic torts.

The Restatement of Torts (Second) explains the substantial contributing factor standard as follows:

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.

High Court Reviews Case, Affirms Use of Traditional But-For Causation Standard

The appeal in Doull v. Foster was argued before the Massachusetts Supreme Judicial Court on Monday, October 5, 2020. About four months later, on February 26, 2021, the SJC ruled to uphold the judgment from the trial court, denying the plaintiff’s request for a new trial and putting an end to this wrongful death case.

The SJC opinion—backed by Chief Justice Kimberly S. Budd, Justice David A. Lowy, Justice Frank M. Gaziano, Justice Elspeth B. Cypher, and Justice Scott L. Kafker— noted that the substantial factor test was “not intended to displace but-for causation more generally” and that if it “is employed whenever multiple causes are alleged, as the plaintiffs argue, the potential for confusion is significant.” This created a real risk that “what originated as an exception to but-for causation would swallow the rule.”

Consequently, the Justices concluded that the but-for standard is the appropriate causation standard to use:

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. Because the jury in this case were instructed using traditional but-for causation principles, the instructions were proper. We also reject all of the plaintiffs’ other claims on appeal and affirm the order denying a new trial.

Notably, Justice Lowy wrote a separate concurring opinion, with Justice Gaziano joining, possibly leaving the door open for the substantial contributing factor standard to be used in the future. Specifically, Justice Lowy opined that:

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.

It remains to be seen whether—or when—a future case will raise a new challenge that invites the debate over the substantial factor test back before the courts. For now, the ruling has established the but-for standard as the gold (and arguably the only) standard of causation in tort cases.

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