State supreme court upends causation in tort law, promising plenty post-pandemic work for lawyers

"Cause and Effect" by Marina Noordegraaf CC BY-NC-SA 2.0

The high court of Massachusetts, in a 3-2 decision, has effected a seismic shift in tort law, adopting on Friday a new approach to legal causation.

The court's holding casts into uncertainty fundamental rules developed over more than a century across the full range of tort liability theories.  Years, even decades of litigation may be required to fully map out the change.

In short, the Massachusetts Supreme Judicial Court rejected the conventional rule of "substantial causation" in favor of analyzing "scope of liability" and "multiple sufficient cause," an approach counseled by the Third Restatement of Torts: Liability for Physical and Emotional Harm (2010), an influential scholarly treatise published by the nonprofit American Law Institute (ALI).  The court ordered the change for only some cases in negligence, but left open the possibility that the change would affect the whole of tort law in the Commonwealth.

Aristotle by Francesco Hayez (1811)

Cause and Effect

Almost every liability in tort law requires causation.  That is, a defendant is only liable when the plaintiff can prove that her or his injury was caused by the defendant.  But the meaning of cause has been famously elusive in law and a subject of multidisciplinary debate for millennia, spanning Aristotle's metaphysical analytics in 4th century B.C. philosophy, St. Thomas Aquinas's meditation on the existence of God in 13th century theology, and the problem of quantum superposition in 21st century physics.

Causation in law is dominated by the concept of "scientific causation," termed informally "but-for cause," and known also as "factual causation."  To recover, a plaintiff must prove causation by showing that but for the conduct of the defendant, the plaintiff would not have been injured or suffered loss.

Scientific causation goes a long way to providing a legal standard, but not all of the way.  Legal scholars have long recognized that the approach has shortcomings, especially in cases of "overdetermined" causation.  That is, the test sometimes fails to indicate causation in the presence of multiple culpable defendants.  The test also sometimes indicates causation for one defendant, of many, whose culpability is so minimal as to be exonerating.

Image by State Farm (CC BY 2.0)

The classic example of improper failure of causation is a plaintiff's home consumed by two converging fires.  The multiple causes of destruction are said to "overdetermine" the harm.  The jury might conclude that but for either fire, the home would have been consumed anyway by the other fire.  Thus, it seems, neither fire is a but-for cause of the destruction.  At best, it is difficult, if not impossible, for the jury to determine whether either fire was a but-for cause.  Yet it cannot be right that the arsonist who started only one of the fires escapes civil liability.  If either fire by itself would have destroyed the home, then each fire is a "sufficient" cause of the destruction, and that standard supports liability.

Pixabay by Gerd Altmann

In rarer cases, but-for causation indicates causation when common sense suggests otherwise.  Imagine that science one day so masters the complexity of weather systems that it can be proved that but for the beating of a carpet on a Cape Town balcony, a hurricane would not have struck New York ("the butterfly effect," like in time travel, but not really).  The carpet beater might be a scientific cause of the hurricane, but we would be reluctant to say that the carpet beater is responsible for the hurricane.  The principle can be extrapolated to physical systems known to contemporary science, such as human pathology.  Consumption of a single cigarette might be proved to have catalyzed cancer in the plaintiff, alongside other causes, such as genetic predisposition and a history of pipe smoking.  But we might not agree that the proven catalysis by itself is a sufficient reason to charge the cigarette seller with civil liability for the whole of plaintiff's suffering.

To better calibrate the rule of causation to tort liability, American tort law in the 20th century developed the concept of "substantial causation," sometimes, if at risk of imprecision, called "legal causation" or "proximate causation."  Liability came to require that the defendant's conduct was a scientific cause and a substantial cause of the plaintiff's injury, or, in rare cases fitting the fire paradigm, a substantial cause indivisible from other sufficient causes, together constituting a scientific cause.

Pixy (CC BY-NC-ND 4.0)

A Substantial Disagreement

The rule of substantial causation attracted adherents and opponents.  Adherents said that the concept worked well, because it is understandable to ordinary people, especially jurors.  Tort law is about enforcement of the unwritten social contract.  We, ordinary members of the society, have a shared intuition about when a scientific cause is as powerful as a home-wrecking fire, justifying declaration of a civil wrong.  Likewise, possessed of common sense, we can recognize a trivial scientific cause as an insufficient basis to impose liability.

Precisely so, opponents responded.  Substantial cause invites a jury to disregard proof of scientific causation and to make moral judgments about responsibility.  The rule employs the hopelessly amorphous standard of substantiality to allow juries and courts to make policy and conceal their hubris with the aroma of equitable legitimacy.

The policy-making potential of legal causation was not lost on lawyers and jurists, many of whom embraced it as socially desirable.  One can argue that civil juries, guaranteed by the Seventh Amendment and heralded by Alexis de Tocqueville, if mocked by Mark Twain and Dave Chappelle, are the inspired mechanism with which America democratically injects public policy into the civil trial.

Pixy (CC BY-NC-ND 4.0)

And although causation devolves to the jury as a question of fact, a court has the power to obviate the need for an expensive jury trial when a question cannot be decided but one way by ordinary minds.  In such circumstances, the question is said to be decided as a matter of law.  Thus, substantiality was termed "legal causation" and offered grounds for a judge to dismiss a case, rather than let the liability question reach the jury.

Judges might be more or less bold or overt in how they exercise power through legal causation, depending on how their jurisprudential philosophies regard the propriety of judicial policy-making.  In a highly regarded paper in 1983, economically minded scholars William Landes and Richard Posner suggested that if the facts of a case point erroneously toward a politico-economically inefficient result, "cause comes to the rescue."  In other words, the rule of legal causation empowers the court to direct the outcome and "the optimal result to be achieved."  (Both Landes and Posner are affiliated with the University of Chicago Law School, known for its commitment to law and economics; Justice Kafker earned his law degree there.)

A Third Way

Substantiality detractors got the better of the argument when the ALI drafted the Third Restatement in the 20-aughts.  The authors did not take policy and pragmatism wholly out of the judicial process, but sought to abate confusion about where they reside by moving them.  The Third Restatement approach moves "legal causation" from the "cause" element of negligence into a new inquiry, "scope of liability."  The similarly ancillary function of the "duty" element of negligence also was moved and merged at this new address, though that's a blog post for another day (and a question left open by the Massachusetts ruling).  The new approach means to give judge and a jury a place to circumscribe defendant liability exposure without the semantic gamesmanship arguably required by the conventional analysis of causation and duty.

The restatement project is often criticized for seeking to progress the law rather than merely restate it.  The line is finer than it might seem.  On this point, one certainly can say that the authors intended to change the law of the states.  At the same time, it's equally defensible to say that the authors sought to help the states to clarify the law, that is, to better state, or restate, what they were doing already.

Pulmonary embolism by Baeder-9439 (CC0 1.0)

A Tale of Two Causes

The case before the Court in Massachusetts involved the death of a patient and two instances of medical malpractice.  Plaintiff Laura Doull died from complications of chronic thromboembolic pulmonary hypertension, or CTEPH.  The jury determined that a nurse practitioner was negligent in failing to diagnose Doull with a pulmonary embolism in 2011, and that Doull's doctor was negligent in supervision of the nurse practitioner.  However, the jury also determined that neither instance of negligence was a but-for cause of Doull's death from CTEPH; in other words, Doull's death was a consequence of her illness and not of anything the nurse practitioner and doctor did, right or wrong.  The defendants were not responsible.

On appeal, the plaintiff argued, among other theories, that the trial judge had not instructed the jury properly.  The trial court had instructed the jury on but-for causation, but not on substantial causation.  All five justices who heard the case for the Supreme Judicial Court affirmed the judgment for the defendants.  The court was unanimous in holding that the plaintiff's case must fail, because the jury determined that but-for causation failed.  First, there was no need for the jury to consider legal causation when there was no factual causation.  Second, this case was not about two fires converging on a house.  Though a consequence of two actors, there was only one misdiagnosis.

Justice Kafker

In a majority opinion authored by Justice Scott Kafker and joined by Chief Justice Kimberly Budd and Justice Elspeth Cypher, the court reached the sweeping conclusion that the Commonwealth adopts the Third Restatement approach to causation.  The change makes no difference in the instant case, because but-for causation still is required under the Third Restatement approach, in fact is the nub of what remains in the causation element, legal cause having been removed to scope of liability.  The concurrence, authored by Justice David Lowy and joined by Justice Frank Gaziano, would not have changed the Commonwealth's approach to causation, but would have ruled that the omission of the substantiality instruction was harmless error.

The plaintiff's argument predicated on failure to instruct on substantiality played into the majority's position on the Third Restatement.  Recall that critics of substantiality contend that it invites jurors to disregard scientific evidence and reach a liability determination despite the failure of but-for causation.  Because but-for causation was required, and the jury found it absent, the plaintiff's plea of error suggests that an instruction on legal causation should have been permitted to obfuscate the jury's view of factual causation.  "What originated as an exception to but-for causation would swallow the rule," the majority wrote.  The old approach "blurred the line between factual and legal causation," indeed, "conflates and collapses the concepts of factual and legal causation." 

Image by johnny-automatic (CC0 1.0)

In most cases, the court majority concluded, the but-for instruction on causation alone is sufficient, even when there are multiple potential causes.  "There is nothing preventing the 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," the majority reasoned, and the jury did just that in the instant case.  As to the paradigmatic two-fire scenario, the court wrote that

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.

(Footnote and citation omitted; paragraph breaks added.)  The majority also noted, likewise as counseled by the Third Restatement, that a jury may be admonished to disregard trivial causes to redress the rare problem of a false positive in but-for causation.

Justice Lowy

Cross Concurrence and Tort Retort

The concurrence disagreed sharply over the abandonment of substantial causation, and the text of the opinion hints at a heated debate.  "Today the court abandons decades of precedent in an attempt to clarify confusion that does not exist," Justice Lowy opened.  "Abandoning the substantial contributing factor instruction in circumstances where there is more than one legal cause of an injury will, in my view, inure to the detriment of plaintiffs with legitimate causes of action while not clarifying the existing law of causation."

Substantiality has long been the rule for clarity in cases of multiple potential causes, Justice Lowy explained.  It was the approach of the Second Restatement, published in 1965, and before it, the First Restatement, published in 1939, and appeared in Massachusetts case law as early as 1865.  

The test has endured because it works, Justice Lowy reasoned.  The "counterfactual framing" of the but-for test, compelling the jury to imagine a reality in which a defendant's conduct did not occur, paints only half a picture and risks misleading the jury.  In multiple-cause cases, counterfactuals "invite the jury to get caught up in speculative combinations of 'what if' and 'if only,'" Justice Lowy wrote.  "In the sorts of byzantine fact patterns that often arise in medical malpractice, toxic tort, and other tort cases with multiple causes, an instruction on but-for causation provides defendants with tools unavailable to plaintiffs," such as blaming a party not on trial (civil "Plan B").

Pixabay by b0red

The substantiality test "focus[es] jurors' attention" inversely: "it frames causation to have a juror start by considering what actually happened, and whether the defendant's actions played a part in producing the result."  The instruction "focuses the jurors ... directly on what ought to determine legal responsibility: the conduct of the parties."

The concurrence accused the majority of "abandon[ing] what has been our steady and successful practice" of instruction on substantiality.  "Why the sudden about-face?" the concurrence asked rhetorically, then answered: "Only one thing has changed: the Restatements."  In the majority's reasoning, the concurrence observed, "citations to our cases drop off.  Instead, the court replicates an abstract and academic discussion of the problems that the Restatement (Third) of Torts found with the standard" (footnotes omitted).

In footnotes, the concurrence suggested that any confusion results from the Third Restatement's cross-jurisdictional comparison, which omits Massachusetts, and observed, citing Hawaii, that other states have continued to test for substantiality in the decade since the Third Restatement appeared.

The majority responded in its footnotes.  The Third Restatement approach has not been adopted nowhere.  The Iowa Supreme Court adopted the Third Restatement in 2018, the majority noted.

Pixy (CC BY-NC-ND 4.0)

Referencing judicial confusion over multiple causes, the majority noted: "For an example of this confusion, look no further than the concurrence."  The majority disputed the concurrence's conclusion that the Third Restatement approach favors defendants.  And the majority rebutted the concurrence's assertion that the substantiality test has been working: "Beyond the concurrence's own appraisal of the situation, it is not clear what evidence, empirical or otherwise, there is that the use of the standard has been 'steady and successful.' ....  Indeed, when forced to decide what standard to use, the experienced and capable trial judge in this case observed, 'Well ... I know that the law has been somewhat confused in some people's eyes ....'"

The majority took umbrage at the concurrence's suggestion that the court would change Commonwealth law simply to pursue the lead of the Restatement.

The concurrence minimizes the numerous extensive critiques of the substantial factor test....  The concurrence also suggests that we are somehow simply following academic fashion in adopting the Restatement (Third).  This statement ignores that the substantial factor test originated with the Restatement and that the case law the concurrence cites ... has demonstrated great respect for the development of the law as reflected by the Restatement of Torts....  We turn to the Restatement not because it is fashionable to do so, but because the American Law Institute has struggled greatly with the complicated question of causation in negligence cases and is constantly trying to improve the legal standard in this area, including recognizing its own errors in this regard.

Justice Kafker is a member of the ALI.

"The Restatements are owed respect," Justice Lowy retorted.  "Our cases, however, deserve more."

But What About

I'm not a fan of change.  The worst part of all of this for me is that from here on out, I am going to have to teach Massachusetts torts students two versions of attenuated duty and causation, which already is the longest and hardest chapter of the textbook.  Am I going to get more credit-hours to cram it all in?  No.  Am I going to get paid more to prep more?  Definitely no.  And then there are the unanswerable questions.

Asbestos shingles by Mary Lotus (CC BY-SA 3.0)

The instant case arose in medical malpractice, though the majority extended the new causation rule through negligence.  Or most of it.  The court explicitly declined to apply the new rule in cases of toxic torts, at least for now.  Toxic tort cases, such as asbestos claims, are similar to multiple-sufficient-cause cases in that it is difficult, if not impossible, for a jury to trace a plaintiff's illness to one causal agent, one asbestos producer, even while it seems likely that defendants, asbestos producers, collectively are responsible.

In a very few jurisdictions, this problem has led to a controversial approach to liability based strictly on a defendant's share of the product market.  Massachusetts has not gone that far, but has loosened the causation requirement, essentially allowing substantiality to overwhelm scientific causation.  That approach becomes problematic, now, in light of the court's abandonment of substantiality.

Because the but-for test "seem[s] ill-suited" for toxic-tort cases, the majority opined in a footnote:

It is simply not clear whether the concerns we have with the substantial contributing factor test justify eliminating it in these cases.  Given the volume of these 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.

Pot, kettle, the concurrence wrote.  "For all its purported confusion, the [substantiality] standard continues to work well in toxic tort cases—except for the fact that the court also invites in a footnote overturning what it otherwise praises."

In fact, the problem is bigger than toxic torts, and bigger than a law professor's woes.  The problem of this decision's scope extends to all of tort law.

Remember, a plaintiff in civil litigation must prove causation to recover.  That's not a rule of only medical malpractice, nor a rule of only negligence.  It's a rule of all torts.  All torts require causation.  The elements of conventional negligence, duty, breach, causation, and injury, are the elements of all torts, stripped of factual context, unexcepted by special circumstances: the fundamental particle components of a compensable civil wrong.  

Photo by Phil Roeder (CC BY-NC-ND 2.0)

Thus, again in a footnote, the concurrence hinted at a parade of horribles: "[A]dopting a new approach to cause-in-fact issues in torts will encourage litigants to press for its application in other areas of the law beyond negligence, such as commercial disparagement, defamation, and false representation."  I earlier mentioned an arsonist; basic intentional torts require causation, too.  The problem of causation is so not confined to negligence that the concept of "foreseeability" is used loosely to flesh out legal causation and, simultaneously and alternatively, to locate and describe the outer bounds of the civil liability system in total.

So, tort lawyers, on your marks....

The case is Doull v. Foster, No. SJC-12921 (Feb. 26, 2020).  Justice Dalila Wendlandt and Justice Serge Georges, Jr., were sworn into the court in December 2020 and did not participate in the decision.