Title: Doull v. Foster
Citation: N/A
Docket Number: SJC-12921
State: Massachusetts
Issuer: Massachusetts Supreme Court
Date: February 26, 2021

NOTICE:  All slip opinions and orders are subject to formal 
revision and are superseded by the advance sheets and bound 
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error or other formal error, please notify the Reporter of 
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SJC-12921 
 
SETH DOULL1 & another2  vs.  ANNA C. FOSTER & another.3 
 
 
 
Franklin.     October 5, 2020. - February 26, 2021. 
 
Present:  Budd, C.J., Gaziano, Lowy, Cypher, & Kafker, JJ. 
 
 
Negligence, Medical malpractice, Causation, Standard of care.  
Medical Malpractice, Standard of care, Consent to medical 
treatment.  Practice, Civil, Instructions to jury, 
Amendment of complaint, Interrogation of jurors. 
 
 
 
 
Civil action commenced in the Superior Court Department on 
May 28, 2014. 
 
 
The case was tried before Mary-Lou Rup, J., and a motion 
for a new trial was considered by her. 
 
 
The Supreme Judicial Court on its own initiative 
transferred the case from the Appeals Court. 
 
 
 
Krzysztof G. Sobczak for the plaintiffs. 
 
Tory A. Weigand for the defendants. 
 
Jennifer A. Creedon & Stephanie M. Gazda, for Massachusetts 
Defense Lawyers Association, amicus curiae, submitted a brief. 
                    
 
 
1 Individually, as personal representative of the estate of 
Laura Doull, and as next friend of Troy Doull. 
 
 
2 Megan Doull. 
 
 
3 Robert J. Miller. 
2 
 
 
Brendan G. Carney, Thomas R. Murphy, Kevin J. Powers, & 
Elizabeth N. Mulvey, for Massachusetts Academy of Trial 
Attorneys, amicus curiae, submitted a brief. 
 
 
 
KAFKER, J.  Causation has been a continually contested 
concept in tort law, confounding courts, commentators, and 
practitioners.  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.  
Because the jury in this case were instructed using traditional 
but-for causation principles, the instructions were proper.  We 
3 
 
also reject all of the plaintiffs' other claims on appeal and 
affirm the order denying a new trial.4 
 
1.  Background.  We summarize the facts that could have 
been found by the jury, reserving certain facts for later 
discussion. 
 
a.  Facts.  Between 2008 and 2011, Laura Doull was a 
patient of Anna C. Foster, a nurse practitioner, and her 
supervisor, Dr. Richard J. Miller (collectively, the 
defendants).  Miller, an internist, owned the medical practice 
where Doull was a patient. 
 
In August 2008, Doull had an appointment with Foster to 
seek advice regarding perimenopause-related symptoms.  Foster 
prescribed Doull a topically applied, naturally derived 
progesterone cream to treat the symptoms.5  Foster admitted that 
she did not document any conversation that she had with Doull 
about the risks and benefits of, or the alternatives to, the 
progesterone cream, but she did testify that they discussed 
alternatives to it.  However, Foster stated that she did not 
                    
 
 
4 We acknowledge the amicus briefs submitted by the 
Massachusetts Academy of Trial Attorneys and the Massachusetts 
Defense Lawyers Association. 
 
 
5 Progesterone is a hormone that humans naturally produce.  
Supplementing the progesterone that the human body produces is a 
form of hormone replacement therapy typically used to treat 
menopause- or perimenopause-related symptoms.  Progesterone 
supplements come in both synthetic and naturally derived forms. 
4 
 
discuss the possibility with Doull that the progesterone cream 
could cause blood clots because she did not consider this to be 
a risk.  Doull continued to use the progesterone cream through 
the spring of 2011. 
 
Earlier that spring, Doull had visited Miller's practice on 
three separate occasions to complain about shortness of breath.  
Doull met with Foster on each visit, and Foster performed a 
physical examination of Doull each time.  Doull had a history of 
asthma and allergies.  At the spring 2011 visits, Foster 
diagnosed Doull's shortness of breath as a symptom of some 
combination of these long-standing conditions.  Miller did not 
examine Doull during any of these visits. 
 
In May 2011, Doull had a "seizure-like event" and was 
transported to the hospital.  At the hospital, she was diagnosed 
with a pulmonary embolism, a condition where blood clots or 
other substances block portions of the pulmonary arteries in the 
lungs.  A pulmonary embolism may cause shortness of breath as 
well as chronic thromboembolic pulmonary hypertension (CTEPH), a 
rare disease where pressure in the pulmonary artery increases 
and causes the heart to fail.  Indeed, that May, Doull was 
diagnosed with CTEPH.  A lung scan revealed that blood clots in 
Doull's lungs were chronic. 
 
In November 2011, Doull underwent surgery in an attempt to 
remove the blockage from her lungs, but the procedure proved 
5 
 
unsuccessful.  After the surgery, Doull was prescribed various 
medications to treat the pulmonary hypertension that had 
resulted from her CTEPH.  None of these medications abated the 
disease.  In 2015, Doull died from complications arising from 
CTEPH.  She was forty-three years old. 
 
b.  Procedural history.  Prior to her death, Doull and 
various family members (collectively, the plaintiffs) commenced 
this suit against the defendants, claiming negligence, failure 
to obtain informed consent, and loss of consortium.6  Four months 
before trial, the plaintiffs moved to amend their complaint to 
include the manufacturer of the progesterone cream, Women's 
International Compounding Inc. (WIC), as a defendant.  The trial 
judge denied the plaintiffs' motion. 
 
At trial, the plaintiffs argued that Miller and Foster 
failed to obtain informed consent from Doull concerning the 
progesterone cream's risks and alternatives, that Foster failed 
to diagnose Doull's pulmonary embolism during the spring 2011 
visits, and that Miller failed to supervise Foster adequately 
during all relevant times. 
 
To support these claims, Dr. Paul Genecin, a primary care 
internal medicine physician and the plaintiffs' expert witness, 
testified that natural progesterone was not any safer than 
                    
 
 
6 Doull's estate continued to prosecute the claims after her 
death, amending the complaint to add a wrongful death claim. 
6 
 
synthetic derivations of the hormone, and that the cream likely 
caused Doull to develop blood clots.  Genecin also testified 
that Foster had failed to investigate adequately Doull's 
shortness of breath complaints during the spring 2011 visits.  
He testified that diagnosis of Doull's pulmonary embolism during 
the spring of 2011 could have prevented the onset of CTEPH, and 
that Miller's failure to supervise Foster's actions constituted 
a breach of the duty of care. 
 
Dr. Nicholas S. Hill, a pulmonologist and an expert for the 
defense, testified that there was "no evidence anywhere that 
indicates that progesterone cream applied to the skin increases 
the risk of clotting."  Hill also disagreed with Genecin's 
assessment that Doull's CTEPH would have been preventable had 
Foster diagnosed it during the spring 2011 visits.  
Specifically, Hill testified that by the time Doull was 
diagnosed with CTEPH in May 2011, the disease "had been going on 
for a long time, probably months at least."  According to Hill, 
the chronic nature of Doull's blood clots meant that her outcome 
would have remained the same had Foster diagnosed her with the 
disease during the spring of 2011. 
 
The jury returned a verdict for the defendants and answered 
various special questions.  First, the jury found that the 
defendants had not failed to acquire informed consent from Doull 
with respect to the progesterone cream.  Second, although the 
7 
 
jury did find that Foster negligently failed to diagnose Doull's 
pulmonary embolism, they found that this negligence was not the 
cause of either the harms suffered by Doull after her seizure-
like event in 2011 or her death in 2015.  Finally, the jury 
found that Miller had been negligent in his supervision of 
Foster, but that this negligence, too, had not harmed Doull. 
 
Before the jury returned its verdict, the defendants filed 
a motion to require judicial approval for postverdict contact 
with jurors, which the judge granted.  After the verdict, the 
plaintiffs filed a motion for a new trial, which the judge 
denied.  The plaintiffs then appealed.  We transferred the case 
from the Appeals Court to this court on our own motion. 
 
2.  Discussion.  "We review the denial of a motion for a 
new trial for an abuse of discretion, bearing in mind that a 
judge should exercise his or her discretion only when the 
verdict is so greatly against the weight of the evidence as to 
induce in his [or her] mind the strong belief that it was not 
due to a careful consideration of the evidence, but that it was 
the product of bias, misapprehension or prejudice" (quotation 
and citation omitted).  DaPrato v. Massachusetts Water Resources 
Auth., 482 Mass. 375, 377 n.2 (2019). 
 
a.  Jury instructions.  "In a civil trial, a judge should 
instruct the jury fairly, clearly, adequately, and correctly 
concerning principles that ought to guide and control their 
8 
 
action" (quotation and citation omitted).  DaPrato, 482 Mass. at 
383 n.11.  "The judge is not bound to instruct in the exact 
language of the [parties'] requests, however, and has wide 
latitude in framing the language to be used in jury instructions 
as long as the instructions adequately explain the applicable 
law" (quotation and citation omitted).  Id.  When reviewing jury 
instructions, an "appellate court considers the adequacy of the 
instructions as a whole, not by fragments" (citation omitted).  
Id. 
 
The plaintiffs argue that they are entitled to a new trial 
based on several allegedly erroneous jury instructions regarding 
the defendants' negligence.  We consider these claims in turn. 
 
i.  Jury instructions on causation.  The plaintiffs claim 
that the judge's instruction on the element of causation was 
erroneous.  The judge instructed the jury using a but-for 
standard for factual causation.  Specifically, the judge 
instructed: 
"With regard to this issue of causation, the Defendant in 
question's conduct was a cause of the Plaintiff's harm, 
that is Laura Doull'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 plaintiffs argue that the judge was required to instruct the 
jury on a substantial contributing factor standard, instead of 
this but-for standard, because there were several possible 
9 
 
causes of -- and multiple tortfeasors involved in -- Doull's 
injuries and death.  The defendants disagree, contending that 
the instruction given was consistent with both Massachusetts law 
and the approach taken by the Restatement (Third).7  Because the 
plaintiffs objected to the instruction given by the trial judge, 
we review for prejudicial error.  DaPrato, 482 Mass. at 384. 
 
We conclude that the but-for standard was the appropriate 
standard in this case and therefore there was no error.  We also 
clarify infra how a jury should be instructed on causation in 
negligence cases involving multiple potential causes of harm. 
A.  But-for causation.  We begin with basic causation 
principles.  It is a bedrock principle of negligence law that a 
defendant cannot and should not be held liable for a harm unless 
the defendant caused the harm.  See Wainwright v. Jackson, 291 
Mass. 100, 102 (1935) ("The general rule is that one cannot be 
held liable for negligent conduct unless it is causally related 
to injury of the plaintiff").  See also Glidden v. Maglio, 430 
Mass. 694, 696 (2000) (causation "is an essential element" of 
proof of negligence).  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.  See 
Leavitt v. Brockton Hosp., Inc., 454 Mass. 37, 45 (2009) 
                    
 
 
7 We also solicited amicus briefs on whether to adopt the 
factual causation standard from the Restatement (Third). 
10 
 
("Liability for conduct obtains only where the conduct is . . . 
a cause in fact of the injury and where the resulting injury is 
within the scope of the foreseeable risk arising from the 
negligent conduct"); Kent v. Commonwealth, 437 Mass. 312, 320 
(2002), citing Wallace v. Ludwig, 292 Mass. 251, 254 (1935) 
(negligent conduct must be both "cause in fact of the injury" as 
well as "legal cause of the injury").  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."  See Restatement (Third) § 26 comment a (explaining 
terminology changes from prior Restatements). 
Generally, a defendant is a factual cause of a harm if the 
harm would not have occurred "but for" the defendant's negligent 
conduct.  See W.L. Prosser & W.P. Keeton, Torts § 41, at 265 
(5th ed. 1984) ("An act or an omission is not regarded as a 
cause of an event if the particular event would have occurred 
without it").  See, e.g., Hollidge v. Duncan, 199 Mass. 121, 124 
(1908) (affirming determination that plaintiff's injuries would 
not have occurred "but for the defendant's negligence").  See 
also Reporters' Note to Restatement (Third) § 26 comment b 
(collecting authorities demonstrating that "but-for test is 
central to determining factual cause").  This long-standing 
principle ensures that defendants will only be liable for harms 
11 
 
that are actually caused by their negligence and not somehow 
indirectly related to it.  See Callahan v. Cardinal Glennon 
Hosp., 863 S.W.2d 852, 862 (Mo. 1993) ("Any attempt to find 
liability absent actual causation is an attempt to connect the 
defendant with an injury or event that the defendant had nothing 
to do with.  Mere logic and common sense dictate[] that there be 
some causal relationship between the defendant's conduct and the 
injury or event for which damages are sought").  See also 
Paroline v. United States, 572 U.S. 434, 452 (2014) ("If the 
conduct of a wrongdoer is neither necessary nor sufficient to 
produce an outcome, that conduct cannot in a strict sense be 
said to have caused the outcome"); Price Waterhouse v. Hopkins, 
490 U.S. 228, 282 (1989) (Kennedy, J., dissenting) ("Any 
standard less than but-for . . . represents a decision to impose 
liability without causation").  Another way to think about the 
but-for standard is as one of necessity; the question is whether 
the defendant's conduct was necessary to bringing about the 
harm.  Restatement (Third) § 26 comment b ("a factual cause can 
also be described as a necessary condition for the outcome").  
The majority of courts around the country and all three 
Restatements have required but-for causation in most cases.  See 
Reporter's Note to Restatement (Third) § 26 comment a.  See also 
Restatement (Third) § 26; Restatement (Second) of Torts § 432(1) 
12 
 
(1965) (Restatement [Second]); Restatement of Torts § 432(1) 
(1939). 
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."  Leavitt, 454 Mass. at 
45.  This aspect of causation is "based on considerations of 
policy and pragmatic judgment."  Kent, 437 Mass. at 320–321, 
quoting Poskus v. Lombardo's of Randolph, Inc., 423 Mass. 637, 
640 (1996).  These considerations are separate and distinct from 
factual causation.  Kent, supra at 320.  And, together, these 
concepts identify which defendants can be held liable for 
negligent conduct.  This case focuses primarily on factual 
causation. 
 
B.  Exceptions to but-for causation.  There are several 
situations in which a but-for standard does not work and has 
been altered to avoid unjust and illogical results.  See 
Paroline, 572 U.S. at 452 ("tort law teaches that alternative 
and less demanding causal standards are necessary in certain 
circumstances to vindicate the law's purposes").  One is the 
situation involving multiple sufficient (or overdetermined) 
causes.  See Restatement (Third) § 27 comment b ("Courts and 
scholars have long recognized the problem of overdetermined harm 
-- harm produced by multiple sufficient causes -- and the 
13 
 
inadequacy of the but-for standard for this situation").  The 
classic example involves two separate fires merging and 
destroying a house.  See generally Anderson v. Minneapolis, St. 
Paul & Sault Ste. Marie Ry. Co., 146 Minn. 430 (1920).  If 
either fire could have independently destroyed the home, then 
neither fire could be a but-for cause of the harm (because the 
home would have been destroyed by the other regardless), thereby 
relieving each of liability under a but-for standard.  To avoid 
this unjust result, there must be a different causation standard 
in these cases.  See Restatement (Third) § 27 comment c ("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").  These cases, 
however, are exceedingly rare.  Id. at § 27 comment b. 
The first two Restatements devised an alternative causation 
standard, with its own terminology, to address this specific 
problem.  In circumstances in which but-for did not work, they 
treated defendants 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.  Specifically, they provided 
that "[i]f 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 
14 
 
substantial factor in bringing it about."  Restatement (Second) 
§ 432(2).  The substantial factor terminology has, as explained 
infra, proved confusing, as it seems odd to describe something 
that may not have been a cause at all as a substantial factor.  
Nonetheless, the terminology 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.  Id. at § 432(1). 
A number of courts, including this one, have also 
recognized the difficulty of proving but-for causation in toxic 
tort and asbestos cases.  See O'Connor v. Raymark Indus., Inc., 
401 Mass. 586, 588-591 (1986); Morin v. AutoZone Northeast, 
Inc., 79 Mass. App. Ct. 39, 42 (2011).  See also, e.g., 
Rutherford v. Owens-Ill., Inc., 16 Cal. 4th 953, 958 (1997); 
Bostic v. Georgia-Pac. Corp., 439 S.W.3d 332, 353 (Tex. 2014).  
In these cases, it can be difficult, if not impossible, for the 
plaintiff to identify which particular exposures were necessary 
to bring about the harm.  See Matsuyama v. Birnbaum, 452 Mass. 
1, 30 (2008);8 O'Connor, supra, at 588-589; Welch v. Keene Corp., 
                    
 
8 Contrary to the concurrence's suggestion, we certainly are 
not suggesting here that Matsuyama is an asbestos or toxic tort 
case, as the sentence preceding the citation makes clear.  For 
15 
 
31 Mass. App. Ct. 157, 162 (1991).  It may be clear that a toxic 
substance or asbestos caused the harm, and that the defendants 
exposed the plaintiffs to the toxic substance or the asbestos, 
but it may not be possible to determine which exposures were 
necessary to cause the harm.  In this situation, as in multiple 
sufficient cause cases, the but-for standard is inadequate, as 
it could allow all defendants to avoid liability despite their 
negligent exposure of the plaintiffs to the substances, as it 
may not be possible to prove which exposures were necessary to 
bring about the harm and which were not.  The substantial factor 
test again fixes this problem by relaxing the causal requirement 
and permitting liability in these circumstances. 
Instead of limiting the substantial factor test to these 
two contexts where but-for causation cannot be established, 
however, the first two Restatements combined the substantial 
factor terminology and the but-for causation requirement in a 
confusing manner.  The term "substantial factor" was employed 
generally in negligence cases.  In other words, a defendant 
                    
 
the sake of clarity, here is the language to which we are 
referring in Matsuyama -- "The 'substantial contributing factor' 
test is useful in cases in which damage has multiple causes, 
including but not limited to cases with multiple tortfeasors in 
which it may be impossible to say for certain that any 
individual defendant's conduct was a but-for cause of the harm 
. . . ." (emphasis added).  Matsuyama, 452 Mass. at 30.  This is 
the point we are making here as well, which is why we included a 
citation to Matsuyama. 
16 
 
could not be liable for negligence under the first two 
Restatements unless the defendant was a "substantial factor" in 
bringing about the harm.  See Restatement (Second) § 431; 
Restatement of Torts § 431.  But to be a substantial factor, the 
defendant also had to be a but-for cause of the harm in most 
cases.  See Restatement (Second) § 432(1); Restatement of Torts 
§ 432(1).  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.  See Restatement (Third) § 29 
comment a ("The 'substantial factor' requirement . . . in the 
Second Restatement of Torts has often been understood to address 
proximate cause, although that was not intended"). 
C.  Multiple cause cases.  Against this background, 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. 
There is a significant difference between multiple 
sufficient cause and toxic tort cases and other cases involving 
multiple potential causes.  In multiple sufficient cause cases, 
17 
 
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.  Similarly, 
in toxic tort cases, although but-for causation may be 
theoretically sound, it is nearly impossible for a plaintiff or 
a jury to determine with any certainty which exposures were 
necessary to bring about the harm and which were not.  Using a 
strict but-for standard in these cases may frustrate the ability 
of plaintiffs to recover for negligent conduct that caused their 
harm, because of the happenstance of multiple defendants 
engaging in negligent acts each of which alone may be sufficient 
to cause the harm, and the impossibility of proving which of the 
negligent acts were but-for causes.  Thus, if anyone is to be 
held liable for these harms, there must be an exception to the 
but-for standard.  The concern uniting these two types of cases 
is the great difficulty, if not impossibility, of identifying 
but-for causes of the harm. 
This concern is not present in most cases involving 
multiple alleged causes, however.  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.  
18 
 
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.9  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.10  This shows how, even in a case involving multiple 
                    
 
9 The judge instructed the jury that "[the] conduct was a 
cause of the Plaintiff's harm, that is Laura Doull'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." 
 
 
10 Indeed, as described above, the defendants' expert 
testified that Doull's outcome would not have been different 
even if Foster had diagnosed her condition in May 2011.  The 
jury appear to have credited this testimony, as it would explain 
why the jury concluded that Foster, despite her negligence, did 
not cause Doull's harm.  In this way, expert testimony will 
often be significant in cases involving multiple potential 
causes, as it will help the jury distinguish between causes that 
were necessary to bring about the harm and causes that were not. 
 
19 
 
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. 
 
One source of confusion is the mistaken belief that there 
can only be a single but-for cause of a harm.11  Indeed, the 
plaintiffs argue that the presence of multiple potential causes 
here means that no one cause could be the "sole/but-for" cause.  
But there is no requirement that a defendant must be the sole 
factual cause of a harm.  See Reporters' Note to Restatement 
(Third) § 26 comment c ("That a party's tortious conduct need 
only be a cause of the plaintiff's harm and not the sole cause 
is well recognized and accepted in every jurisdiction").  See 
also, e.g., Bostock v. Clayton County, 140 S. Ct. 1731, 1739 
(2020) ("[But-for causation] can be a sweeping standard.  Often, 
                    
 
11 For an example of this confusion, look no further than 
the concurrence.  The concurrence thinks that by instructing the 
jury that there could be more than one but-for cause, we are 
creating a whole new standard separate and apart from the but-
for standard -- a "but-for plus" standard.  See post at    . 
20 
 
events have multiple but-for causes"); June v. Union Carbide 
Corp., 577 F.3d 1234, 1242 (10th Cir. 2009) ("A number of 
factors [often innocent] generally must coexist for a 
tortfeasor's conduct to result in injury to the plaintiff. . . . 
That there are many factors does not mean that the defendant's 
conduct was not a cause"). 
 
In fact, there is no limit on how many factual causes there 
can be of a harm.  Restatement (Third) § 26 comment c ("there 
will always be multiple . . . factual causes of a harm, although 
most will not be of significance for tort law and many will be 
unidentified").  The focus instead remains only on whether, in 
the absence of a defendant's conduct, the harm would have still 
occurred.  See id. ("The existence of other causes of the harm 
does not affect whether specified tortious conduct was a 
necessary condition for the harm to occur").  This is not a high 
bar.  See id. at § 26 comment i ("Quite often, each of the 
alleged acts or omissions is a cause of the harm, i.e., in the 
absence of any one, the harm would not have occurred").  And 
acknowledging the potential for multiple but-for causes 
"obviates any need for substantial factor as a test for 
21 
 
causation."  Reporters' Note to Restatement (Third) § 26 
comment j.12,13 
 
The terminology of the substantial factor standard also 
leads to confusion.  See Restatement (Third) § 26 comment j 
("The substantial-factor test has not, however, withstood the 
test of time, as it has proved confusing and been misused").  
See also Sanders, Green, & Powers, The Insubstantiality of the 
"Substantial Factor" Test for Causation, 73 Mo. L. Rev. 399, 430 
(2008) (substantial factor test "gives no clear guidance to the 
factfinder about how one should approach the causal problem" and 
"permits courts to engage in fuzzy-headed thinking about what 
                    
 
 
12 Where multiple causes are alleged, it is appropriate to 
instruct a jury that there can be more than one factual cause of 
a harm. 
 
 
13 The Restatement (Third) introduces a novel concept 
referred to as "causal sets," see Restatement (Third) § 26 
comment c.  This concept is suggested as a helpful way to think 
of factual causation in a multiple cause case.  It is not a 
separate test and is meant to be used only if it is deemed to be 
helpful.  It is not an independent legal requirement.  A causal 
set is defined as the group of actions or conditions that were 
necessary to bring about the harm.  Id. ("[C]onceive of a set 
made up of each of the necessary conditions for the plaintiff's 
harm.  Absent any one of the elements of the set, the 
plaintiff's harm would not have occurred").  So, in cases where 
the factual cause of a harm is an aggregate of multiple acts, 
omissions, or conditions, the Restatement simply labels the 
aggregate as a "causal set."  It also explains that there may be 
competing causal sets.  See id. at § 27 comment f.  Importantly, 
it does not change the standard of causation -- a defendant 
would still only be a factual cause if the harm would not have 
occurred but for the defendant's actions. 
22 
 
sort of causal requirement should be imposed on plaintiffs" 
[emphasis omitted]).  Unsurprisingly, it has "few supporters."  
Reporters' Note to Restatement (Third) § 26 comment j.14 
The drafters of the most recent Restatement concluded that 
the confusing terminology has rendered the substantial factor 
test potentially both too strict and too lenient as a standard 
                    
 
14 Indeed, as the Restatement points out, many scholars have 
criticized the substantial factor test.  See, e.g., Dorsaneo, 
Judges, Juries, and Reviewing Courts, 53 S.M.U. L. Rev. 1497, 
1528-1530 (2000) (substantial factor "render[s] the causation 
standard considerably less intelligible"); Fischer, Insufficient 
Causes, 94 Ky. L.J. 277, 277 (2005) ("Over the years, courts 
also used the substantial factor test to do an increasing 
variety of things it was never intended to do and for which it 
is not appropriate. . . .  [T]he test now creates unnecessary 
confusion in the law and has outlived its usefulness"); 
Robertson, The Common Sense of Cause in Fact, 75 Tex. L. Rev. 
1765, 1776 (1997) ("By using the term ["substantial factor"] in 
three different senses, the Restatement [Second] of Torts has 
contributed to a nationwide confusion on the matter"); 
Stapleton, Legal Cause:  Cause-in-Fact and the Scope of 
Liability for Consequences, 54 Vand. L. Rev. 941, 945, 978 
(2001) ("The obfuscating terminology of legal cause, proximate 
cause, and substantial factor should be replaced . . ."); 
Wright, Once More into the Bramble Bush:  Duty, Causal 
Contribution, and the Extent of Legal Responsibility, 54 Vand. 
L. Rev. 1071, 1080 (2001).  See also H.L.A. Hart & T. Honoré, 
Causation in the Law 124 (2d ed. 1985) ("Little, however, seems 
to be gained by describing, even to a jury, such cases in terms 
of the admittedly indefinable idea of a 'substantial factor'"); 
W.L. Prosser & W.P. Keeton, Torts § 41, at 43-45 (5th ed. Supp. 
1988) ("Even if substantial factor' seemed sufficiently 
intelligible as a guide in time past, however, the development 
of several quite distinct and conflicting meanings for the term 
'substantial factor' has created a risk of confusion and 
misunderstanding, especially when a court, or an advocate or 
scholar, uses the phrase without indication of which of its 
conflicting meanings is intended"). 
23 
 
of factual causation.  See Restatement (Third) § 26 comment j.  
The use of the word "substantial" imposes a more demanding 
standard than a traditional but-for standard.  The current model 
jury instruction in Massachusetts explains that "substantial" 
means that the defendant's negligence was "not an insignificant 
factor" and that "it must be a material and important ingredient 
in causing the harm."  Massachusetts Superior Court Civil 
Practice Jury Instructions § 4.3.4(b) (Mass. Cont. Legal Educ. 
3d ed. 2014).  There may be policy reasons to impose a more 
rigorous standard for factual cause than but-for causation, but 
that was not the primary purpose of the substantial factor test.  
See Restatement (Third) § 26 comment j.15  Limits on liability 
have also been considered to be properly addressed through the 
lens of legal causation, not factual 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, 
                    
 
 
15 The concurrence argues that the substantial contributing 
factor standard enhances the fairness of a negligence trial.  
Post at    .  We are not sure why this is true, particularly 
from the injured party's perspective, if both factual and legal 
causation are otherwise satisfied.  The injured party has 
suffered a harm, and but for the defendant's conduct the harm 
would not have occurred.  Regardless, we historically address 
the equities of recovery in the legal causation, not the factual 
causation, inquiry.  See Kent, 437 Mass. at 320–321. 
24 
 
that defendant should be treated as a factual cause of the 
harm.16 
Conversely, the confusing terminology has been found to 
invite jurors to skip the factual causation inquiry altogether.  
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.17  See Reporters' Note to Restatement 
(Third) § 26 comment j (substantial factor test "may unfairly 
permit proof of causation on less than a showing that the 
tortious conduct was a but-for cause of harm").  Absent a but-
for requirement, a jury presented with negligence that is 
"substantial" may decide to impose liability without coming to 
                    
 
 
16 If the cause is truly trivial, it can be excluded from 
legal causation on that ground.  See Reporters' Note to 
Restatement (Third) § 26 comment j.  See also Restatement 
(Third) § 36.  Again, the Restatement (Third) approach is more 
straightforward, as it allows a jury to excuse a defendant from 
liability on legal causation grounds where the defendant's 
conduct is determined to be trivial.  See Restatement (Third) 
§ 36. 
 
 
17 In fact, we indicated in O'Connor, 401 Mass. at 591, that 
in a case where a substantial contributing factor instruction is 
given, it would be error for the judge to instruct the jury in a 
way that requires it to find that the defendant was a but-for 
cause of the harm. 
25 
 
terms with whether the negligence was even a cause of the harm. 
As determining causation may be even more difficult where 
multiple causes are alleged, we need to be sure juries do not 
skip this step. 
The use of substantial factor language also conflates and 
collapses the concepts of factual and legal causation.  See, 
e.g., Strassfeld, If . . . :  Counterfactuals in the Law, 60 
Geo. Wash. L. Rev. 339, 355 (1992) (substantial factor approach 
"smuggles noncausal policy considerations, which normally are 
confined to the duty or proximate cause analysis, into the 
analysis of factual causation," and thus it "is either 
contentless, or it reintroduces and complicates [factual 
causation]").  See also Reporters' Note to Restatement (Third) 
§ 26 comment a ("The conflation of factual cause and proximate 
cause by the Torts Restatements has been criticized since 
shortly after the first Restatement of Torts was published").  
Instructing the jury to only consider "substantial factors" as 
causes inserts a high degree of subjectivity as to what is 
substantial and what is not, precisely the types of policy 
considerations that animate our legal causation jurisprudence.  
Such considerations, therefore, should not be incorporated into 
the factual causation analysis as well. 
If the substantial factor test is employed whenever 
multiple causes are alleged, as the plaintiffs argue, the 
26 
 
potential for confusion is significant.  Plaintiffs often allege 
multiple causes of a harm.  Restatement (Third) § 26 comment i 
("Frequently, plaintiffs allege that multiple tortious acts or 
omissions caused their harm.  This is especially true in 
negligence actions because of the flexibility of the reasonable-
care standard").  Moreover, defendants may inject further 
complexity by alleging that the plaintiffs, another defendant, 
or a nonparty caused the harm.  If a substantial factor 
instruction is required whenever there is more than one 
potential cause, then the substantial factor standard could 
supplant the but-for standard as the primary standard for 
factual causation.  What originated as an exception to but-for 
causation would swallow the rule. 
Finally, using a different causation standard in multiple 
cause cases puts trial judges in difficult positions.  Despite 
the apparent overlap, these are different standards.  There is 
no simple, workable definition of "multiple causes" given that 
many cases will involve multiple potential causes.  Using the 
substantial contributing factor test in this manner would mean 
that judges would have to decide which instruction is 
27 
 
appropriate before instructing the jury, a task rife with 
difficulty and potential error.18 
In sum, although the substantial factor test has proved 
useful in two specific situations, it has not been widely 
adopted as the causation standard in all negligence cases and 
has been abandoned by the Restatement itself.  See Restatement 
(Third) § 26 comment a.19 
In light of the foregoing, 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.  We see no reason 
                    
 
18 The concurrence disagrees with our assessment, saying 
instead that we are "abandon[ing] . . . our steady and 
successful practice of applying substantial contributing factor 
in torts cases involving all sorts of fact patterns."  Post at    
.  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."  
Our review of the record here supports our concern that having 
two standards places trial judges in a difficult position 
regarding jury instructions.  Indeed, when forced to decide 
which 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 . . . following the 
Matsuyama decision." 
 
 
19 It appears that the majority of jurisdictions -- over 
two-thirds -- require proof of but-for causation in the majority 
of cases.  At least one jurisdiction has replaced the 
"substantial factor" standard with the Restatement (Third) 
approach.  See Thompson v. Kaczinski, 774 N.W.2d 829, 839 (Iowa 
2009). 
28 
 
to depart from but-for causation in these cases.20  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.  In this case, the judge did exactly that, making the 
instructions proper. 
D.  Eliminating the substantial contributing factor test.  
In addition to not extending the substantial factor test to all 
cases involving multiple causes, there is good reason to replace 
it with the standard proposed in the Restatement (Third) for 
                    
 
20 The concurrence minimizes the numerous extensive 
critiques of the substantial factor test.  To counteract all of 
this criticism, it relies on a passing positive reference to the 
standard as "useful" in dictum in Matsuyama, 452 Mass. at 30, 
which was focused on the utility of the standard when but-for 
causation cannot be established.  As we have explained today, 
however, but-for causation works perfectly well in most cases, 
including those involving multiple causes. 
 
The concurrence also suggests that we are somehow simply 
following academic fashion in adopting the Restatement (Third).  
See post at    .  This statement ignores that the substantial 
factor test originated with the Restatement and that the case 
law the concurrence cites, including Matsuyama, has demonstrated 
great respect for the development of the law as reflected by the 
Restatements of Torts.  See, e.g., O'Connor, 401 Mass. at 591-
592 (citing Restatement [Second] §§ 430, 431, and 433); Bernier 
v. Boston Edison Co., 380 Mass. 372, 386 (1980) (citing 
Restatement [Second] § 435); Quinby v. Boston & Me. R.R., 318 
Mass. 438, 444 (1945) (citing Restatement of Torts §§ 431 and 
433); Vigneault v. Dr. Hewson Dental Co., 300 Mass. 223, 229 
(1937) (citing Restatement of Torts § 432).  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. 
29 
 
multiple sufficient cause cases.21  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.  The approach proposed 
by the Restatement (Third) does exactly that.  See State v. 
Tibble, 790 N.W.2d 121, 127 n.2 (Iowa 2010) (Restatement [Third] 
                    
 
21 The issue of causation in toxic tort and asbestos cases 
is not before us in this case.  Therefore, we do not disturb our 
decision in O'Connor or the use of the substantial contributing 
factor instruction in those cases.  In an appropriate case, 
however, we may consider whether to replace the substantial 
contributing factor test in these cases as well.  There appears 
to be a variety of approaches taken in these cases, and a 
decision on whether to replace the substantial contributing 
factor test would benefit from full briefing and argument. 
 
The concurrence misunderstands the court's hesitance to 
abandon the substantial contributing factor test in asbestos and 
other toxic tort cases.  As we have explained, because of the 
unique features of these cases, there may be factual and 
scientific limitations on a plaintiff's ability to establish the 
requisite causal connection between the harm and an individual 
defendant.  Thus, a but-for standard has seemed ill-suited for 
such cases. 
 
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. 
30 
 
§ 27 is "straightforward rule" in multiple sufficient cause 
cases). 
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.22  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 
                    
 
22 That illustration is as follows: 
 
"Rosaria and Vincenzo were independently camping in a 
heavily forested campground.  Each one had a campfire, and 
each negligently failed to ensure that the fire was 
extinguished upon retiring for the night.  Due to unusually 
dry forest conditions and a stiff wind, both campfires 
escaped their sites and began a forest fire.  The two 
fires, burning out of control, joined together and engulfed 
Centurion Company's hunting lodge, destroying it.  Either 
fire alone would have destroyed the lodge.  Each of 
Rosaria's and Vincenzo's negligence is a factual cause of 
the destruction of Centurion's hunting lodge." 
 
Restatement (Third) § 27 comment a, illustration 1. 
31 
 
which is in operation at the time the plaintiff's harm occurs, 
the factual causation requirement is satisfied."  See 
Restatement (Third) § 27 comment a.  In such cases, where there 
are multiple, simultaneously operating, sufficient causes, the 
jury do not have to make a but-for causation finding.  This 
approach avoids the confusing terminology presented by the terms 
"substantial factor" or "substantial contributing factor."  It 
also eliminates the risk of the judge instructing the jury on 
the wrong standard, as this instruction supplements the but-for 
standard without conflicting with it.23 
We recognize that the substantial factor test is a familiar 
standard in Massachusetts and that it has been used in the past, 
arguably with our endorsement, albeit for specific purposes.  
                    
 
23 The concurrence reads our opinion as providing "not one 
standard of factual causation but many," including "basic but 
for," "but for plus", and "the new instruction on [multiple 
sufficient cause] cases."  Post at    .  This is incorrect. See 
parts 2.a.i.C and 2.a.i.D, supra ("in the majority of negligence 
cases, the jury should be instructed on factual cause using a 
but-for standard"; "in the rare cases presenting the problem of 
multiple sufficient causes, the jury should receive additional 
instructions on factual causation" [emphases added]).  There is 
no "but-for plus"; we merely make clear what nearly every other 
jurisdiction recognizes -- that there is no requirement that a 
defendant be the sole factual cause of the harm.  See Reporter's 
Note to Restatement (Third) § 26 comment c.  With the exception 
of toxic tort cases, see note 21, supra, and the exceedingly 
rare multiple sufficient cause cases, the but-for standard will 
be the standard for factual causation.  The other instructions 
we provide today merely clarify or expand on that concept in 
appropriate cases. 
32 
 
See, e.g., Matsuyama, 452 Mass. at 30-31.  That we have used 
this standard before, however, does not automatically mean that 
we should continue to do so.  In fact, given that the 
Restatements are the source of this standard,24 the Restatement 
(Third)'s own recent criticism and rejection of this standard 
based on its confusing application provide good reason to 
reconsider its use.  Having thoroughly considered these 
standards now, we conclude that the substantial contributing 
factor test should no longer be used in most negligence cases. 
 
ii.  Jury instructions on standard of care and breach.  
Next, the plaintiffs claim that the jury instructions improperly 
emphasized reliance on expert testimony for establishing the 
standard of care and breach regarding informed consent, citing 
to the following portions of the jury instructions as 
problematic: 
"In determining the -- the standard of care that applied at 
the time Nurse Practitioner Foster and Dr. Miller treated 
Laura Doull you must -- you must consider the testimony of 
the witnesses who offered their expert opinions on the 
applicable standard of care.  That is, Dr. Genecin, Dr. 
Hill, Dr. Kenneth Miller and Dr. Potter.  You do not decide 
on your own what the standard of care is or should have 
been, what it ought to have been.  You must decide the 
standard of care based on the testimony of those witnesses.  
And obviously, as I said earlier, if there's conflict 
between the -- their opinions as to what the standard of 
                    
 
 
24 Early Massachusetts cases using a substantial factor 
standard relied on the first Restatement.  See, e.g., Quinby, 
318 Mass. at 444; Vigneault, 300 Mass. at 229; McKenna v. 
Andreassi, 292 Mass. 213, 218 (1935).  We also relied on the 
Restatement (Second) in O'Connor, 401 Mass. at 592. 
33 
 
care is, your role is to determine which opinion you credit 
in that regard. 
 
"You may also consider, and should also consider, any 
medical resources that may have been available to Dr. 
Miller and to Nurse Practitioner Foster during the time 
period that they were treating Laura Doull as one aspect of 
the skill and care required of them at the time. . . .  You 
make that determination [of the standard of care] from all 
of the evidence introduced during the trial as well as, as 
I said, you must take into account the -- the testimony of 
the four medical experts and their testimony with regard to 
what the standard of care was." 
 
 
The plaintiffs contend that the trial judge was required to 
instruct the jury that the standard of care could come from 
regulations, specifically 244 Code Mass. Regs. § 9.04(5) 
(2000),25 and that breach could be established through an 
admission of fault.  The plaintiffs conclude that the judge's 
failure to instruct on these points led the jury to find that 
the defendants had acquired Doull's informed consent regarding 
the progesterone cream.  Because the plaintiffs objected, we 
review for prejudicial error.  See Blackstone v. Cashman, 448 
Mass. 255, 270 (2007).  We conclude that the judge's 
instructions were not erroneous. 
                    
 
 
25 Title 244 Code Mass. Regs. § 9.04(5) states:  "Full 
Disclosure.  When proposing any diagnostic or therapeutic 
intervention which is beyond the scope of generic nursing 
practice, an [advanced practice nurse] shall fully disclose to 
the patient or to the patient's representative the risks and 
benefits of, and alternatives to, such intervention and shall 
document such disclosure in the patient's record." 
34 
 
 
A.  Standard of care.  "To prevail on a claim of medical 
malpractice, a plaintiff must establish the applicable standard 
of care . . . ."  Palandjian v. Foster, 446 Mass. 100, 104 
(2006).  "In Massachusetts, 'it is entirely proper to offer in 
evidence . . . [an official regulation] to show the relevant 
standard of care.'"  Campbell v. Cape & Islands Healthcare 
Servs., Inc., 81 Mass. App. Ct. 252, 255 (2012), quoting Herson 
v. New Boston Garden Corp., 40 Mass. App. Ct. 779, 793 (1996).  
See Mass. G. Evid. § 414 (2020) ("Safety rules, governmental 
regulations or ordinances, and industry standards may be offered 
by either party in civil cases as evidence of the appropriate 
care under the circumstances").  However, a judge need not 
instruct on a regulation if it is "not relevant to the facts of 
[the] case."  Boothby v. Texon, Inc., 414 Mass. 468, 483, 484 
(1993) ("A judge need not instruct the jury on every spin that a 
party can put on the facts"). 
 
Focusing on what was disputed here regarding the informed 
consent claims resolves the plaintiffs' issue with the adequacy 
of the standard of care instructions.  At trial, it was 
undisputed that the defendants owed Doull a duty to inform her 
about the material risks of, and alternatives to, the 
35 
 
progesterone cream.26  The parties disputed what constituted a 
material risk of the treatment, with each side putting forth 
conflicting expert testimony on whether natural progesterone 
cream applied topically would increase the chances of developing 
blood clots.  It is unclear how further instruction on 244 Code 
Mass. Regs. § 9.04(5), which speaks only generally of the duty 
to inform, could have aided the jury in establishing the 
progesterone cream's material risks.27  To establish these, 
jurors would have had to look to expert testimony -- exactly 
what the judge instructed them to do.  Therefore, the standard 
of care instructions did not prejudice the plaintiffs. 
 
B.  Breach.  The plaintiffs' argument that the trial judge 
erroneously failed to instruct the jury that breach could be 
established through a defendant's admission is equally without 
                    
 
 
26 In fact, the judge instructed the jury that "a medical 
care provider owes to his or her patient the duty to disclose, 
in a reasonable manner, all significant medical information that 
the medical care provider possesses or reasonably should 
possess[] that is material to an intelligent decision by the 
patient whether to undergo a proposed course of treatment." 
 
 
27 The plaintiffs also, somewhat obliquely, point to other 
policies and procedures offered in evidence as sources of the 
standard of care, alleging that these, too, were improperly 
overshadowed by expert testimony in the instruction.  Because 
the judge told the jurors to examine all of the evidence entered 
during the trial when determining the standard of care, it is 
unclear how the instructions were improper, let alone 
prejudicial. 
36 
 
merit.28  "Testimony concerning conclusory admissions by a 
malpractice defendant may suffice to sustain a jury's finding of 
negligence if, from the admission, the jury 'could infer an 
acknowledgment of all the necessary elements of legal 
liability.'"  Collins v. Baron, 392 Mass. 565, 568 (1984), 
quoting Zimmerman v. Litvich, 297 Mass. 91, 94 (1937).  Indeed, 
we have said that "a doctor's admission that an injury was 'his 
fault' sufficed to warrant a jury's finding of negligence.  See 
Collins, supra, citing Tully v. Mandell, 269 Mass. 307, 308-309 
(1929).  No such admission, however, is at issue here. 
 
During her testimony at trial, Foster admitted that she did 
not inform Doull that natural progesterone cream carried any 
risk of blood clotting.  Yet, this admission would not have been 
sufficient to render Foster liable for failing to acquire 
informed consent from Doull:  the jury would have had to find 
that natural progesterone cream carried a risk of causing blood 
clots in order for Foster to have committed a breach of her duty 
to inform Doull about the risk.  Cf. Collins, 392 Mass. at 566 
(defendant admitted that he "made a mistake during the 
                    
 
 
28 The plaintiffs' argument on this point is difficult to 
follow.  They claim that the "erroneous instruction also spread 
to the breach portion of the case, again with overemphasis on 
experts."  This is followed by discussion of Foster's admission 
discussed infra.  Consequently, we interpret this argument as a 
claim that the judge ought to have instructed the jury that 
Foster's admissions could establish breach. 
37 
 
hysterectomy," had severed plaintiff's ureter, and was at 
fault).  Whether the progesterone cream posed such a risk was a 
matter that the jury would have had to turn to the experts' 
testimony to determine.  The jury instructions on breach, then, 
were proper. 
 
b.  Motion to amend.  The plaintiffs contend that their 
motion to amend the complaint to add WIC as a defendant should 
have been allowed.  The judge denied the plaintiffs' motion on 
the grounds that the discovery deadline had passed and the 
plaintiffs had failed to explain why they had not added WIC 
earlier. 
 
"We review the denial of a motion to amend the complaint 
for abuse of discretion."  Dzung Duy Nguyen v. Massachusetts 
Inst. of Tech., 479 Mass. 436, 461 (2018).  Despite this 
standard, "leave should be granted unless there are good reasons 
for denying the motion."  Mathis v. Massachusetts Elec. Co., 409 
Mass. 256, 264 (1991).  See Mass. R. Civ. P. 15 (a), 365 Mass. 
761 (1974).  "Such reasons include 'undue delay, bad faith or 
dilatory motive on the part of the movant, repeated failure to 
cure deficiencies by amendments previously allowed, undue 
prejudice to the opposing party by virtue of allowance of the 
amendment, [and] futility of the amendment . . . .'"  Mathis, 
supra, quoting Castellucci v. United States Fid. & Guar. Co., 
372 Mass. 288, 290 (1977). 
38 
 
 
The plaintiffs claim to have learned in November 2016 that 
the defendants had ordered from WIC the progesterone cream that 
Foster prescribed to Doull.  The plaintiffs did not move to add 
WIC as a party until April 2017, approximately five months after 
making the discovery and four months before trial began.  At the 
time of their motion, the plaintiffs failed to explain the delay 
or address that the discovery period had expired.  Given these 
facts, the judge's denial of the plaintiffs' motion was not an 
abuse of discretion.  See Mathis, 409 Mass. at 264-265 ("an 
unexcused delay in seeking to amend is a valid basis for denial 
of a motion to amend"); Castellucci, 372 Mass. at 292 ("When 
trial is as imminent as it was in this case, a judge may give 
weight to the public interest in the efficient operation of the 
trial list and to the interests of other parties who are ready 
for trial"). 
 
c.  Posttrial contact with jurors.  The plaintiffs argue 
that the trial judge improperly granted the defendants' motion 
to require judicial approval for postverdict contact with the 
jurors.  Considering the reasons for the plaintiffs' request to 
initiate contact with the jurors, the judge's decision was 
proper. 
 
Attorneys are generally not required to seek court approval 
before initiating postverdict contact with the jury.  See 
Commonwealth v. Moore, 474 Mass. 541, 551 (2016).  An attorney 
39 
 
may not, however, initiate postverdict contact with the jury if 
"the communication is prohibited by law or court order" 
(emphasis added).  Mass. R. Prof. C. 3.5 (c) (1), as appearing 
in 471 Mass. 1428 (2015).  See Moore, supra at 549 n.10 ("We do 
not question that, when appropriate, a judge in a particular 
case may restrict or even prohibit attorneys' unsupervised 
communication with jurors postverdict; such a court order is 
expressly contemplated by rule 3.5 [c] [1]").  A judge may bar 
postverdict contact with the jury if the attorney seeks to 
inquire "into the contents of jury deliberations and thought 
processes of jurors."  Id. at 548. 
 
In response to the defendants' motion to require judicial 
approval for postverdict contact with the jurors, the plaintiffs 
explained that they sought to contact the jurors in order to ask 
them "how they felt about [Miller's trial counsel] nearly 
assaulting Dr. Genecin . . . on the witness stand and if they 
would have felt differently if the attorney was male and witness 
was female."29  These objectives fall far afield of anything 
resembling a valid reason for approaching jurors and instead 
appear to be aimed at "inquiry into the contents of jury 
deliberations and thought processes of jurors and the 
                    
 
 
29 In granting the defendants' motion, the trial judge noted 
that no assault occurred and that the plaintiffs' suggestion 
otherwise could distort the jurors' understanding of the 
advocacy process. 
40 
 
impeachment of jury verdicts based on information that might be 
gained from such inquiry."  See Moore, 474 Mass. at 548.  For 
these reasons, the trial judge's concerns that the plaintiffs 
would pry into the jurors' deliberations were warranted and the 
prohibition on postverdict contact with the jury was 
appropriate. 
 
d.  Additional claims.  Finally, the plaintiffs make a 
litany of arguments that cite few or no legal authorities, 
contain cursory or no argumentation, or are unsubstantiated in 
the record or reference no portions of the record at all.30  
                    
 
 
30 The plaintiffs contend, for example, that if the trial 
judge had admitted every publication they offered in evidence, 
then "a different result on the informed consent questions would 
have been likely."  For this conclusion, the plaintiffs cite 
once to Pfeiffer v. Salas, 360 Mass. 93, 99 (1971), but provide 
no discussion of it.  We further discern no abuse of discretion 
in the trial judge's limitations on the use and reference to 
certain drugs containing progesterone that were not demonstrated 
to be the same as or sufficiently similar to the topical 
progesterone cream used by Doull.  Next, the plaintiffs make at 
least nine different versions of the argument that the judge 
systematically abused her discretion and deprived them of a fair 
and balanced trial.  For each iteration of this claim, the 
plaintiffs fail to explain how the judge abused her discretion 
or how it prejudiced them, resorting instead to vague 
declarations that they were denied a fair trial.  The plaintiffs 
then turn to the judge's denial of their motion for judgment 
notwithstanding the verdict on the defendants' affirmative 
defenses.  For this claim, the plaintiffs make no argument on 
appeal at all, instead directing our attention to arguments they 
made below.  Finally, the plaintiffs argue that the judge abused 
her discretion in various ways during the pretrial and discovery 
processes.  Again, these claims are made with scant argument.  
More is required from appellate advocates. 
2 
 
These claims do not rise to the level of appellate argument.31  
See Mass. R. A. P. 16 (a) (9), as amended, 428 Mass. 1603 
(1999).  We therefore do not consider them.32 
 
3.  Conclusion.  For the foregoing reasons, we affirm the 
judgment and the order denying the plaintiffs' motion for a new 
trial. 
 
 
 
 
 
 
 
So ordered. 
                    
 
 
31 Because the plaintiffs' appeal raised nonfrivolous 
issues, we reject the defendants' call to award appellate 
attorney's fees and double costs.  See Masterpiece Kitchen & 
Bath, Inc. v. Gordon, 425 Mass. 325, 330 n.11 (1997) ("The 
determination whether an appeal is frivolous is left to the 
sound discretion of the appellate court . . .").  See also Avery 
v. Steele, 414 Mass. 450, 455 (1993), quoting Allen v. 
Batchelder, 17 Mass. App. Ct. 453, 458 (1984) ("An appeal is 
frivolous '[w]hen the law is well settled, when there can be no 
reasonable expectation of a reversal'"). 
 
 
32 We cannot, however, pass over in silence the many 
references made in the plaintiffs' brief to the trial judge's 
supposed biases.  At various points, the plaintiffs' counsel 
insinuates or outright alleges that the trial judge was biased 
toward the defendants.  Indeed, the plaintiffs' brief concludes 
by noting of the causation issue:  "The simple truth is the 
Trial Court gave the wrong instruction of law in order to 
guarantee a defense verdict."  We have reviewed the transcript, 
and the judge exhibited patience, rectitude, and fairness 
throughout the trial.  The record supports none of the 
accusations found in the plaintiffs' briefs. 
 
LOWY, J. (concurring, with whom Gaziano, J., joins).  Today 
the court abandons decades of precedent in an attempt to clarify 
confusion that does not exist.  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.  To be 
clear, I agree that regardless of the test, the outcome in this 
case is the same.  Here, the jury found only one breach on which 
to consider causation; this is the paradigmatic situation for 
but-for causation.1  Yet for the following reasons, I would 
maintain the current practice of applying the substantial 
contributing factor test to multiple cause cases. 
 
1.  Current law.  We have long applied the substantial 
contributing factor test.  See, e.g., Bernier v. Boston Edison 
Co., 380 Mass. 372, 386 (1980); Tritsch v. Boston Edison Co., 
                    
 
 
1 At trial, plaintiffs argued three theories of negligence:  
(1) that Anna C. Foster and Richard J. Miller failed to acquire 
informed consent from Laura Doull, (2) that Foster failed to 
diagnose Doull properly during her spring 2011 visits, and (3) 
that Miller was negligent in his supervision of Foster.  The 
jury eliminated informed consent as a possible theory, thus 
leaving only the failure to diagnose and the negligent 
supervision claims.  These two theories of negligence shared 
only one cause, because finding liability on the negligent 
supervision claim hinged on the failure to diagnose claim.  
Thus, although the judge should have initially instructed on the 
substantial contributing factor test, failure to do so was 
harmless. 
2 
 
363 Mass. 179, 182 (1973); Falvey v. Hamelburg, 347 Mass. 430, 
435 (1964); Quinby v. Boston & Me. R.R., 318 Mass. 438, 444-445 
(1945); Vigneault v. Dr. Hewson Dental Co., 300 Mass. 223, 229 
(1938).  References in our cases to causes being "substantial 
contributing" factors even predate the test's modern formulation 
in the Restatement of Torts (1939) and Restatement (Second) of 
Torts (1965).  See Wheeler v. Worcester, 10 Allen 591, 594, 597 
(1865).  In recent years, we have refined how the test is 
applied to cause-in-fact problems.  See Matsuyama v. Birnbaum, 
452 Mass. 1, 30-31 (2008) (limiting substantial contributing 
factor test to cases with multiple causes).  Examination of the 
test reveals why it has so long endured. 
 
To begin, note how the substantial contributing factor test 
mirrors the analysis of but-for causation.  Save for the rare 
instances where two or more causes are each alone sufficient to 
produce a result, we have made clear that a substantial 
contributing factor must actually make a difference as to 
whether an event occurs in order to be considered a cause of it.  
In O'Connor v. Raymark Indus., Inc., 401 Mass. 586, 592 (1988), 
for example, we held that a jury must "distinguish between a 
'substantial factor,' tending along with other factors to 
produce the plaintiff's [harm], and a negligible factor, so 
slight or so tangential to the harm caused that, even when 
combined with other factors, it could not reasonably be said to 
3 
 
have contributed to the result."  If the plaintiff cannot 
demonstrate that the defendant's negligence substantially 
contributed to the alleged harm, then the defendant cannot be 
held liable.  See id. at 587.  Just as but-for causation does, 
the substantial contributing factor test embodies a core 
principle of tort law:  only those who meaningfully contributed 
to a person's harm should be liable for it.2  See Wainwright v. 
Jackson, 291 Mass. 100, 102 (1935). 
                    
 
 
2 Semantics further proves the point.  A substantial 
contributing factor must first and foremost be a genuine factor.  
It would be difficult to contemplate how conduct could 
"substantially" contribute to an outcome and yet the outcome 
would have happened without the conduct.  See Black's Law 
Dictionary 1728 (11th ed. 2019) (defining "substantial" as "1.  
Of, relating to, or involving substance; material . . . .  2.  
Real and not imaginary; having actual, not fictitious, existence 
. . . .  3.  Important, essential, and material; of real worth 
and importance"). 
 
 
Other courts have echoed this sentiment.  See, e.g., June 
v. Union Carbide Corp., 577 F.3d 1234, 1239 (10th Cir. 2009) 
("the ultimate legal standards in the two Restatements," one of 
which advocates substantial contributing factor and other of 
which advocates but-for cause, "are essentially identical"); 
Mitchell v. Gonzales, 54 Cal. 3d 1041, 1052 (1991) ("the 
'substantial factor' test subsumes the 'but for' test"); 
Burnette v. Eubanks, 308 Kan. 838, 850-851 (2018) ("An act of 
negligence which contributes to an accident must, of necessity, 
have at least a part in causing the accident" [citation 
omitted]).  Hence, even critics of the substantial contributing 
factor test concede that it works fine when clearly delineated:  
the test implicitly subsumes within it the same requirements of 
but-for cause.  See Robertson, The Common Sense of Cause in 
Fact, 75 Tex. L. Rev. 1765, 1781 (1997) ("As long as courts are 
careful to explain that they are not adding a sixth requirement 
-- but instead are either using the 'substantial factor' test 
for cause in fact in lieu of the but-for approach or are using 
4 
 
 
Where the two tests part ways is in where they focus 
jurors' attention.  The substantial contributing factor test is 
positive in outlook:  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.  See 
Restatement (Second) of Torts § 431(a).  But-for causation, on 
the other hand, begins not with what was, but with what might 
have been:  in order to determine whether what occurred was the 
product of the defendant's action, the jury must determine how 
the sequence of events would have played out in the absence of 
this conduct.  See Restatement (Third) of Torts:  Liability for 
Physical and Emotional Harm § 26 comment e (2010) (Restatement 
[Third] of Torts). 
 
Although this counterfactual framing may be straightforward 
when the jury are considering only one theory of causation, I 
fear that in cases with multiple causes it invites the jury to 
get caught up in speculative combinations of "what if" and "if 
only."  See, e.g., Green, The Causal Relation Issue in 
Negligence Law, 60 Mich. L. Rev. 543, 556 (1962) ("Tests of this 
character have the same vice as any 'if,' or any analogy.  They 
take the eye off the ball").  See also Spellman & Kincannon, The 
Relation Between Counterfactual ("But For") and Causal 
                    
 
the 'substantial factor' vocabulary to describe a general 
approach to the legal cause issue -- no clear harm is done"). 
5 
 
Reasoning:  Experimental Findings and Implications for Jurors' 
Decisions, 64 Law & Contemp. Probs. 241, 243-247 (2001) 
(detailing how moral and other nonfactual factors enter into 
jurors' considerations when engaged in counterfactual 
reasoning).  The substantial contributing factor test better 
replicates how many people understand causation and thus avoids 
this issue. 
 
These considerations reveal not only why we recently said 
that the substantial contributing cause test was "useful" in 
cases with multiple causes, but also how the test promotes 
fairness.  Matsuyama, 452 Mass. at 30.  As with the other 
elements of a negligence claim, plaintiffs bear the burden of 
proving causation.  See Glidden v. Maglio, 430 Mass. 694, 696 
(2000).  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.  For 
example, civil defendants in cases with multiple causes 
sometimes "employ an 'empty chair' defense -- blaming the party 
not on trial."  Lind v. Domino's Pizza LLC, 87 Mass. App. Ct. 
650, 665 (2015).  This strategy is but one example of how but-
for causation encourages jurors to speculate about alternative 
realities.  An instruction on the substantial contributing 
factor test, however, focuses the jurors attention directly on 
6 
 
what ought to determine legal responsibility:  the conduct of 
the parties. 
 
2.  The court's approach.  The court abandons what has been 
our steady and successful practice of applying the substantial 
contributing factor test in torts cases involving all sorts of 
fact patterns, not just in "twin fire" and toxic tort cases.  
See, e.g., Renzi v. Paredes, 452 Mass. 38, 44 n.10 (2008) 
(substantial contributing factor test proper in loss of chance 
case where liability was premised on failure to diagnose); Morea 
v. Cosco, Inc., 422 Mass. 601, 603 n.2 (1996) (jury found 
defective product design not "substantial cause" of child's 
death); Michnik-Zilberman v. Gordon's Liquor, Inc., 390 Mass. 6, 
14 (1983) (jury could find liquor store's sale of alcohol to 
minor was "substantial legal factor" causing cyclist's death); 
Mullins v. Pine Manor College, 389 Mass. 47, 58, 62 (1983) (jury 
could find that injury to rape victim was substantially caused 
by college's negligent security). 
 
Why the sudden about-face?  Precedent does not dictate the 
new direction, as recent affirmations of the substantial 
contributing factor test attest.  See, e.g., Renzi, 452 Mass. at 
44 n.10.  Practices, too, remain unaltered.  See, e.g., Parsons 
v. Ameri, 97 Mass. App. Ct. 96, 102 (2020) (jury instructed on 
substantial contributing factor test in medical malpractice 
case).  Indeed, even the current Massachusetts Continuing Legal 
7 
 
Education Civil Practice Jury Instructions recognize our use of 
the substantial contributing factor test in cases with multiple 
causes.  See Massachusetts Superior Court Civil Practice Jury 
Instructions § 4.3.4(a) practice note (3d ed. 2014) (but-for 
test is "suitable for use in the ordinary tort case without the 
complexity of multiple causes or tortfeasors"). 
 
Only one thing has changed:  the Restatements.  Whereas 
earlier Restatements embraced the substantial contributing 
factor test, the Restatement (Third) of Torts has rejected it.  
Compare Restatement of Torts § 431(a) and Restatement (Second) 
of Torts § 431(a), with Restatement (Third) of Torts § 26.  
Specifically, the Restatement (Third) calls the substantial 
contributing factor test "confusing," concluding that, aside 
from multiple sufficient cause cases, the test "provides nothing 
of use in determining whether factual cause exists."  
Restatement (Third) of Torts § 26 comment j.  This position is 
now the court's.  What we very recently called "useful" is now 
supposedly no longer so.  See Matsuyama, 452 Mass. at 30. 
 
Of course, we are not bound to follow old law when new 
facts reveal that application is unworkable in our jurisdiction.  
See Franklin v. Albert, 381 Mass. 611, 617 (1980).  Yet such 
facts are absent here.  Notably, when the court discusses the 
confusion that the substantial contributing factor test has 
8 
 
allegedly generated, citations to our cases drop off.3  Instead, 
the court replicates an abstract and academic discussion of the 
problems that the Restatement (Third) of Torts found with the 
standard.4  See ante at    -   .  We should be "disinclined to 
fix something that is not broken, even if [we] would have 
constructed it differently in the first place."5  Stonehill 
College v. Massachusetts Comm'n Against Discrimination, 441 
Mass. 549, 589 (Sosman, J., concurring), cert. denied sub nom. 
Wilfert Bros. Realty Co. v. Massachusetts Comm'n Against 
Discrimination, 543 U.S. 979 (2004). 
 
Furthermore, how much of the apparent confusion the court's 
solution would dispel is unclear.  Although the court criticizes 
the substantial contributing factor test for requiring judges to 
                    
 
 
3 One of the court's citations to our cases is also 
inaccurate.  Matsuyama, 452 Mass. at 30, is a loss of chance 
medical malpractice case; it is neither a toxic tort nor an 
asbestos case, although the court lumps it in with those cases. 
 
 
4 By way of explanation, the Restatement (Third) of Torts 
catalogues various uses of the test across different 
jurisdictions.  The test appears to be more confusing when 
comparing cases across jurisdictions -- which unsurprisingly 
evince the sort of pluralism characteristic of the common law's 
development -- than when comparing cases within a jurisdiction.  
Regardless, absent from these comparisons is Massachusetts.  See 
Restatement (Third) of Torts § 26 comment j. 
 
 
5 Other States have also successfully continued to apply the 
substantial contributing factor test in recent years despite the 
alternative presented by the Restatement (Third) of Torts.  See, 
e.g., O'Grady v. State, 140 Haw. 36, 46 (2017) (reaffirming use 
of test in negligence cases). 
9 
 
determine how many causes are alleged in a case, the court 
provides not one standard of factual causation but many.  First, 
there is basic but-for:  as is currently the practice, in cases 
where there is one alleged cause, jurors should be instructed on 
but-for causation.  See ante at    -   .  Second, there is but-
for plus:  in cases where there are more than one alleged cause, 
it is "appropriate" to also inform the jurors that there can be 
more than one but-for cause of a harm.6  See id. at note 12.  
Third, there is the new instruction on the twin fires example:  
in cases where there are multiple sufficient causes, jurors are 
to be given a hypothetical scenario detailing a camping trip 
gone wrong, told that "[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" along with a follow-up explanation of this instruction, 
and then sent to deliberate.  See id. at    .  Fourth, and 
finally, the substantial contributing factor test remains:  for 
all its purported confusion, the standard continues to work well 
in toxic tort cases -- except for the fact that the court also 
                    
 
 
6 Even but-for plus presents an option within an option, as 
the court implies by noting that it is merely "appropriate," not 
necessary, for the trial judge to so instruct the jury in cases 
where there are multiple alleged causes. 
10 
 
invites in a footnote overturning what it otherwise praises.7  
See id. at note 21. 
 
The Restatements are owed respect.  Our cases, however, 
deserve more.  See Mabardy v. McHugh, 202 Mass. 148, 152 (1909) 
("Parties should not be encouraged to seek re-examination of 
determined principles and speculate on a fluctuation of the law 
with every change in the expounders of it").  The number of 
tests the court provides is a tacit recognition of what our 
cases have long understood:  the but-for standard is useful, but 
limited in its usefulness.  Given that our cases have had 
decades to refine this point, following them is the prudent 
course. 
                    
 
 
7 Additionally, adopting 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.  
See, e.g., HipSaver, Inc. v. Kiel, 464 Mass. 517, 537 (2013), 
quoting Restatement (Second) of Torts § 633 comment g ("[w]hen 
the loss of a specific sale is relied on to establish pecuniary 
loss, it must be proved that the publication was a substantial 
factor influencing the specific, identified purchaser in his 
decision not to buy"); Murphy v. Boston Herald, Inc., 449 Mass. 
42, 67 (2007) ("The judge properly instructed the jury:  'The 
pain and suffering for which [the plaintiff] is entitled to 
recover in this action is the pain and suffering which the 
defamatory statement was, or were, a substantial factor in 
producing'" [alteration in original]); Reisman v. KPMG Peat 
Marwick LLP, 57 Mass. App. Ct. 100, 112 (2003) ("It has long 
been the law in Massachusetts that, where reliance on a 
fraudulent misstatement is a substantial factor in the decision 
to purchase and/or retain stock, the maker of a false 
representation is liable for a subsequent loss in the value of 
stock suffered in reliance on the false representation"). 
11 
 
 
3.  Conclusion.  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.