Criminal Responsibility in Massachusetts Criminal Cases

Lack of criminal responsibility is the Massachusetts defense commonly called the insanity defense. It applies where, at the time of the offense, a mental disease or defect left the defendant without substantial capacity either to appreciate the wrongfulness of the conduct or to conform the conduct to the requirements of law. Commonwealth v. McHoul, 352 Mass. 544, 546 to 547 (1967). A defendant who meets that standard is not guilty, even where the act is proved. The verdict is not guilty by reason of lack of criminal responsibility, an acquittal ordinarily followed by civil commitment rather than release.

The defendant raises the defense, and the Commonwealth carries the burden of disproving it. Once the evidence, viewed in the light most favorable to the defendant, would permit a reasonable doubt about criminal responsibility, the Commonwealth must prove beyond a reasonable doubt that the defendant was criminally responsible. Commonwealth v. Keita, 429 Mass. 843, 849 to 850 (1999); Commonwealth v. Lawson, 475 Mass. 806, 814 (2016). The Commonwealth may meet that burden with expert testimony, with evidence of what the defendant did before, during, and after the offense, or with both.

The McHoul Standard

The standard has four elements. The defendant must have had a mental disease or defect. It must have existed at the time of the conduct charged. Because of it, the defendant must have lacked substantial capacity. And the incapacity must concern either the ability to appreciate the wrongfulness or criminality of the conduct or the ability to conform the conduct to the requirements of law.

Either incapacity is enough. A defendant who knew the act was wrong but could not refrain from it is not criminally responsible, and neither is a defendant who could have controlled the conduct but could not appreciate that it was wrong. The two branches are put to the jury as alternatives, and the Commonwealth must disprove both.

Substantial capacity does not mean total incapacity. McHoul adopted the Model Penal Code formulation in place of the older Massachusetts rule, which had asked whether the defendant knew right from wrong. The word substantial was chosen so that a defendant who retained some capacity, but not enough to matter, would still qualify. The word appreciate was chosen in place of know for a similar reason. A defendant may know, in a narrow sense, that an act is against the law while lacking any real capacity to understand its wrongfulness.

Criminality and wrongfulness are different things. Criminality means knowledge that the act was against the law. Wrongfulness means an understanding that the act was morally wrong. The Commonwealth satisfies this part of the standard by proving that the defendant had substantial capacity to appreciate either one, and it need not prove both. Commonwealth v. Rezac, 494 Mass. 368, 371 (2024). The model instruction judges use, which the Supreme Judicial Court set out in an appendix to Commonwealth v. Goudreau, 422 Mass. 731, 737 to 738 (1996), and which the Model Jury Instructions on Homicide (2018) carry forward, puts the question to the jury in those terms.

The inquiry is fixed at the moment of the conduct. A defendant may have been ill for years before the offense and may be ill at trial, and neither fact answers the question. What matters is whether, when the act was committed, the illness had deprived the defendant of substantial capacity. Mental illness alone does not establish lack of criminal responsibility, and juries are instructed accordingly. Commonwealth v. Loya, 484 Mass. 98 (2020).

The question is also asked charge by charge. Where a defendant faces several charges arising from separate acts, the jury may find the defendant not criminally responsible for one and guilty of the others, if the evidence supports a different answer for different moments. Commonwealth v. McLaughlin, 431 Mass. 506, 508 (2000).

What Counts as a Mental Disease or Defect

Mental disease or defect is a legal term, not a medical one. The jury decides whether the defendant’s condition qualifies, and it is not bound by the diagnostic categories of any manual or by an expert’s definition. Commonwealth v. Sheehan, 376 Mass. 765 (1978); Commonwealth v. Laliberty, 373 Mass. 238, 241 to 242 (1977). An expert who testifies for either side must address the McHoul standard itself, not only the diagnosis. A diagnosis is the beginning of the analysis, not the end of it.

Some conditions are excluded. McHoul adopted the Model Penal Code’s exclusion of an abnormality manifested only by repeated criminal or otherwise antisocial conduct, so a history of offending is not itself a mental disease. Drug addiction, standing alone, is not a mental disease or defect. Commonwealth v. Sheehan, 376 Mass. 765 (1978). The interaction between mental illness and intoxication is addressed in a later section.

The conditions that most often support the defense are psychotic disorders: schizophrenia, schizoaffective disorder, bipolar disorder with psychotic features, major depressive disorder with psychotic features, and delusional disorder. Intellectual disability, dementia, and traumatic brain injury are mental defects rather than diseases and are analyzed the same way. Whether a personality disorder qualifies is usually disputed, because the Commonwealth ordinarily argues that a personality disorder explains conduct without impairing capacity.

Postpartum Illness as a Mental Disease

No Massachusetts statute or decision creates a separate defense for postpartum illness. The question is the McHoul question: whether the condition was a mental disease and whether, at the time of the act, it deprived the defendant of substantial capacity. Postpartum illness is evaluated under that standard like any other condition, and the answer depends on the medical evidence in the particular case.

The conditions range from postpartum depression, which is common and is usually treated without hospitalization, to postpartum psychosis, which is rare, typically begins within the first weeks after childbirth, and can include delusions, hallucinations, disorganized thinking, and thoughts of harming the infant. Postpartum psychosis is a medical emergency, and it is associated with bipolar disorder and with a prior psychiatric history. A depression with psychotic features falls between the two. The experts are asked which condition the defendant had and how far it had progressed on the day in question.

The evidence in these cases is largely documentary. Prenatal and postpartum medical records, the notes of treating clinicians, prescriptions and dosage changes, messages to providers, family, and friends, and the observations of the people who saw the mother in the days before the offense are the material from which both experts work.

In Commonwealth v. Sanders, SJC-13552 (Aug. 6, 2026), the Supreme Judicial Court vacated the convictions of a mother who had killed her two children because medical records made after her arrest, which documented her mental illness, had been excluded. The records were admissible under G.L. c. 233, § 79.

The evidence of illness matters even where the jury rejects the defense. In Commonwealth v. Colleran, 452 Mass. 417, 432 to 434 (2008), a mother with profound psychotic depression was convicted of murder in the first degree, and the Supreme Judicial Court reduced the verdict to murder in the second degree under G.L. c. 278, § 33E because of the weight of that evidence. That remedy exists only in first-degree murder cases, and it is discussed below.

The Commonwealth’s response to postpartum evidence follows a pattern. Depression after childbirth is common, so the Commonwealth argues that the defendant’s condition was the common kind and not the kind that removes capacity. It points to ordinary functioning in the surrounding days: appointments kept, messages sent, children cared for. It asks whether any clinician documented psychosis before the offense rather than after the arrest. It also looks for planning. The defense answers with the records, the course of the illness, the treating clinicians, and the absence of any rational motive.

Raising the Defense

The defense begins with notice. Under Mass. R. Crim. P. 14(b)(2), as appearing in 481 Mass. 1626 (2019), a defendant who intends to rely on lack of criminal responsibility must notify the prosecutor in writing, within the time allowed for pretrial motions or such later time as the judge permits. The notice states whether the defendant intends to offer expert testimony and whether that testimony will rest on the defendant’s own statements. A late notice risks exclusion of the expert.

The court may then order an examination. Under G.L. c. 123, § 15, after a complaint or indictment issues, a judge who has reason to doubt the defendant’s criminal responsibility may order an examination by a qualified physician or psychologist. The examination may take place at the courthouse, or the defendant may be hospitalized for observation for up to 20 days, extendable to 40 days. The examiner reports in writing, with clinical findings, on the defendant’s mental condition at the time of the offense.

A defendant who offers an expert opinion based on the defendant’s own statements to the expert waives, to that extent, the privilege against self-incrimination. The Commonwealth is then entitled to its own examination so that its expert can testify on the same basis. Blaisdell v. Commonwealth, 372 Mass. 753 (1977). Rule 14(b)(2) adopted the Blaisdell procedure.

The examination proceeds under a protective order, and the examiner’s report is sealed until the defendant offers the expert evidence at trial. A defendant who refuses the examination may be barred from presenting expert testimony based on the defendant’s statements.

At trial, the question goes to the jury if the evidence, viewed in the light most favorable to the defendant, would permit a reasonable doubt about criminal responsibility. Commonwealth v. Lawson, 475 Mass. 806 (2016), citing Commonwealth v. Berry, 457 Mass. 602, 612 (2010). The evidence may come from the defense case, from the Commonwealth’s own witnesses, or from the defendant’s testimony, and expert testimony is not required to raise it. Commonwealth v. Mattson, 377 Mass. 638, 644 (1979); Commonwealth v. Monico, 396 Mass. 793, 798 (1986).

In practice the defense is presented through a psychiatrist or psychologist who examined the defendant, reviewed the records, and can testify in the terms McHoul requires. Because the Commonwealth’s burden on this issue arises only after the evidence has raised it, a motion for a required finding of not guilty on the ground that criminal responsibility was not proved is ordinarily made at the close of all the evidence. Commonwealth v. Lawson, 475 Mass. 806 (2016). The Commonwealth is entitled to rebut the defense evidence before the sufficiency of its proof is measured.

The Commonwealth’s Burden

Once the defense is in the case, the Commonwealth must prove criminal responsibility beyond a reasonable doubt. That means proving one of two negatives: that the defendant had no mental disease or defect, or that, if the defendant had one, it did not cause the incapacity the standard describes. Commonwealth v. Keita, 429 Mass. 843, 849 to 850 (1999). The defendant bears no burden of proof on the question. The allocation is the same one that applies to self-defense once that defense is raised.

For many years juries were told of a presumption of sanity. Lawson ended that practice. The presumption is only an inference from the fact that most people are sane, it is not enough by itself to prove criminal responsibility, and judges are directed not to instruct juries about it. Commonwealth v. Lawson, 475 Mass. 806, 814 (2016). The jury may still infer, from the evidence in the case, that the defendant was among the majority. It may not be told to begin from that assumption.

The Commonwealth need not call an expert. It may prove criminal responsibility through the facts of the offense and the defendant’s conduct, and a jury may reject the testimony of a defense expert, even uncontradicted testimony, and infer responsibility from what the defendant did. Commonwealth v. Kappler, 416 Mass. 574, 579 (1993); Commonwealth v. Lunde, 390 Mass. 42, 47 (1983); Commonwealth v. Kostka, 370 Mass. 516, 530 (1976). That rule is the reason these trials are so often decided on the conduct evidence rather than on the diagnosis.

How Prosecutors Attack the Defense

Lawson lists the kinds of evidence from which a jury may infer criminal responsibility, and the list is a description of how these cases are prosecuted. It includes planning before the offense, a motive that makes sense, rational decisions in committing the offense and in avoiding capture, concealment of the act or of the evidence, the defendant’s words and conduct before, during, and after the offense, and malingering, meaning the exaggeration or invention of symptoms. Commonwealth v. Lawson, 475 Mass. 806, 816 (2016).

Each item is developed through ordinary evidence. Planning is shown through purchases, searches, and messages in the days before. Rational motive is argued from the relationship between the defendant and the person harmed. Rational conduct during the offense is shown through the sequence of events and anything the defendant did to avoid interruption. Conduct afterward includes flight, false statements to police, disposal of evidence, and what the defendant first said about it. The Commonwealth’s argument is that a person who did those things understood what was being done and was able to choose.

The defense expert is cross-examined on the foundation of the opinion. The prosecutor asks how much of it rests on what the defendant said in interviews conducted months after the arrest. The prosecutor asks what records the expert did not review, whether any clinician documented the symptoms before the offense, what testing for malingering was done, how often the expert testifies for the defense, and what the expert was paid. None of those questions disproves the illness. Each is meant to give the jury a reason to discount the opinion.

The Commonwealth then calls its own examiner, ordinarily the physician or psychologist who conducted the court-ordered examination. That witness often agrees that the defendant has a diagnosis and disagrees about capacity, testifying that the defendant appreciated the wrongfulness of the conduct or could have conformed to the law despite the illness. Where the Commonwealth’s expert concedes the diagnosis, the trial narrows to the capacity question, and the conduct evidence becomes the decisive material.

The closing argument that follows has a standard form. The defendant was ill, and illness is not the question. The defendant planned, chose, concealed, and lied, and a person who does those things has the capacity the standard requires. Mental illness does not equate with lack of criminal responsibility, and the Commonwealth is entitled to argue the distinction as forcefully as the evidence allows. Commonwealth v. Loya, 484 Mass. 98 (2020).

There are limits, and they are enforced. A prosecutor may not appeal to the jury’s sympathy for the victims. Commonwealth v. Santiago, 425 Mass. 491, 501 (1997). A prosecutor may not attach a pejorative label to the defendant. Commonwealth v. Lewis, 465 Mass. 119, 130 (2013); Commonwealth v. Bois, 476 Mass. 15, 34 to 36 (2016).

A prosecutor may describe the act as evil only in the sense that bears on wrongfulness, and may not argue facts that are not in evidence. Commonwealth v. Sanders, SJC-13552 (Aug. 6, 2026). The rules governing closing argument apply with particular force in a trial where the acts are not disputed and the only question is the defendant’s mind.

Alcohol, Drugs, and Mental Illness

Voluntary intoxication is not a mental disease or defect, and neither is addiction. A defendant whose incapacity resulted from alcohol or drugs alone has no defense under McHoul. The harder cases involve a defendant who had a mental disease and was also using substances, and Commonwealth v. DiPadova, 460 Mass. 424 (2011), supplies the rules for them.

If the mental disease alone caused the lack of substantial capacity, the defense stands, even if the defendant’s substance use made the symptoms worse and even if the defendant knew it would. If the incapacity was caused by the disease and the substances in combination, the defense still stands unless the defendant knew, or had reason to know, that the substances would have that effect. The standard is subjective. The question is what this defendant knew about the effect of these substances on this illness, not what a reasonable person would have known.

The distinction matters because substance use is a frequent feature of these cases and the Commonwealth will argue it. The instruction the jury receives on the point is often contested. A defense that has evidence of the disease’s independent effect should ask for the full DiPadova instruction rather than a general statement that intoxication is no excuse.

Mental Impairment Short of the Defense

A defendant whose illness did not remove substantial capacity may still have a mental impairment that matters. In a murder case, evidence of mental impairment may be considered on whether the defendant deliberately premeditated and on whether the killing was committed with extreme atrocity or cruelty. Commonwealth v. Gould, 380 Mass. 672, 682 (1980); Commonwealth v. Corey, 493 Mass. 674 (2024). The same evidence that supports the defense therefore also supports an argument for a lesser degree of the offense, and the two are ordinarily presented together.

The Supreme Judicial Court also reviews every conviction of murder in the first degree under G.L. c. 278, § 33E and may reduce the verdict where justice requires. Evidence of serious mental illness has produced reductions under that section, as in Colleran, where the court reduced a first-degree conviction to murder in the second degree for a mother with profound psychotic depression. That review is available only in first-degree murder cases. It is a reason the illness evidence is developed fully even where the responsibility verdict is uncertain.

The Bifurcated Trial Question

A bifurcated trial separates the question of whether the defendant committed the offense from the question of criminal responsibility. The jury first decides whether the Commonwealth has proved the elements of the crime. If it has, the same jury hears the psychiatric evidence and decides responsibility. Massachusetts trials are ordinarily unitary, with both questions tried together, and a defendant who wants bifurcation must ask for it.

There is no constitutional right to a bifurcated trial. The decision is committed to the trial judge’s discretion. Commonwealth v. Blanchette, 409 Mass. 99 (1991); Commonwealth v. Siegfriedt, 402 Mass. 424, 431 (1988); Commonwealth v. Bumpus, 362 Mass. 672, 681 (1972). The request is often denied, because the defendant’s state of mind is usually an element of the offense and the same evidence would have to be heard twice.

The defense asks for bifurcation to avoid a particular difficulty. In a unitary trial, the defense may have to contest the facts of the offense and, in the same trial, present expert testimony that assumes the defendant committed it. The jury hears the crime scene evidence and the psychiatric evidence together, and the emotional weight of the first can overwhelm the second. A separate responsibility phase allows the defense to concede the acts, once they have been proved, and to try the only question that is in dispute without the contradiction.

Where bifurcation is denied, the defense has an alternative. A defendant who does not contest the acts can say so at the start, in the opening statement or by stipulation, and put the responsibility question before the jury from the first day. That course carries its own risk, because the concession is binding, and it is chosen only where the acts cannot realistically be disputed. The defense in the Lindsay Clancy case asked for a two-part trial and was refused, and the case was tried to a single jury.

Trial Practicalities

The trial of this defense follows the ordinary rules of Massachusetts criminal court practice, with several features of its own. The first concerns the defendant’s appearance. The jury sees the defendant every day of the trial, and what it sees is a person who is medicated, composed, and attentive. That is the effect of treatment, not evidence of the defendant’s condition on the day of the offense.

A defendant has no absolute right to appear before the jury unmedicated. Commonwealth v. Colleran, 452 Mass. 417 (2008). The defense therefore presents evidence of the medication, its effects on demeanor, and the contrast between the defendant at trial and the defendant described in the records.

On request, the jury is instructed about what follows a verdict of not guilty by reason of lack of criminal responsibility. Commonwealth v. Mutina, 366 Mass. 810 (1975). The instruction explains that the defendant will not simply be released, that the Commonwealth may seek commitment, and that commitment may be renewed for as long as the legal standard is met.

The judge need not state specific time periods, Commonwealth v. Callahan, 380 Mass. 821, 827 to 828 (1980), and may tell the jury that successive commitments can continue for the rest of the defendant’s life. Commonwealth v. Chappell, 473 Mass. 191 (2015). Without the instruction, jurors may assume that the verdict means release.

The verdict is not guilty by reason of lack of criminal responsibility. There is no verdict of guilty but not criminally responsible in Massachusetts, and a verdict slip that suggests one is error. Commonwealth v. Loya, 484 Mass. 98 (2020). Where the case involves several charges, the jury may return that verdict on some and guilty verdicts on others. Commonwealth v. McLaughlin, 431 Mass. 506, 508 (2000). Jury selection in these cases also differs, because prospective jurors may be questioned about their views on mental illness and on the defense itself.

What a Verdict of Not Criminally Responsible Means Afterward

The verdict is an acquittal. There is no conviction, no sentencing, and no probation. The docket records the verdict, and the case ends in the criminal court. What begins is a civil commitment proceeding under G.L. c. 123, § 16, and the district attorney remains a party to it.

Under § 16(a), the court may order the person hospitalized for observation for 40 days. A man who requires strict security may be sent to Bridgewater State Hospital; otherwise the placement is a Department of Mental Health facility. Where the person was already hospitalized for observation before trial under § 15(b), the combined period may not exceed 50 days. The observation period is not a commitment. It is the time in which the facility evaluates the person and decides whether to seek one.

Within 60 days of the verdict, the district attorney, the facility superintendent, or the medical director of Bridgewater State Hospital may petition for commitment. G.L. c. 123, § 16(b). The court commits if it finds, under the standard of § 8, that the person is mentally ill and that discharge would create a likelihood of serious harm. The first commitment is for up to six months. Under § 16(c), further commitments run for one year at a time, with no limit on the number of renewals while the standard continues to be met.

A committed person is a patient, not a prisoner, but the district attorney’s involvement continues. Under § 16(e), restrictions on the person’s movement within the facility grounds may be lifted only with court approval or after 14 days’ notice to the court and the district attorney without objection. A facility that intends to discharge the person must give the same notice, and the district attorney may petition within 30 days to continue the commitment. Release is therefore litigated, and a commitment can outlast the sentence the offense would have carried.

Two consequences follow the commitment rather than the verdict. A person who has been committed to a hospital or institution for mental illness by court order is disqualified from a firearms license under G.L. c. 140, § 121F unless relief is granted under G.L. c. 123, § 36C. A noncitizen should have immigration counsel review the verdict and the commitment record before any application or travel. Because the case ended in an acquittal, the court record may be eligible for sealing under G.L. c. 276, § 100C.

The Clancy Case

The trial of Lindsay Clancy in Plymouth Superior Court presented the defense in the form described above. The acts were not disputed. The defense was lack of criminal responsibility based on postpartum illness and on the psychiatric treatment she had received in the months before. The Commonwealth answered with evidence of planning and of her conduct afterward, including the argument that her own injuries were superficial by design. The defense asked for a bifurcated trial and was refused. The jury reported that it could not agree, and the judge declared a mistrial.

Three pages on this site follow the case. One examines the Commonwealth’s trial tactics, including the decision to argue that her injuries were staged. One addresses the removal of a deliberating juror under G.L. c. 234A, § 39. The rules that govern a mistrial after deadlock, and the retrial that may follow, are set out on the mistrial page.

Talk to a Lawyer About a Criminal Responsibility Defense

Attorney Joe Serpa defends criminal cases in the District Court, the Boston Municipal Court, and the Superior Court. His approach to expert witnesses is described in his own account of how he uses experts. To discuss a case in which criminal responsibility may be a defense, or a family member who has been charged after a psychiatric crisis, contact Serpa Law Office for a free consultation. Related doctrines are collected in the rights and legal concepts section, and case outcomes are collected on the Massachusetts criminal defense results page.

Serpa Law Office can be reached at 617.936.0201.