Criminal Responsibility in Massachusetts Criminal Cases

A defendant in a Massachusetts criminal case may raise the defense of lack of criminal responsibility, commonly called the insanity defense. The defense 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 Commonwealth proves the act. The verdict is not guilty by reason of lack of criminal responsibility. The verdict is an acquittal. A judge ordinarily commits the defendant to a hospital after the verdict instead of releasing the defendant.

The defendant raises the defense. The burden of proof then rests on the Commonwealth. 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. The disease or defect must have existed at the time of the conduct charged. Because of the disease or defect, the defendant must have lacked substantial capacity. 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 establishes the defense. A defendant who knew the act was wrong but could not refrain from the act is not criminally responsible. A defendant who could have controlled the conduct but could not appreciate that the conduct was wrong is also not criminally responsible. The judge instructs the jury on the two branches as alternatives. The Commonwealth must prove beyond a reasonable doubt that the defendant had both capacities.

A defendant need not have lacked all capacity to meet the standard. In McHoul, the Supreme Judicial Court adopted the Model Penal Code formulation in place of the older Massachusetts rule, which had asked whether the defendant knew right from wrong. The court chose the word substantial so that a defendant who retained only a slight capacity would still qualify. The court chose the word appreciate 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. The Commonwealth need not prove both. Commonwealth v. Rezac, 494 Mass. 368, 371 (2024). The Supreme Judicial Court set out the model instruction in an appendix to Commonwealth v. Goudreau, 422 Mass. 731, 737 to 738 (1996). The Model Jury Instructions on Homicide (2018) repeat that instruction. Judges put the question to the jury in those terms.

The jury decides the defendant’s capacity as of the moment of the conduct. A defendant may have been ill for years before the offense and may be ill at trial. Neither fact establishes the defendant’s condition at the moment of the act. The question 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. Judges instruct juries accordingly. Commonwealth v. Loya, 484 Mass. 98 (2020).

The jury also answers the question 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. The jury 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 alone does not establish lack of criminal responsibility.

Some conditions are excluded. In McHoul, the Supreme Judicial Court adopted the Model Penal Code’s exclusion of an abnormality manifested only by repeated criminal or otherwise antisocial conduct. A history of offending is therefore not itself a mental disease. Drug addiction, standing alone, is not a mental disease or defect. Commonwealth v. Sheehan, 376 Mass. 765 (1978).

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. The jury analyzes a mental defect under the same McHoul standard. The parties usually dispute whether a personality disorder qualifies, 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 jury applies the McHoul standard to postpartum illness as to any other condition. The jury decides whether the condition was a mental disease and whether, at the time of the act, the condition deprived the defendant of substantial capacity. 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 associated with bipolar disorder and with a prior psychiatric history. A depression with psychotic features is more severe than postpartum depression and less severe than postpartum psychosis. Counsel ask the experts which condition the defendant had and how far the condition had progressed on the day in question.

The evidence in these cases is largely documentary. Both experts work from the 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.

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

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

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. The prosecutor points to ordinary functioning in the surrounding days, such as appointments kept, messages sent, and children cared for. The prosecutor asks whether any clinician documented psychosis before the offense rather than after the arrest. The prosecutor also looks for evidence of 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

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 judge may exclude the defense expert if the notice is late.

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. The judge may instead order the defendant hospitalized for observation for up to 20 days, a period the judge may extend 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. The court seals the examiner’s report until the defendant offers the expert evidence at trial. The judge may bar a defendant who refuses the examination from presenting expert testimony based on the defendant’s statements.

At trial, the judge submits the question 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. The defendant need not call an expert to raise the defense. Commonwealth v. Mattson, 377 Mass. 638, 644 (1979); Commonwealth v. Monico, 396 Mass. 793, 798 (1986).

In practice defense counsel presents the defense through a psychiatrist or psychologist who examined the defendant, reviewed the records, and can testify in the terms the McHoul standard requires. The Commonwealth’s burden on this issue arises only after the evidence has raised the defense. Defense counsel therefore ordinarily waits until the close of all the evidence to make a motion for a required finding of not guilty on the ground that the Commonwealth did not prove criminal responsibility. Commonwealth v. Lawson, 475 Mass. 806 (2016). The Commonwealth is entitled to rebut the defense evidence before the judge measures the sufficiency of the Commonwealth’s evidence.

The Commonwealth’s Burden

Once the defense is in the case, the Commonwealth must prove criminal responsibility beyond a reasonable doubt. The Commonwealth meets that burden by proving one of two things: that the defendant had no mental disease or defect, or that the disease or defect 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 same allocation of the burden applies to self-defense once a defendant raises that defense.

For many years judges told juries of a presumption of sanity. In Lawson, the Supreme Judicial Court ended that practice. The presumption is only an inference from the fact that most people are sane. The inference is not enough by itself to prove criminal responsibility. Judges may not instruct juries about the presumption. 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. The judge may not tell the jury to begin from that assumption.

The Commonwealth need not call an expert. The Commonwealth may prove criminal responsibility through the facts of the offense and the defendant’s conduct. 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). Juries therefore often decide these trials on the conduct evidence rather than on the diagnosis.

How Prosecutors Attack the Defense

In Lawson, the Supreme Judicial Court listed the kinds of evidence from which a jury may infer criminal responsibility. The list describes how prosecutors try these cases. The list 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).

The prosecutor develops each item 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 the offense. The Commonwealth argues that a person who did those things understood what they were doing and was able to choose.

The prosecutor cross-examines the defense expert on the foundation of the opinion. The prosecutor asks how much of the opinion 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 establishes that the defendant was well. Each question 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. The jury then decides the case largely on the conduct evidence.

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

Courts enforce limits on the prosecutor’s closing argument. 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

Neither voluntary intoxication nor addiction is a mental disease or defect. 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. In Commonwealth v. DiPadova, 460 Mass. 424 (2011), the Supreme Judicial Court stated the rules for those cases.

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 the substances would have that effect. 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 question is what this defendant knew about the effect of these substances on this illness, not what a reasonable person would have known.

Substance use is a frequent feature of these cases. The Commonwealth will argue that the substances, rather than the illness, caused the incapacity. The parties often contest the instruction the judge gives the jury on the point. Defense counsel who 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 the jury can consider. In a murder case, the jury may consider evidence of mental impairment on whether the defendant deliberately premeditated and on whether the defendant committed the killing 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. Defense counsel ordinarily presents the two arguments 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. The Supreme Judicial Court has reduced verdicts under that section because of evidence of serious mental illness, as in Colleran, where the court reduced a first-degree murder conviction to murder in the second degree for a mother with profound psychotic depression. The Supreme Judicial Court conducts that review only in first-degree murder cases. The possibility of that review is one reason defense counsel develops the illness evidence 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 the jury finds that the Commonwealth proved the elements, the same jury hears the psychiatric evidence and decides criminal responsibility. Massachusetts trials are ordinarily unitary, with both questions tried together. A defendant who wants a bifurcated trial must ask the judge for one.

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

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 the offense. The jury hears the crime scene evidence and the psychiatric evidence together. The emotional weight of the crime scene evidence can overwhelm the psychiatric evidence. 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.

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. The concession is binding. Defense counsel therefore chooses that course only where the acts cannot realistically be disputed. The defense in the Lindsay Clancy case asked for a two-part trial. The judge refused the request, and a single jury tried the case.

Trial Practicalities

A trial of this defense proceeds under the ordinary rules of Massachusetts criminal court practice, with several features of its own. The jury sees the defendant every day of the trial. The jury sees a person who is medicated, composed, and attentive. That appearance 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 judge instructs the jury about what happens after 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. Massachusetts has no verdict of guilty but not criminally responsible. A verdict slip that suggests such a verdict 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 from an ordinary trial, because the judge or counsel may question prospective jurors 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. The case ends in the criminal court. A civil commitment proceeding under G.L. c. 123, § 16 then begins. The district attorney remains a party to that proceeding.

Under § 16(a), the court may order the person hospitalized for observation for 40 days. The court may send a man who requires strict security to Bridgewater State Hospital. Otherwise, the court places the person in 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. During the observation period, the facility evaluates the person and decides whether to petition for commitment.

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 the person if the court 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), each further commitment lasts one year. The court may renew the commitment without limit while the person continues to meet the standard.

A committed person is a patient, not a prisoner, but the district attorney’s involvement continues. Under § 16(e), the facility may lift restrictions on the person’s movement within the facility grounds 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. Counsel therefore must advocate for release. A civil commitment can last longer than the sentence a judge could have imposed on a conviction for the offense.

Two consequences result from the commitment rather than from 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 a court grants relief 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 defense did not dispute the acts. 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 judge refused the defense request for a bifurcated trial. The jury reported that it could not agree, and the judge declared a mistrial.

Three pages on this site discuss 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 third, the mistrial page, states the rules that govern a mistrial after deadlock and the retrial that may follow.

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.