How the insanity defense works in Lindsay Clancy's trial

As last verified on Aug. 26, 2026, Commonwealth v. Clancy was being tried in Plymouth Superior Court before Judge William F. Sullivan, with the public question usually phrased as whether Lindsay Clancy is using an “insanity defense.” That shorthand is doing too much work. This article is an explanation of Massachusetts criminal-responsibility doctrine as it applies to the trial record, not legal advice and not a verdict prediction. For the running procedural snapshot—charges, dates, judge, and trial posture—see the verified Clancy trial record.

The phrase “insanity defense” suggests a defense that, if accepted, simply excuses a defendant from punishment. Massachusetts law uses a different term and a more specific mechanism: “lack of criminal responsibility.” Judge Sullivan described the jury’s possible outcomes as guilty, not guilty, or not guilty by reason of lack of criminal responsibility, and he instructed jurors on the standard they must apply rather than asking them to make a general judgment about mental illness or sympathy.[1]

The doctrine is McHoul, not the television version of insanity

Massachusetts follows the rule from Commonwealth v. McHoul, reflected in the state’s model jury instruction on lack of criminal responsibility. The instruction asks whether, because of a mental disease or defect, the defendant lacked substantial capacity either to appreciate the criminality or wrongfulness of the conduct, or to conform the conduct to the requirements of law at the time of the offense.[2]

Those words matter. The jury is not asked whether Clancy had a diagnosis, whether postpartum psychosis is real, or whether psychiatric testimony sounds more compassionate than the prosecution’s theory. The McHoul inquiry is narrower: at the time of the alleged killings, did a mental disease or defect deprive her of substantial capacity in one of two legally recognized ways?

Postpartum psychosis is the live evidentiary setting in the Clancy trial, but it is not itself the legal test. A clinical label may help a lawyer or expert explain why one McHoul prong is satisfied. It does not replace the prong. For the separate clinical-legal mismatch—especially the dispute over sudden onset—see Does sudden onset postpartum psychosis break the insanity defense?.

Once the defense is raised, the Commonwealth carries the burden

This is the point most likely to be missed in a quick “insanity defense” explainer. In Massachusetts, once lack of criminal responsibility is properly raised, the Commonwealth must prove criminal responsibility beyond a reasonable doubt. Northeastern law professor Daniel Medwed has described that allocation as the reverse of the majority approach in other states, where the defendant generally bears the burden of proving insanity or its equivalent.[3]

That does not mean the defense has nothing to do. The defense has to put criminal responsibility in issue with evidence sufficient to require the instruction. Once it is in the case, however, the legal question changes. The prosecution is not merely proving that the charged acts occurred, or that the killings satisfy murder elements. It must also prove that Clancy was criminally responsible under McHoul.

The model instruction uses the familiar criminal-law burden: beyond a reasonable doubt.[2] Some commentary and older legal phrasing may describe the burden in terms of “moral certainty,” but the practical instruction to jurors is not that the defendant must prove illness. It is that the Commonwealth must prove responsibility once the issue is properly before them.

That allocation explains why the trial has placed so much weight on expert testimony, rebuttal experts, and the final phrasing of the jury charge. The prosecution can accept, for purposes of argument, that Clancy was profoundly unwell and still argue that McHoul is not met. The defense can concede devastating conduct and still argue that the Commonwealth has not proved criminal responsibility. For more on how that burden shapes the trial tactics, see How Lindsay Clancy’s defense attorney is shifting the burden and Kevin Reddington’s concession strategy in the Clancy trial.

The jury is not choosing between prison and freedom

The cleanest way to understand the verdict form is to remove the misleading binary. Jurors are not being asked to choose between “punishment” and “walking free.” In broad terms, the paths are these:

The guilty path still requires the usual degree analysis for murder. Massachusetts first-degree murder carries a mandatory sentence of life imprisonment without parole under M.G.L. c. 265, § 2.[4] In a case involving multiple children, the moral gravity is obvious, but the legal work remains particular: the jury must determine whether the Commonwealth proved the charged offenses and the necessary mental state, and whether it also proved criminal responsibility.

The ordinary not-guilty path is different from NGRLCR. A simple acquittal means the government failed to prove the charged crime. A lack-of-criminal-responsibility acquittal means something more specific: the government failed on the criminal-responsibility issue after that issue was properly raised. The distinction matters because the legal consequences are not the same.

What “not guilty by reason of lack of criminal responsibility” would trigger

A verdict of not guilty by reason of lack of criminal responsibility is an acquittal of criminal punishment, but it is not an ordinary release order. Massachusetts law provides for court-ordered psychiatric examination and hospitalization procedures under M.G.L. c. 123, including § 15, which governs examinations and reports in criminal proceedings.[5]

In practical terms, an NGRLCR verdict would send the case from the criminal-liability question into a state-supervised mental-health custody question. The court does not simply thank the jury and open the courthouse door. The next issue becomes whether the person requires hospitalization because of mental illness and dangerousness, subject to statutory procedure and later review.

That distinction is not cosmetic. USA TODAY quoted Boston defense attorney Mark Galperin explaining that if Clancy were found not guilty by reason of insanity, she would go to Bridgewater State Hospital for evaluation and could then be committed to a Department of Mental Health facility, with confinement potentially lasting for life depending on later findings.[1] The Atlantic made the same larger point through the Andrea Yates example: Yates was acquitted by reason of insanity in her 2006 retrial and remained in state psychiatric custody years later.[6]

The Yates reference is useful only for that limited proposition. It does not tell a Massachusetts jury what to do in Clancy’s case, and it does not make postpartum psychosis legally identical across jurisdictions. It does show why the casual phrase “she’ll walk” is wrong as a description of what an insanity acquittal can mean.

Where the live Clancy record fits into the doctrine

The trial posture matters because doctrine does not apply itself. Jury selection began July 20, 2026; the defense rested Aug. 21 after presenting its lack-of-criminal-responsibility case; and the case moved through rebuttal and late-trial motions during the week of Aug. 24.[7][8] Those dates explain why the legal standard has moved from a pretrial talking point to the central instruction the jury must use.

The prosecution’s rebuttal phase included expert testimony from Dr. Avram Mack and Dr. Kirk Heilbrun, reported during Aug. 21–25, 2026.[9] The defense also sought a mistrial, which Judge Sullivan denied on Aug. 24.[8] Those developments are trial mechanics, not changes in the governing standard. They matter because they frame the evidentiary contest over McHoul: what did Clancy appreciate, what could she conform, and what did mental disease or defect do at the relevant time?

The disputed closing question is therefore not whether the killings were tragic, whether the children deserve to be centered, or whether psychiatric testimony is emotionally difficult. Those things can all be true without answering the legal question. The closing-arguments issue is whether the Commonwealth proved criminal responsibility beyond a reasonable doubt under the Massachusetts standard. For the narrower verdict-stage dispute, see What the Lindsay Clancy closing arguments come down to.

The real stakes of the “insanity defense” label

The public shorthand is understandable. “Lack of criminal responsibility” is not a phrase built for headlines, and no one outside criminal practice talks that way. But the label can distort the stakes in both directions. It can make a psychiatric acquittal sound like mercy without control, and it can make a criminal conviction sound like the only institutional response available.

Massachusetts law is more exacting than that. If the jury convicts, the case remains in the punishment system. If the jury returns an ordinary not guilty verdict, the prosecution has failed to prove the charged crime. If the jury returns not guilty by reason of lack of criminal responsibility, the criminal punishment question gives way to court-supervised psychiatric custody and review.

So the Clancy trial is not testing whether mental illness is sympathetic, and it is not testing whether acquittal means freedom. It is testing whether the Commonwealth can prove criminal responsibility under McHoul. Every legally significant path leaves a state institution—the prison system, the court, or the mental-health commitment system—with power over what happens next.

References

1. Lindsay Clancy verdict: What happens next — USA TODAY, Aug. 24, 2026
2. 9.200 Lack of Criminal Responsibility — Mass.gov
3. Daniel Medwed on the Lindsay Clancy trial — Northeastern Global News, July 31, 2026
4. General Laws Part IV, Title I, Chapter 265, Section 2 — Massachusetts Legislature
5. General Laws Part I, Title XVII, Chapter 123, Section 15 — Massachusetts Legislature
6. Lindsay Clancy and the insanity defense — The Atlantic, August 2026
7. Lindsay Clancy’s defense rests at trial over whether postpartum psychosis drove her to killings — PBS NewsHour / Associated Press
8. Lindsay Clancy trial: Judge denies defense request for mistrial over intentional misconduct claim — 6abc / Associated Press
9. Lindsay Clancy trial: Rebuttal witnesses — NewsNation