What the Lindsay Clancy Trial Is Testing About Insanity Defense Law in Massachusetts
The murder trial of Lindsay Clancy turns on a difficult legal question: whether a severe mental disorder left her unable to understand the wrongfulness of her conduct or control her actions when her three children died in January 2023.
Clancy, a former labor and delivery nurse from Duxbury, Massachusetts, faces three murder charges. The prosecution alleges that she killed her children at the family home and then attempted to end her own life. The defense has not centered its case on mistaken identity or an accidental death. Instead, attorney Kevin Reddington argues that Clancy was suffering from bipolar disorder and postpartum psychosis and should not be held criminally responsible.
The prosecution completed its case before the defense began calling witnesses in August 2026. According to the Associated Press, defense testimony has focused on Clancy’s deteriorating mental health, her treatment, and concerns raised by relatives and others before the killings. Prosecutors have presented a competing account, arguing that her conduct showed planning and awareness rather than a loss of legal responsibility. The evidence remains for the jury to weigh, and testimony reported during trial is not a finding of fact.
Massachusetts uses a demanding but unusual legal test
Massachusetts does not require a defendant to prove insanity by a separate “preponderance of the evidence” standard. Under the state’s model jury instructions, once evidence raises a genuine question about criminal responsibility, the Commonwealth must prove beyond a reasonable doubt that the defendant was legally responsible at the time of the offense.
The test comes from the Massachusetts Supreme Judicial Court’s decision in Commonwealth v. McHoul. Jurors must consider whether a mental disease or defect substantially impaired either of two abilities:
- the ability to appreciate the criminality or wrongfulness of the conduct; or
- the ability to conform conduct to the requirements of the law.
A medical diagnosis alone does not decide the issue. The jury may consider psychiatric testimony, medical records, witness observations, communications, and the defendant’s actions before and after the alleged crime. The central question is the defendant’s mental state at the specific time of the killings—not simply whether she had a history of depression, anxiety, medication changes, or other symptoms.
Why postpartum psychosis matters to the case
Postpartum psychosis is a rare psychiatric emergency that can involve delusions, hallucinations, severe confusion, and rapidly changing behavior after childbirth. The Massachusetts Department of Public Health says the condition requires evaluation by a health professional and does not have a validated screening tool specific to postpartum psychosis.
That medical uncertainty creates a courtroom challenge. Experts may disagree about whether symptoms reflected psychosis, another disorder, medication effects, or a combination of factors. Jurors must then decide not only what condition existed, but whether it removed the legal capacities required for criminal responsibility.
If the jury finds Clancy guilty, the case proceeds as a murder conviction. If it finds her not guilty by reason of a lack of criminal responsibility, that does not necessarily mean she would immediately leave custody. Massachusetts law provides for court-supervised commitment and treatment procedures for people found not criminally responsible. The verdict will therefore address both the deaths and the legal boundary between mental illness and criminal accountability.
Sources
- Lindsay Clancy was 'begging for help' before killing her children, former mother-in-law testifies
- Model Jury Instructions on Homicide: Criminal Responsibility
- Instruction 9.200: Lack of Criminal Responsibility
- Duxbury Woman Indicted on Charges That She Murdered Her Three Children
- Perinatal Mood and Anxiety Disorder Initiative