Law and Severe Mental Illness: The Lindsay Clancy Trial

As a forensic psychologist, I have conducted hundreds of forensic evaluations, including in cases where a defendant has raised lack of criminal responsibility — or colloquially, the “insanity defense.” These cases are complex because having a mental illness by itself, even a severe mental illness, does not necessarily mean the person is not criminally responsible. 

On Jan. 24, 2023, a Massachusetts mother and labor and delivery nurse, Lindsay Clancy, fatally attacked her three children, Cora (age 5), Dawson (age 3), and Callan (age eight months). After using a knife to cut her wrists and neck, Clancy jumped from the second-story of her home, ultimately leaving her paralyzed and in a wheelchair. More than three years later, after weeks of testimony and seven days of jury deliberations, on Sept. 4, 2026, the trial ended in a mistrial. Eleven jurors voted to find Clancy not criminally responsible while one juror voted to convict under first-degree murder.

The Clancy case sparked significant public attention. On what felt like every social media and news platform, people weighed in on whether Clancy should be treated as a criminal, a mental health patient, or even as an innocent person. Conspiracy theories abounded. The case also raised broader questions about the state of mental healthcare and the treatment of mothers with postpartum mental illness.

While it would be inappropriate for me to offer an opinion on whether or not Clancy met the legal standard for lack of criminal responsibility, the case can inform how we talk about and think through cases involving severe mental illness. Often missing from the discourse and fervor around Clancy were the legal standards around criminal responsibility, burdens of proof, the rules of evidence, and even the legal question the jury was asked to consider. Much of the public debate focused on the emotional aspects of the case but most of these questions were legally distinct from the issues the jury ultimately needed to decide. See Commonwealth v. Odgren, 483 Mass. 41, 51-52 (2019).

The specific legal test for insanity defenses varies by jurisdiction. However, the legal threshold is generally high. Some states focus primarily on whether the defendant could appreciate right from wrong, while others also consider whether mental illness interfered with the defendant’s ability to control their conduct. The latter component is referred to as “the volitional prong.” 

In Massachusetts, where Clancy’s trial was held, once criminal responsibility is raised the prosecution must prove beyond a reasonable doubt that the defendant was criminally responsible at the time of the crime. See e.g., Commonwealth v. Berry, 457 Mass. 602, 612 (2010); See Commonwealth v. Odgren, 483 Mass. 41, 52 (2019).

A crime requires both misconduct (the “actus reus”) and a criminal mindset (the “mens rea). It is rare for a defendant to argue lack of criminal responsible, occurring in approximately 1 percent of cases involving felonies. This is because the defense requires that the defendant concede the alleged criminal misconduct, the bar for being legally “insane” is very high, and juries are often very skeptical of the defense

The term “criminal responsibility” is a legal term of art. To be adjudicated “not criminally responsible,” the defendant must have had a mental disease or defect, and due to that mental disease or defect, lacked the substantial capacity either to appreciate the wrongfulness or legal significance of their conduct. Or, alternatively, due to the mental disease or defect lacked the ability to conform their conduct to the requirements of the law. See Commonwealth v. McHoul, 352 Mass. 544. 

It is important to remember that “mental disease or defect” is legal terminology and not a clinical term or a psychiatric diagnosis. A person may experience auditory and visual hallucinations, for example, and still be criminally responsible. 

In my own forensic work, I have had clients with mental illness whose criminal responsibility defenses failed because their behavior prior to the crime, during the crime, or after the crime suggested that they understood that what they were doing was illegal and reflected hallmarks of rational decision making. For example, I’ve seen clients hide murder weapons to avoid detection, which suggested that they appreciated the illegality of their crime.  

However, under Massachusetts law, there is a distinction between knowing that the conduct was wrong and appreciating the criminality or wrongfulness of the conduct. An intellectual awareness that the conduct is illegal or morally wrong is insufficient to prove criminal responsibility. Instead, the Commonwealth must prove, beyond a reasonable doubt, that the defendant meaningfully recognized that the conduct was illegal or wrong. 

Massachusetts law also recognizes a separate volitional prong. Even if a defendant understood that their conduct was wrong, they may still lack criminal responsibility if, because of a mental disease or defect, they lacked the substantial capacity to conform their conduct to obey the law. 

This complex distinction was central to the Clancy trial. The defense argued that Clancy experienced postpartum psychosis, and that due to that condition, she was not criminally responsible when she killed her three children. The Commonwealth acknowledged that Clancy suffered from mental illness but disputed that Clancy’s mental illness resulted in a lack of criminal responsibility at the time of the killings. 

During the trial, forensic mental health experts came to different conclusions on this issue. Although there was a general consensus that Clancy suffered from a form of mental illness, the disagreement lay in whether that mental illness impacted Clancy’s ability to appreciate that her conduct was legally or morally wrong or whether she was able at the time of the offense to conform her behavior to the requirements of the law. 

The experts were able to testify and offer opinions on diagnosis, treatment, standards of care, and the relationship between mental health disorders and behavior. However, the question of whether Clancy was criminally responsible was a legal question, and was for the jury rather than the experts to decide.

Factors such as the severity of the mental illness before or after the offense, whether the case involved extreme or horrific violence, whether the victim(s) were particularly vulnerable, whether or not the defendant shows remorse, and whether we feel sympathy for the defendant may shape how we personally respond to a crime. However, these factors are not dispositive in the determination of criminal responsibility. Criminal responsibility is a much narrower question: whether because of a mental disease or defect the defendant lacked the mental capacities required under the law.