Lindsay Clancy’s case and the limits of the insanity defence: Why jurors can reach different conclusions

The murder case involving Lindsay Clancy has highlighted an especially challenging issue regarding the relationship between one’s mental well-being and their level of culpability in committing a crime – how to assess the degree of one’s guilt if the defence claims that a serious psychiatric disorder made them incapable of comprehending the nature of their actions and controlling themselves?

Former labour and delivery nurse Lindsay Clancy from Duxbury, Massachusetts, is charged with the murder of her three children, Cora, aged five years, Dawson, three years old, and Callan, only eight months old, committed in January 2023. She confessed to having killed her children, yet her defence claims that it was due to suffering from postpartum psychosis and a lack of control over herself.

However, prosecutors produced evidence showing that she was acting intentionally and comprehended the nature of her actions, Reuters and the Associated Press report.


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Her first trial ended in a mistrial on September 4, 2026, since the jurors could not reach a unanimous verdict.

Reports by the jurors revealed that 11 jurors favoured the decision to rule that Clancy was not criminally responsible as a result of mental disorder, while there was only one juror voting for conviction. This meant that there was no agreement in the courtroom, thus leaving the issue of weighing psychiatric evidence against evidence of planning and behaviour open.

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On November 2, when Clancy came to court, the legal wrangle continued.

In the case, her lawyers wanted the case dropped, citing issues of double jeopardy. The prosecutors, however, were against dropping the case. The hearing also raised the issue of a retrial despite prosecutors not having declared their intentions for this course of action.

Why an insanity defence is about legal responsibility, not simply a diagnosis

Not all cases where an individual is diagnosed with a psychiatric disorder mean that the individual is exempt from criminal responsibility. There has to be an inquiry into whether the condition fulfilled the requirement of being insane according to the legal standards during the commission of the crime.

In Massachusetts, the defence is referred to as “lack of criminal responsibility.”

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According to the legal criteria of the state, the prosecution needs to establish the guilt of the accused beyond a reasonable doubt by showing that the individual was criminally responsible. Being criminally responsible implies that the accused was capable of understanding the wrongfulness of their actions or could comply with the law.

In Clancy’s trial, experts in the defence claimed that Clancy had suffered from postpartum psychosis and that her mental condition had significantly impacted her capability to exercise self-control.

On the contrary, the prosecution’s experts disagreed with this assertion, claiming that Clancy acted out of premeditated plans and knew what she was doing was morally wrong. The two conflicting assertions gave the jury the duty of deciding not only whether Clancy had a mental disorder but its significance in terms of criminal responsibility.

The case also reveals the contrast between different jurisdictions within America.

In Massachusetts, it is the prosecutor’s obligation to show the responsibility of the criminal after the defendant has raised this matter, which is contrary to other jurisdictions, where the defendant has to prove his/her sanity. As noted in a report by WBUR, Massachusetts follows a unique legal system compared to others in the country.

Conflicting expert testimony helps explain why jurors may disagree

The assessment of psychiatric evidence is particularly challenging for the jury since one cannot resolve the issue regarding an individual's state of mind, intentions or the capacity to control one's actions simply by means of a diagnosis.

During the prosecution of Clancy's case, psychiatrists working for the defence described several symptoms characteristic of postpartum psychosis as well as claims that Clancy had experienced hallucinations with an instruction to commit the murders.

A forensic psychiatrist for the defence suggested that she could not control her behaviour owing to her mental disorder. The prosecution rejected the interpretation of the defence, arguing that there was evidence indicating Clancy had planned the murders and understood the nature of her actions.

The experts, therefore, were tackling similar but different issues: whether Clancy had a mental disorder, how that disorder impacted her functionality, and whether those impacts met the criteria for insanity as it pertains to a lack of criminal responsibility.

A juror could believe that an individual had a mental disorder but yet did not agree that the mental disorder made it impossible for the individual to understand the criminal nature of his or her conduct or to control their actions.

This may have been one reason why the jury was unable to come to a consensus.

Several jurors stated afterwards that they believed Clancy to be not criminally responsible, but the one juror who refused to agree believed that the evidence warranted the guilty verdict. Both statements illustrate the difference between the jurors, but neither proves that the way the evidence was interpreted by each side was legally valid.

The fact is that the jury could not reach a unanimous verdict.

What the mistrial means for Clancy and the next stage of the case

A mistrial is not equivalent to an acquittal; this signifies that the case was terminated without reaching a verdict, allowing the prosecution to choose whether they will retry the case depending on the court ruling and laws.

Clancy's lawyers claim that the judge should have conducted more investigations to determine the issues faced by the jury before declaring a mistrial.

This is because the ruling might make a second trial impossible due to the double jeopardy principle. The prosecutors assert that the judge followed the procedure by terminating the trial after being informed that the jury could not reach a verdict.

This issue is not only about reaching the correct verdict but the boundaries within which a judge can act when jurors do not reach an agreement. The question is whether it is possible and necessary to investigate the thoughts of the holdout juror.

In October, Judge William Sullivan turned down the request for an evidentiary hearing regarding the behaviour of the holdout juror.

During the 2nd hearing held on November 2, the defence restated its reasons for dismissal while the prosecution stood by its claim that a mistrial was rightly called. The ruling of the court on the motions will provide an answer on whether the case will proceed, and what options will be open for both parties.

According to Reuters, the prosecution did not make known whether they would pursue a new trial on charges of first-degree murder or file lesser charges.

The question that lingers in the Clancy case is whether her condition when she committed the murders made her not criminally responsible as per Massachusetts law. The calling of a mistrial shows just how complicated it is for jurors to come up with a decision based on psychiatric evidence.

A mistrial will neither answer the medical questions nor the results of future proceedings.