Lindsay Clancy’s defense implies she heard ‘command hallucinations.’ What are they?

A person can appear lucid and make plans despite hearing voices directing their behavior, experts say.

A woman left flowers at a makeshift shrine in front of the Clancy home last month.Matthew J. Lee/Globe Staff

Did Lindsay Clancy commit premeditated murder or was she commanded by voices in her head when she allegedly strangled her three children to death last month? That question will be at the crux of the legal proceedings against the Duxbury woman, as laid out in separate arguments by prosecutors and her defense team at Clancy’s arraignment on Tuesday.

But experts in psychosis say the two arguments aren’t mutually exclusive: People can appear lucid, premeditated in their behavior, and still be in the grip of powerful delusions.

At the arraignment in Plymouth District Court, prosecutors revealed that Clancy told her husband she heard a man’s voice in her head telling her to kill the children and then herself, because “it was her last chance,” Assistant District Attorney Jennifer L. Sprague said.

Known as command hallucinations, these voices are signs of psychosis, experts say. They are “telling you to do things, telling you things that are malevolent, and you believe those voices,” Paul Zeizel, the psychologist hired by the defense, told reporters Tuesday. People who hear such voices can feel compelled to obey them, he said. Zeizel added that he is still evaluating Clancy and has not reached a diagnosis.

But prosecutors are trying to undermine the defense’s claim Clancy was in the grip of psychosis. Quoting sources who described her as acting “normal” on the day of the killings, Sprague argued during the arraignment that Clancy demonstrated “deliberate premeditation and extreme atrocity and cruelty,” because she planned the attack.

To get more time alone with the children, Sprague said, Clancy sent her husband to pick up food at a restaurant that was farther away than the places where they usually went.

But Zeizel said that people with severe mental illness can still “present as being lucid and linear and clear thinking.”

And two forensic psychiatrists not involved with the case said in interviews that making plans does not exclude the possibility that a person is in thrall to psychotic delusions.

“The fact that you’re psychotic doesn’t mean you’re suddenly incapable of any rational thought altogether,” said Dr. Liza H. Gold, a Georgetown University clinical professor of psychiatry.

To send her husband out for food so he won’t stop her from doing something she feels compelled to do is very different than, say, buying a ticket to Canada where a boyfriend is waiting, said Gold, a former president of the American Academy of Psychiatry and the Law. Most mothers who kill their children are not seeking a better life; they intend to end their own, as well, Gold said.

Clancy had slit her wrists and throat before jumping out the window in an apparent suicide attempt. “When you see there is a murder-suicide going on, that’s usually profound psychosis, and it’s not unusual to find a command hallucination,” Gold said.

“Planning can happen along with delusions,” agreed Dr. Jeffrey S Janofsky, director of the Psychiatry and Law Program at Johns Hopkins Medicine. “The mere fact that they planned it does not exclude an insanity plea.”

Janofsky noted that command hallucinations are merely a symptom and not a defense on their own. “You have to figure out what the illness is.”

These types of hallucinations are usually a feature of psychosis, which can take many forms, Gold said. Sometimes it manifests as disorganized thoughts and vague hallucinations that change from one thing to another. Often people hear voices — sometimes strange voices, sometimes familiar ones. The voices offer comments and observations, often criticizing the person hearing them. Sometimes the voices give instructions.

“You hear a voice telling you to do something. It repeats over and over. ‘You’re a terrible mother. Your children are going to hell unless you kill them now,’” Gold said. A person might resist the commands for some time until they become overwhelming.

“If you’re acting at the behest of a command hallucination, how much agency do you really have?” she said.

Sprague, the prosecutor, also noted that Clancy asked whether she needed a lawyer on Jan. 27, the day her youngest child died, showing that she had “the clarity, focus, and mental acumen to focus on protecting her own rights and interests.”

That may be true, Gold said, but she could still be suffering from delusions at the same time.

A patient in such circumstances may be aware they did something wrong but felt they were choosing between two evils, Gold said. They may believe their children would have been damned to hell if they hadn’t killed them. Other times a woman might plan a suicide believing the world is better off without her but fears her children will be abused if she leaves them behind.

“It’s not usually, ‘I hate these children. I have to get rid of them.’ It’s usually out of a sense of duty, obligation, responsibility. They do understand that other people won’t understand it,” Gold said.

The defense has argued that overmedication led to the killings. Gold doesn’t think that’s likely, although she does not know all the details. “She could have been overmedicated, but that would not have caused command hallucinations,” she said. One of Clancy’s medications, Seroquel, is an antipsychotic, although in low doses it’s sometimes used to combat anxiety or aid sleep.

Clancy had also been taking benzodiazepines, which treat anxiety and insomnia. “It is possible that withdrawal from chronic benzodiazepine use could cause psychotic symptoms, including auditory hallucinations,” Janofsky said.

At Tuesday’s arraignment, Clancy’s defense lawyer, Kevin Reddington, repeatedly raised the issue of her mental status, but he did not explicitly say that he was planning to mount a defense of not guilty by reason of insanity.

Gold said that would be difficult, given that killing one’s children sparks deep outrage because it runs contrary to the expectations of mothers. “To plead not guilty by reason of insanity is a Hail Mary,” Gold said. “Those cases have a very limited success rate. . . . When it goes against the gender stereotypes it’s even more difficult.”

Laura Crimaldi and Travis Andersen of the Globe staff contributed to this report.