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COHASSET, Mass. – The Massachusetts art swindler accused of misleading authorities in their search for his long-missing wife was once called a "sociopath" by the beneficiary of his father’s will, raising some questions about his mental health. But how difficult would a mental health defense be to achieve?

Daniel Gotlin, a noted New York-based defense attorney, successfully tried a mental health defense in 2014. At the time, he was representing a man accused of fatally stabbing his mother after she began limiting his soda intake and cigarette smoking. 

"Most of our clients are sociopaths, that means you’re just putting your interest above society," Gotlin told Fox News Digital. "It doesn’t mean you’re insane when you a commit a crime."

TIMELINE OF ANA WALSHE'S DISAPPEARANCE AND BRIAN WALSHE'S ARREST

A man wearing a grey t-shirt is held by the arms by two police officers

Brian Walshe is led into Quincy District Court in Quincy, Massachusetts, Monday, Jan. 9, 2023.  (David McGlynn for Fox Digital)

Brian Walshe, 47, remains behind bars for allegedly misleading law enforcement investigating his wife’s Jan. 1 disappearance. The woman, 39-year-old Ana Walshe, has been missing for 12 days.

Brian Walshe was arrested on Jan. 8 and charged with misleading a police investigation into her disappearance. He was ordered held on $500,000 cash bail over $5 million surety bond. He has not been charged with anything related to his wife’s wellbeing. 

The previously convicted art swindler, who shares three young boys with his missing wife, was on house arrest at the time for selling fake Andy Warhol paintings.

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Walshe was further accused in 2018 of destroying his neurologist father’s will in 2018, after he was cut out of the man’s estate.

Ana Walshe's pool being drained

Individuals could be seen draining the pool at Ana Walshe's Cohasset home; Walshe has been missing since New Year's Day.  (David McGlynn for Fox News Digital)

When Dr. Thomas Morecroft Walshe died unexpectedly, he left his son "my best wishes but nothing else" and an ensuing court battle over his will. Thomas’ longtime friend, who was the beneficiary of the will, later described in court how he had "witnessed firsthand what Brian was capable of."

"I saw Brian attempt to smuggle out antiquities from China," the man wrote. "When Brian was confronted, he picked up a stanchion and literally attempted to kill four or five guards that had come to talk to him about his crime." 

Ana and Brian hold their children and blow out birthday candles

Ana and Brian Walshe blow out candles on a birthday cake with their children in an April 2020 Instagram post.  (Ana Walshe/Instagram)

He added: "Brian is not only a sociopath, but also a very angry and physically violent person," court papers state. 

But despite the accusations regarding his mental health, Gotlin said Walshe "has no insanity defense."

ANA WALSHE SAID HUSBAND WAS 'TAUGHT TO LIE' AND 'TOLD HE WAS A LOSER' AS A CHILD: COURT DOCS

Man who appears to be Brian Walshe drives in red car

A man who appears to be Brian Walshe drives away from the Walshe home at 516 Chief Justice Cushing Highway, Cohasset, MA. He is in a friend or relative's car. Law enforcement appeared to have moved family out of the house to investigate its contents. (David McGlynn for Fox News Digital)

"There’s too much planning in it," he said. "Insanity happens on the spur of the moment."

Gotlin referenced a recent CNN report that described how Walshe had conducted internet searches for "how to dispose of a 115-pound woman's body" and how to dismember a body. Gotlin also noted that investigators do not need a body to provide their case if they have strong circumstantial evidence. 

"He may just be a sick sociopath that really has no defense, and the only defense is to work out the best disposition," Gotlin went on.

Duncan Levin, also a New York-based criminal defense attorney, stressed that the case was still in "such early stages" to the point where Ana Walshe or her remains have not yet been located. 

Ana and Brian Walshe take a selfie with friend in a restaurant

Ana and Brian Walshe pictured in a 2015 Facebook post.  (Ana Walshe/Facebook)

"It’s hard to predict exactly what the defense is going to be," he said. "But clearly, whether it’s a defense to the charge or something to try to mitigate whatever punishment there could be down the line, his history of mental issues will all come to play." 

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Levin, who has represented high-profile names including disgraced producer Harvey Weinstein, added that a mental health defense "is very difficult to show." 

"Already, what we know is that this is somebody who has shown, according to the evidence that's already been brought forth, this is somebody who has Googled how to dismember a body and bought cleaning supplies to try to cover up the crime," he said. "It’s not something that a mentally ill person would do."

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He added: "Given the evidence we know, a mental health defense is going to be exceedingly difficult, if not impossible."