UnitedHealthcare CEO murder suspect Luigi Mangione’s "only viable chance" of success in his murder case is "some type of psychiatric defense," according to New York-based attorney Daniel Gotlin.

Gotlin, of Gotlin & Jaffe, successfully tried a mental health defense in 2014 while representing a man accused of fatally stabbing his mother.

"My guess is they should try some kind of psychiatric defense where it mitigates his intent to do this in the hopes that instead of getting convicted of murder, he gets convicted of manslaughter," he told Fox News Digital. "Even if he gets the maximum, which is eight to 24 years ... he could still get out. You know, you may spend 15, 16 to 18 years in, but at least one day you're going to get out."

Manhattan District Attorney Alvin Bragg on Tuesday announced that a grand jury indicted Mangione on one count of first-degree murder, in furtherance of terrorism; two counts of second-degree murder; two counts of second-degree criminal weapons possession; four counts of third-degree criminal weapons possession; one count of fourth-degree criminal weapons possession; and one count of second-degree criminal possession of a forged instrument.

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Bragg called Mangione's alleged actions "premeditated" and "targeted" in a Tuesday statement.

Mangione faces additional charges involving the alleged murder weapon and forged identification in Pennsylvania, where he was arrested.

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Under New York law, first-degree murder charges are reserved for specific circumstances, such as the murder of a police officer or if the crime involved torture. Second-degree murder is the charge for intentional murder and still carries a maximum penalty of life in prison.

"Anybody who thinks they're going to win the case based on facts [is] either incompetent or just completely out of their minds," Gotlin said. "There is no way that that could happen, not the way I see the evidence."

Evidence collected by authorities so far includes a manifesto that Altoona, Pennsylvania, police apparently found in Mangione’s backpack when they arrested him at a McDonald’s location on Dec. 9. Officials also allege a 3D-printed gun and suppressor found on Mangione during his arrest match a description of the weapon used in Thompson’s murder.

Additionally, NYPD Commissioner Jessica Tisch said on Dec. 11 that police matched the gun recovered from Mangione in Pennsylvania to shell casings found outside the Hilton where Thompson was gunned down from behind on the sidewalk. They also have his fingerprints on a snack bar wrapper and a water bottle, she said.

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Mangione's own lawyer, before she was retained, predicted an insanity defense in a CNN interview.

"It looks to me like there might be a not guilty by reason of insanity defense that they're going to be thinking about because the evidence is going to be so overwhelming that he did what he did," Karen Friedman Agnifilo told the outlet.

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Her office declined comment to Fox News Digital. Mangione's Pennsylvania attorney, Thomas Dickey, has not responded to multiple requests for comment from Fox News Digital.

Still, others have suggested that the level of planning that appears to have gone into the slaying could make an insanity defense difficult.

"For example of an extreme emotional distress defense, a guy walks up to somebody on the subway and stabs somebody, then he drops the knife and stands there, and he's got previous mental health issues. He's hearing voices," said Louis Gelormino, a New York City criminal defense attorney who previously represented a client who stabbed both of his parents and argued such a defense. "He's not planning a getaway, he doesn’t have false ID, he doesn’t have a silencer on his weapon. Those are the things that show, no matter what you do, you did know what you were doing."

Another mental health option, but not necessarily a defense, would involve arguing that Mangione is unfit to stand trial, Gelormino said. If his lawyers succeed there, he would potentially be hospitalized until he's fit enough to go before the court and then go to trial anyway.

A masked gunman ambushed Thompson, who lived in Minnesota, outside a Manhattan Hilton hotel about an hour and 45 minutes before he was supposed to take part in the company's annual shareholder conference, which had been publicly announced. 

The suspect, who police believe was Mangione, checked into a hostel on the Upper West Side with a fake ID, paid cash and is believed to have escaped the Big Apple within an hour of the slaying.

The 26-year-old suspect is originally from Maryland and has recently lived in California and Hawaii. Mangione graduated valedictorian from the Gilman School, a private, all-boys high school in Baltimore, in 2016. He went on to receive his bachelor's and master's degrees in computer science from the University of Pennsylvania in 2020.

"Now, it seems to me that, based on what I see in this kid, he clearly had some kind of break with reality," Gotlin said. "Based on what I see, he had everything going for him. And ... I'm not a psychiatrist. I've done other psychiatric cases. I mean, it's conceivable he's developed schizophrenia or some kind of psychiatric disorder over the last several years and is completely delusional."

According to the National Institute of Mental Health, most schizophrenia cases are diagnosed between the ages of 16 and 30, although males typically develop the condition at the earlier half of that range.

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Experts say it's too early to speculate about a potential defense or plea deal, or even a motive for that matter, despite an alleged manifesto in the suspect's handwriting.

"Right now is too early to make a decision on pleading him out because he may not have been of sound mind at the time of the shooting," said Lara Yeretsian, a Los Angeles-based criminal defense attorney who has represented high-profile defendants including Michael Jackson and Scott Peterson. "What untethered thinking could have caused Luigi Mangione to go after an insurance executive? There is nothing to indicate he was denied coverage, and we know he comes from an affluent background, so money was not an issue."

"Even though he had written a manifesto, the shooting may have been the product of a delusional and unsound mind, a defense his lawyers would have to consider before having him admit guilt," she added.