How Luigi Mangione's legal defence could take shape

Forensic and ballistic evidence that police say ties the accused murderer of healthcare insurance CEO Brian Thompson to the crime scene will make it difficult for his lawyers to mount a defence, former prosecutors and other legal experts say.

Luigi Mangione, 26, was arrested in Pennsylvania on Monday after a days-long, multi-state manhunt ended at a McDonalds in the town of Altoona.

New York authorities say fingerprints and shell casings link him to the crime scene.

His lawyer, Thomas Dickey, earlier told local media he had not "seen any evidence yet" implicating his client.

He said Mr Mangione would plead not guilty to the charges he faces in Pennsylvania, including firearms charges.

In New York, he has been charged with second-degree murder over Mr Thompson's killing and it is not clear how he would plead. He is currently being held in a state prison in Pennsylvania where he is fighting extradition to face that murder charge. The legal battle over his extradition could potentially take more than a month to resolve, officials said.

But legal experts told the BBC that his efforts to contest his extradition to New York are unlikely to be successful. They could, however, provide his defence with a glimpse into the state's evidence against him.

"I don't even know if this is him," his lawyer, Mr Dickey, said in a recent interview with US media outlet NewsNation, referring to images of Mr Thompson's killer.

"We're going to test those waters and give the government a chance to bring some evidence forward," he said.

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• Who was UnitedHealthcare CEO Brian Thompson?

If he is extradited to New York to face the murder charge, Mitchell Epner, a New York-based lawyer and former prosecutor, told the BBC that there are, broadly, two approaches that Mr Mangione could take if he pleads not guilty.

"Defence number one is 'it wasn't me' and defence number two is 'it was me, but I shouldn't be punished' because of X," he said.

According to New York police, Mr Mangione was found with a gun similar to the murder weapon, a silencer and a fake ID, as well as three handwritten pages which they believe suggest a potential motive.

Mr Epner said that the publicly known evidence so far means denying responsibility is "out the window".

Another New York-based lawyer, criminal defence attorney and Professor Dmitriy Shakhnevich, said Mr Mangione's attorney could also, in theory, argue that an impaired "mental status" makes him unfit to stand trial.

"If a judge makes a determination that he's misunderstanding, or not understanding, what's happening in court, then essentially the case won't go forward," he said.

"He'll be institutionalised for a period of time until he's deemed to be fit, which may be never."

That defence, Mr Shakhnevich added, is different to a plea of insanity, in which his lawyers could argue that "he's not responsible for his actions because of some mental defect".

"That could also deem him not guilty, because you won't satisfy the elements of the offence," he said. "But then again, he doesn't go free. He would be institutionalised for a period, assuming that defence is successful."

The start of Mr Mangione's legal battles has prompted anonymous donors to chip in thousands of dollars towards his defence through online fundraisers.

It comes as some online have shared support for the suspect and anger at the health insurance industry. The New York City Police Department has also warned some healthcare executives are potentially in danger because of a "hit list" posted online after Mr Thompson's murder.

In a bulletin, the NYPD said several viral posts included the names and salaries of other insurance executives. Mocked-up wanted signs featuring some executives have also been posted in Manhattan.

Mr Mangione allegedly had grievances with the wider industry.

Timothy Gallagher, a former FBI agent and the managing director of Nardello and Co, a global investigations firm, said the current climate means the "threat of a copycat is real".

"There are people out there who have grievances and are observing the amount of press and attention that is being given to the accused," he said.

Mr Gallagher said that there has been an "outpouring of support from dark corners of the internet" for anti-corporate causes.

"I'm afraid that may fuel follow-on attacks," he said.