Luigi Mangione has pleaded not guilty to murdering a US healthcare chief executive - as prosecutors formally confirmed they plan to seek the death penalty for him.
The 26-year-old defendant appeared in a Manhattan federal court for an arraignment over the killing of Brian Thompson in New York last year.
Mangione has previously pleaded not guilty to a separate New York state indictment he faces over the murder of Mr Thompson, the boss of UnitedHealth's insurance division.
While public officials condemned the killing, some Americans - and people elsewhere across the world - have lauded Mangione, saying he drew attention to steep US healthcare costs and the power of health insurers to refuse payment for some treatments.
In justifying their decision to seek the death penalty, prosecutors wrote in their filing that Mangione "presents a future danger because he expressed an intent to target an entire industry, and rally political and social opposition to that industry, by engaging in an act of lethal violence".
US attorney general Pam Bondi earlier this month announced that the Justice Department would seek the death penalty for Mangione.
Mangione's lawyers did not immediately respond to a request for comment on Thursday.
They have said Ms Bondi's announcement on 1 April was "unapologetically political" and breached government protocols for death penalty decisions.
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If Mangione is convicted in the federal case, the jury would determine in a separate phase of the trial whether to recommend the death penalty.
Any such recommendation must be unanimous, and the judge would be required to impose it.
Mr Thompson was shot dead on 4 December outside a hotel in Midtown Manhattan, where an investor conference for the company was planned.
The killing sparked a five-day manhunt that captivated Americans.
Police officers in Altoona, Pennsylvania, found Mangione with a 9mm pistol and silencer, clothing that matched the apparel worn by Thompson's gunman in surveillance footage, and a notebook describing an intent to "wack" an insurance company CEO, according to a court filing.
(c) Sky News 2025: Luigi Mangione pleads not guilty to murder of healthcare boss - as death penalty bid confirmed
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