NEW YORK — Luigi Mangione pleaded not guilty Friday to the murder of UnitedHealthcare CEO Brian Thompson in his federal death penalty case — as a judge warned government prosecutors to tell their bosses to heed the high-profile defendant’s right to a fair trial.

Before a packed courtroom in Manhattan federal court, the 26-year-old, wearing beige prison garb with a white long-sleeved shirt underneath, stood and proclaimed he was not guilty of murder through the use of a firearm — which is death penalty eligible — stalking and related offenses.

“Not guilty,” Mangione said after telling Manhattan Federal Judge Margaret Garnett he understood his rights.

In an April 1 press release — weeks before Mangione had been indicted — Attorney General Pam Bondi said the Justice Department would seek the death penalty against him, the first sought since President Donald Trump’s return to power, which Mangione’s attorneys have argued was premature and prejudiced his right to find an impartial jury.

The prosecution didn’t formally file their intent to seek capital punishment with the court until Thursday.

Garnett warned both sides about public commentary that could impede Mangione’s right to a fair trial, specifically telling Assistant U.S. Attorney Dominic Gentile to convey her directive to the new Trump-appointed head of the Southern District of New York prosecutor’s office, interim Manhattan U.S. Attorney Jay Clayton, and the AG herself.

“I’m specifically directing the government convey my directive to Mr. Clayton and request that he convey the same to Attorney General Bondi,” Garnett said.

The Maryland man has also been charged on the state level in an indictment filed by Manhattan District Attorney Alvin Bragg with murder and terror offenses, carrying the possibility of life without parole if he is convicted. He’s pleaded not guilty and is expected to go on trial first in that case, the feds said Friday. He also faces lower-level charges in Pennsylvania related to items he was allegedly in possession of upon his arrest.

Thompson was shot dead on Dec. 4 outside the Hilton hotel in Midtown, where the 50-year-old father of two was arriving for an annual investor conference, with the gunman fleeing the scene. Shell casings at the Midtown scene bore the words “deny,” “defend,” and “depose,” authorities say, in reference to the healthcare industry routinely denying claims to maximize profits.

Mangione, an Ivy League computer science graduate, was arrested five days later at a McDonald’s in Altoona, Pennsylvania, following a nationwide manhunt. State and federal authorities in New York and Pennsylvania allege he was in possession of a 3D-printed ghost gun, a silencer and ammunition matching that recovered at the scene, as well as a manifesto with writings critical of the health insurance industry.

Mangione has reached icon status among some Americans frustrated with the U.S.’s expensive health care system, raising nearly $1 million toward his legal defense.

Dozens of supporters turned up for Friday’s hearing, bearing placards outside the lower Manhattan courthouse with messages like “presumed innocent,” and the definition of jury nullification, which is when a jury votes not guilty even if they believe the defendant broke the law.

On Friday, Mangione’s lead attorney, Karen Friedman Agnifilo, said the defense wanted the federal case to go to trial first. She has heavily criticized the dueling prosecutions and the prospect of double jeopardy, arguing that she has to present arguments for charges of a different nature that could harm Mangione’s respective defense strategies.

Agnifilo, who declined to comment after the hearing, also told Garnett that she had recently learned that a fed had inadvertently listened in on an attorney-client privileged call she had with Mangione from the Metropolitan Detention Center in Brooklyn.

“We were just informed by state court prosecutors that they were eavesdropping on all of Mr. Mangione’s calls,” the lawyer said.

The judge gave prosecutors seven days to file a letter with the court explaining what happened and 30 days to hand over discovery, setting other deadlines in September. She scheduled Mangione’s next federal court hearing for Dec. 5, when she said she would set a trial date for sometime in 2026.

If Mangione is convicted at his federal trial, it will be a jury, not prosecutors, who will decide at a second trial, known as the death penalty phase, whether the state should execute him.

The last death penalty case tried by the Manhattan U.S. attorney’s office was in 2023 against Sayfullo Saipov for killing eight people on a West Side bike path. It took months for the parties to find New Yorkers who weren’t opposed to capital punishment, and the chosen panel ultimately couldn’t reach a unanimous decision. Saipov got a life sentence.

_____

©2025 New York Daily News. Visit at nydailynews.com. Distributed by Tribune Content Agency, LLC.