Shackled Luigi Mangione in packed court over healthcare CEO Brian Thompson's killing

A lawyer for Luigi Mangione, accused of killing UnitedHealthcare CEO Brian Thompson, has argued that the 26-year-old is not being granted the right to a fair trial.

The comments came during a brief procedural hearing on Friday, which drew hundreds of supporters - some from as far as Kansas - chanting the defendant's name and wearing shirts adorned with his face.

Mr Mangione arrived in court with his hands and legs shackled, wearing a green sweater and a bulletproof vest. He has pleaded not guilty to the New York charges.

The killing of Mr Thompson, 50, a husband and father of two, sparked a nationwide conversation about the US healthcare system, unleashing pent-up anger at the industry and some ugly reaction.

Chants from Mr Mangione’s supporters could be heard from the court’s 15th floor on Friday.

His brief appearance drew more people than the number that attended the public gallery in the same courtroom last year for President Donald Trump’s hush money trial.

Some of Mangione's supporters wore face masks and green Luigi hats, from the Super Mario video game franchise.

A court officer watching the spectacle muttered: "What a joke."

Among members of the public in court was Chelsea Manning, who was convicted more than a decade ago of espionage for leaking secret military files to Wikileaks.

Investigators say Mr Mangione was motivated to kill Mr Thompson because of anger with US healthcare insurance companies.

In addition to the New York state-level charges, Mr Mangione is accused of federal stalking and murder offences that could carry a death penalty.

The three separate cases were a source of frustration for Mr Mangione's lawyer, Karen Friedman Agnifilo, who argued before the packed court on Friday that her client was being treated differently than other defendants.

"His right to a fair trial is continuing to be impacted," she said at the hearing, which lasted less than 30 minutes.

She cited her client's detainment in federal custody and remarks made by city officials about the case as factors that could influence the proceedings.

At the beginning of the hearing to discuss a pre-trial schedule, Ms Agnifilo said her client should not have to be shackled while in court, arguing it denies him the presumption of innocence guaranteed to all defendants.

"He is a model prisoner" in federal custody, Ms Agnifilo said.

But Judge Gregory Carro said court security preferred for Mr Mangione to remain shackled.

Ms Agnifilo also took issue with Mr Mangione remaining in federal custody.

She said the federal jail made it harder for him to meet lawyers to prepare for his court appearances.

Prosecutors told Judge Carro that Mr Mangione was being held in federal custody in "consent" with the defence team.

"When they're hanging the death penalty over your head, you have no choice but to consent," Ms Agnifilo replied.

She told the court that prosecutors were still deciding whether her client should face such a punishment.

Mr Mangione's lawyer also complained that the chief New York City detective on the case and Mayor Eric Adams had spoken to HBO, the US TV network, about evidence that the defendant's legal team had not even seen yet.

During the proceedings, prosecutors went over the mountain of evidence they plan to present at trial, including DNA, police reports and photographs from the scenes of the crime, body camera footage, phone records and other materials.

The judge set a deadline of 9 April to submit pre-trial motions.

In addition to the New York cases, Mr Mangione also faces charges of forgery, carrying firearms without a licence, and other counts in Pennsylvania, where authorities arrested him at a McDonald's.

Police say he was in possession of a gun, bullets, multiple fake IDs and a handwritten document that expressed "ill will" towards corporate America.

Investigators say the words "deny", "defend" and "depose" were written on shell casings found at the scene of Thompson's murder.

Law enforcement sources said this could have been a reference to the "three Ds of insurance" - tactics used by companies to reject payment claims by patients.

A fundraiser for legal expenses for Mr Mangione - an Ivy League-educated member of a prominent Baltimore family - has raised over $500,000 (£395,000) since his arrest.

He is being held at the Metropolitan Detention Center Brooklyn, the same facility where Sean 'Diddy' Combs is awaiting trial on sex-trafficking charges.