Luigi Mangione back in court as key questions remain over case ahead of murder trial

Luigi Mangione, the man accused of gunning down UnitedHealthcare chief executive Brian Thompson, is back in court in New York ahead of his murder trial, which begins next month.

A judge on Tuesday could hash out more ground rules for the trial and other aspects of the case, which has attracted national attention.

It has also created an online frenzy, with both his backers - many of whom see Mangione as a symbol of the backlash against US healthcare costs - and his critics analysing everything from his intentions to his appearance.

The case is likely to become an even bigger spectacle when jury selection for the trial begins on 8 September.

Mangione, if found guilty, could face decades behind bars. He has pleaded not guilty to all charges, including second-degree murder and weapons-related offences.

Much of what is expected at the state trial – the prosecutor's case, Mangione's defence, and obstacles both parties face – were previewed in months of court filings and arguments, but some questions remain unanswered.

One of the most crucial elements of the Mangione case was decided earlier this summer, after a multi-day hearing in December where the judge weighed which evidence prosecutors could present during trial.

Mangione's team mounted an aggressive bid to exclude evidence recovered from his Pennsylvania arrest. It alleged that state police improperly seized and searched Mangione's possessions, and did not properly advise him of his constitutional rights before questioning him.

The defence succeeded in excluding some items - a gun magazine, cell phone, passport, wallet and computer chip, found in Mangione's backpack.

But Judge Gregory Carro allowed at trial a gun and notebook with Mangione's purported writings, viewed as vital to the prosecution.

Prosecutors have unveiled surveillance footage showing the moment Thompson was shot from behind by a hooded individual. They also used footage to piece together Mangione's alleged movements after the shooting, and ballistics and fingerprint evidence they claim bolsters their case.

As trial approaches, Mangione's team has yet to unveil its full strategy. So far, his lawyers have not offered a robust alternative theory to the one prosecutors have put forth.

"We do not have, like in 'The Fugitive,' the idea of the one-armed man who's the real killer," said former federal prosecutor Mitchell Epner, referencing a 1993 thriller about a man wrongly convicted of killing his wife.

Earlier this summer, Mangione's lawyers proposed, then quickly withdrew, an "extreme emotional disturbance" argument.

In such a defence, New York law requires lawyers to show a defendant "acted under the influence of extreme emotional disturbance for which there was a reasonable explanation or excuse". Extreme emotional disturbance would allow the jury to consider the less severe charge of manslaughter, rather than second-degree murder. But jurors would have to be convinced of the accused's state of mind at the time.

Some experts wondered if Mangione would argue a full insanity plea - different from emotional disturbance, but his lawyers have not proposed it.

"Short of being delusional, or having no understanding of the nature of what one is doing, an insanity defence is not likely to be successful," said Cheryl Bader, who leads the Criminal Defence Clinic at the Fordham University School of Law.

Mangione's team did not immediately respond to a request for comment.

As in every US criminal trial, the burden rests on the prosecution to prove its case to the jury beyond a reasonable doubt, a high legal bar.

"The more his case is about the question of who killed the victim, the easier it is for the prosecution," said Epner.

Epner cited other themes, including healthcare in America, as potential narrative threads that could sway a jury in Mangione's favour.

"The more it's about the other peripheral issues, the harder it is for the prosecution," he said.

That question, which will have to be sorted out before the trial, could determine if the proceedings evolve into a massive spectacle across traditional outlets, social media, and streaming platforms.

In recent weeks, Mangione's lawyers questioned procedures for admitting journalists in court and why an overflow room allowing more people to watch the trial hadn't been arranged.

The defence also requested that the trial be "broadcast live", though New York state courts do not allow public live streams.

In a letter to Carro, prosecutors have said they have "no role in developing" media procedures at trial and "will have no role in selecting which news reporters attend the trial".

In a new filing on Monday night, the Manhattan district attorney's office said it would "defer to the court's judgement" on courtroom access. But the DA cautioned that adequate security was needed to prevent spectators from covertly recording the trial from an overflow room in violation of New York law.

While the public can be admitted to court in New York, space is often limited at high-profile trials. The court and its communications office were "actively finalising the plan for the upcoming trial, including arrangement for an overflow room," according to spokesman Al Baker.

"We remain firmly committed to providing the greatest possible access for both the media and the public," he said, adding that the court is "evaluating the complex logistical and safety considerations involved".