A trial has begun in the case of a former US Marine who is accused of putting a homeless man in a fatal chokehold on a New York subway train.

Daniel Penny, 25, has pleaded not guilty to charges of second-degree manslaughter and negligent homicide.

Witnesses said Jordan Neely, a 30-year-old black man, was shouting at other subway passengers and asking for money when Mr Penny, who is white, pinned him down for several minutes, eventually killing him.

The May 2023 event quickly became a political flashpoint, with conservatives praising Mr Penny as a hero, and critics including civil rights activists saying he acted as an unjustified vigilante.

A crowd of about 40 people protesting over Mr Neely’s death gathered outside the court house in New York ahead of the start of jury selection on Monday.

Mr Penny, who has been free on bail since he was charged, came into Manhattan Criminal Court on Monday wearing a blue suit. He stared straight ahead as he walked to sit next to his lawyers.

New York Judge Maxwell Wiley said the first few days of jury selection would involve picking Manhattan residents who are able to sit on a trial that is expected to last six weeks. The voir dire process of jury selection – when prospective jurors are asked questions about their background and potential biases – is expected to begin Friday.

Mr Penny, who has said he was acting in self-defence, faces up to 15 years in prison if convicted of the manslaughter charge.

Prosecutors say he put Mr Neely in a chokehold “that lasted approximately six minutes and continued well past the point at which Mr Neely had stopped purposeful movement”.

Fellow passengers filmed the incident, with a freelance journalist recording Mr Penny holding Mr Neely around the neck for several minutes.

Witnesses said Mr Neely was shouting about being hungry and willing to return to jail or die, but there was no indication he physically attacked anyone.

Emergency responders could not resuscitate him and Mr Neely was pronounced dead at hospital.

The city medical examiner ruled his death a homicide, caused by compression of the neck.

Mr Neely was a Michael Jackson impersonator who performed in Times Square and was known throughout the city.

He had dozens of previous arrests on charges such as evading fares, theft and assaults on three women.

Family members say he had mental health issues that began more than 15 years earlier, when his mother was strangled to death by her boyfriend.

Mr Penny, a Long Island native who served in the Marines, wrote on social media that he did not intend to kill Mr Neely.

“I was scared for myself but I looked around there were women and children, he was yelling in their faces saying these threats. I just couldn’t sit still,” he wrote.

There has been a growing awareness of the danger of chokeholds after the 2014 death of Eric Garner, an unarmed man from New York City who police restrained by the neck. Afterwards, the state banned police from using chokeholds during arrests. It then went further to include sitting, standing or kneeling on a person’s back or diaphragm following George Floyd’s death in Minneapolis in 2020.