"Good morning, Mr Trump."

The innocuous greeting from a New York judge belied the grim expression on Donald Trump's face as he sat flanked by his lawyers in the Manhattan Criminal Courts Monday. 

While his legal team tussled with the prosecution over what evidence could be admitted, the first former US president to face a criminal trial appeared to listen intently and -- barring a few words spoken in response to Judge Juan Merchan -- silently.

The case, which could prove enormously consequential for both Trump and the country, is being heard in courtroom 1530 inside an imposing, scaffolding-clad Art Deco courthouse on New York City's Centre Street.

Trump wore his signature red tie with a white shirt and dark blue suit and a US flag lapel pin as Merchan declared the trial open.

The 45th president fixed the magistrate with a defiant look, having accused him of being "corrupt" on his Truth Social platform after Merchan declined repeated calls from the defense to recuse himself.

"We want justice to be done, that's all we want," said the judge.

The case is scheduled to last up to two months and centers on payments made to former adult film star Stormy Daniels as Trump closed in on his 2016 election win.

'Political persecution'?

Trump did not disrupt proceedings, which were largely technical, as he has done in other cases.

That includes his civil fraud trial, heard in a nearby courthouse, that resulted in a $355 million civil penalty that he is appealing.

Time may be against Trump, who is campaigning to dislodge President Joe Biden from the White House at November polls, as jury selection alone could take up to two weeks. 

More than 100 prospective jurors will be present in court at any one time from a pool of 500.

Trump regularly conferred with the lawyers seated either side of him, shaking his head irritably when prosecutors made comments with which he disagreed.

"It's true," he muttered at one point in response to an audio tape of him boasting about how well he treats women.

However, he did not react when the now-infamous clip of him describing grabbing women by their genitals was played by prosecutors.

According to The New York Times reporter sitting close to Trump, he at times appeared to fall asleep, head drooping.

But before sitting down and crossing his hands at a brown wooden table where his lawyers spread out their files, the presumptive Republican candidate for the 2024 presidential election set the tone for the trial.

This is an "assault on America" and "political persecution," railed the 77-year-old billionaire who could face prison if convicted.

"It's a country that's failing, it's a country that's run by an incompetent man and is very much involved in this case," Trump said. "This is really an attack on a political opponent, that is all it is, so I'm very honored to be here."

Moments later, five photographers were ushered in to capture the unprecedented scene -- a former president seated at the defendant's table.