It marks the first time that a US president - former or current - has faced a criminal trial
Both legal teams are haggling over evidence that can be used in trial, and will soon shift their focus to selecting the jury
Trump is accused of trying to cover up a $130,000 hush-money payment to porn star Stormy Daniels ahead of the 2016 election - which he won
Daniels claims she and Trump had sex in 2006, and she was then paid by Trump's then-lawyer Michael Cohen to stay quiet about it
Trump is accused of falsifying his business records by saying the reimbursement money he gave Cohen was for legal fees
He faces 34 counts of fraud, but denies any legal wrongdoing - and also denies having an affair with Daniels
The maximum penalty if Trump is found guilty is four years behind bars, but experts say a much less severe penalty would be more likely
A tale of two cities: Anti- and pro-Trump protesters stand guard outside
John Sudworth
Reporting from outside court
As we wait for the lunch break to finish, let's take a look at the scene outside the Manhattan courthouse.
The police have divided the park outside into two sections. One side for the pro-Trump group, while the other is designated for anti-Trump supporters.
The atmosphere is, in the main, good natured, but every now and then the odd protester or two tries to sneak into the wrong section.
One woman, holding up a number of signs including one that says, "We believe Stormy Daniels", was quickly surrounded by a heated MAGA-hatted crowd, shouting "lock her up!" and "Soros provocateur!".
She was then escorted back into the pro-Trump section by New York police officers.
Prosecutors want Trump to be fined $3,000 over gag order
Let's take a look at one of the courtroom skirmishes that happened just before lunch.
Prosecutors called for Trump to be fined $3,000 (£2,400) for allegedly violating the gag order imposed on him three times.
Justice Merchan imposed the order barring Trump from making public comments about those related to the case, including potential witnesses and the judge's family.
Defence attorney Todd Blanche argued the three social media posts prosecutors pointed to did not violate the gag order.
“He is responding to salacious, repeated, vehement attacks by these witnesses,” Blanche said.
Justice Merchan did not immediately issue a ruling, so we will find out his thoughts on the matter after the lunch break.
Watch live at BBC.