The 77-year-old Republican is due to take the stand at 10:00 am (1500 GMT), sitting next to Arthur Engoron, the judge overseeing the case whom Trump has repeatedly derided as "unhinged" and a "Trump-hating radical left, Democrat operative."

Engoron has responded by slapping Trump with two fines -- one for $5,000, another for $10,000 -- when he ruled the onetime reality television star had violated a partial gag order imposed after he bashed the judge's clerk on social media.

Beneath the Manhattan courtroom's fading mural acclaiming the 1683 adoption of a "Charter of Liberties," Trump is to be sworn in and questioned, as did his two eldest sons Don Jr. and Eric the week before.