In the first two days, Judge Juan Merchan has kept proceedings moving at a clip, overseeing the selection of a third of the jury and alternates despite suggestions that screening could take weeks, while putting former president Trump in his place when he appeared to step out of line.
Merchan has said he wants opening arguments to start as soon as Monday, prompting the Republican presidential contender to accuse the judge of "rushing this trial."
"Judge Merchan is a no-nonsense judge who does not tolerate disruption or delay," said Columbia Law School professor John Coffee.
Merchan was born in the Colombian capital Bogota, moving to the heavily Latino Queens borough of New York City at age six.
He worked as a dishwasher and hotel manager at night while in university, which he was the first of six siblings to attend.
In 1990 he graduated from Baruch College and four years later received a law degree from Long Island's Hofstra University, where 97 percent of first-year students receive financial aid.
Merchan went on to work in the Manhattan district attorney's office before being appointed a family court judge in 2006.
Merchan -- who oversaw the 2022 trial of the Trump Organization for tax fraud, imposing a $1.6 million fine on the group -- is also something of a stickler for timekeeping.
Early on this week, he chided Trump's legal team for returning late from a break.
- 'Perfect temperament' -
The judge, along with an appellate court, has repeatedly rebuffed Trump's lawyers as they have sought delays or the relocation of the trial to a different court.
"Merchan has the perfect temperament for presiding over a trial with immense publicity and a defendant who will be testing the judge's patience," said former judge Barry Kamins.
In this case, he has adopted a no-nonsense approach to protecting jurors from the threat of outside interference and intimidation, granting them strict anonymity.
"A protective order is necessary," he wrote ahead of jury selection. "There is a likelihood of bribery, jury tampering, or of physical injury or harassment of jurors."
On Tuesday he scolded Trump to his face for the first time after the defendant was muttering loud enough to be heard by prospective jurors and gesturing animatedly.
"I will not have any jurors intimidated in this courtroom," Merchan said, instructing Trump's lawyers to speak to their client about his behavior.
Trump has accused Merchan of bias, insisting that because of a small donation to the Democratic Party and the judge's daughter working at a campaigning company linked to his opponents, he cannot get a fair trial.
The former president's outbursts saw Merchan impose a gag order barring Trump from publicly disparaging jurors and court staff, which he later expanded to include his own family and that of the lead prosecutor.
But Trump -- accused in this case of covering up hush money payments to a porn star with whom he allegedly had a tryst, to protect his 2016 presidential campaign -- has kept up his criticisms.
"We think we have a very conflicted, highly conflicted judge who shouldn't be on the case," Trump said outside the courtroom Tuesday.
Merchan has agreed to the prosecution's request for a hearing next week to consider whether Trump is already in contempt of court, a charge which could carry prison time for the ex-president if he is convicted.
But law professor Coffee suggested that the Secret Service, charged with protecting Trump, would be unlikely to agree to Trump being imprisoned.
"(Merchan) will make the trains run on time, but this will not much affect Trump's out-of-court statements to the media," Coffee said.
After a day off Wednesday, the trial picks back up on Thursday.
