(Bloomberg) -- The New York judge overseeing Donald Trump’s historic criminal case has had his share of high-profile trials, but the courtroom drama he’ll face with the former president will put him in a whole different league.

“This is going to be an enormous undertaking because of the nature of who the defendant is,” said Cyrus Vance Jr., the former Manhattan District Attorney who preceded current DA Alvin Bragg. “Trump has a history of being difficult to keep him and his organization on track,” Vance said. “It is going to be a really big job.”

That’s already evident. On his Truth Social platform Friday, Trump trashed the judge — New York State Supreme Court Justice Juan Merchan — claiming he “HATES ME” and spelling his name incorrectly in the process. “His name is Juan Manuel Marchan, was hand picked by Bragg & the Prosecutors, & is the same person who ‘railroaded’ my 75 year old former CFO, Allen Weisselberg, to take a ‘plea’ deal,” the former president wrote.

Trump, who in 2016 famously attacked the federal judge in his Trump University civil case as biased because of his Mexican ancestry, has shown no reluctance to criticize judges, who are ethically barred from fighting back. Merchan, born in Colombia, will be in the hot seat in what could be the biggest case ever tried in the Manhattan criminal court.

Merchan has already gotten a taste of cases involving Trumpworld. Starting in January, he oversaw the grand jury that indicted Trump Thursday, after he handled the almost two-month-long tax-fraud trial in which two of Trump’s companies were found guilty of 17 felonies. He also presided over a case in which Weisselberg, Trump’s longtime former chief financial officer, pleaded guilty to his role in a 15-year-long tax-fraud scheme.

Weisselberg got five months in jail, with the judge saying: “The entire case was driven by greed.” He fined the two Trump companies $1.6 million, the maximum penalty.

A court spokesman didn’t immediately respond to a request for comment.

Merchan is also assigned the criminal case against former Trump adviser Steve Bannon on charges he cheated contributors to a privately funded US-Mexico border wall out of more than $15 million.

He’s tended to be conservative regarding access in Trump-related cases, having once held a hearing in the Bannon case without notifying the press or the public. He only released a transcript after his actions provoked complaints from the media. During the tax-fraud trial of two of Trump’s companies, Merchan initially directed that prosecution evidence related to Trump’s businesses, which had been publicly displayed in court, shouldn’t be released to reporters covering the trial. He only relented after the media challenged him.

Merchan began his legal career in 1994 as a Manhattan prosecutor in the same office that has charged Trump. He has been a judge since 2006 and had some cases that were the stuff of tabloid fodder.

In one case, a suburbanite named Anna Gristina became the subject of headlines in 2012 after she was charged with running a $2,000-an-hour escort service for wealthy and powerful men. In the end, she pleaded guilty and got six months. The case was the subject of the 2021 Lifetime movie Soccer Mom Madam.

Proceedings in Merchan’s court can be more volatile than in the federal courthouse a few doors away. As Merchan sentenced a defendant to 13 years in prison for gun possession and reckless endangerment in 2016, the man’s sister had to be locked up for interrupting and threatening the prosecutor, saying, “I’m gonna kill the DA,” according to a report in the New York Daily News.

He sentenced to community service two men who in 2013 parachuted from the Freedom Tower, the skyscraper that replaced the World Trade Center towers. He told them they had “sullied the memories” of the people who died in the 2001 terror attacks. In 2012, he sentenced a Senegalese man who had raped and murdered his former girlfriend to 25 years to life, having ruled earlier that the defendant couldn’t call a “witch doctor” to support his claim that he was under a curse that made him kill.

The courthouse has begun preparing for what could unfold during Trump’s expected arraignment on Tuesday. On Friday afternoon, a section of the floor where Merchan’s courtroom is located was blocked off by a barricade, and guarded by an officer. Reporters were ordered off the floor, with court officers saying it was “off limits” to the public. Earlier in the day, US Secret Service, NYPD and state court officers were seen doing a security sweep.

After beginning his career in the DA’s office, Merchan left to work for the state attorney general. Former mayor Michael Bloomberg appointed him as a Family Court judge in the Bronx in 2006. Bloomberg is the founder and majority owner of Bloomberg LP, which owns Bloomberg News.

Merchan has been an acting justice in the criminal section of Manhattan’s trial-level court, the New York County Supreme Court, since 2009. He’s a graduate of Baruch College and Hofstra University School of Law.

“Judge Merchan is going to want this case tried in the courtroom,” Vance said. “I think it’s wise to keep a very tight rein on the parties and the lawyers themselves, except Merchan can’t control what the public says. What he can in some ways control what the party’s lawyers say and, and impose penalties for violating his order.”

When he says “parties,” does he refer to Trump?

“I do, and good luck with that,” he said.

--With assistance from Hadriana Lowenkron.

(Adds security measures in place in courthouse in paragraph 14)

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