When Donald Trump enters a New York courtroom on Tuesday, he’ll face a seasoned judge who is no stranger to the former president’s orbit: Acting New York Supreme Court Judge Juan Merchan.

He has sentenced Trump’s close confident Allen Weisselberg to prison, presided over the Trump Organization tax fraud trial and overseen former adviser Steve Bannon’s criminal fraud case.

But Trump’s historic arraignment on Tuesday will perhaps be Merchan’s most high-profile case to date, even after a long career atop the state-level trial court.

Merchan has been described by observers as a “tough” judge, yet one who is fair, no matter who is before him.

Here are key things to know about the judge:

“A man of his word”: Trump is already fanning the flames on social media with his views on Merchan and his indictment. But attorneys who have appeared before him told CNN that the judge doesn’t stand for disruptions or delays.

Judge Merchan “was clear in signaling his judicial inclinations, which helped me tremendously in giving Mr. Weisselberg informed legal advice. Judge Merchan was always well-prepared, accessible, and – most importantly in the Weisselberg matter – a man of his word. He treated me and my colleagues with the utmost respect, both in open court and behind closed doors,” Nicholas Gravante, the attorney who represented Weisselberg in his plea, said via email.

“Tough” but “compassionate”: Merchan showed some of his tough side when Weisselberg was sentenced, telling the former Trump associate that if he had not already promised him a five-month sentence, he would have handed him a “much greater” sentence after having listened to evidence at trial.

In addition to the Trump cases, Merchan also handed a 25-years-to-life sentence to a Senegalese man who raped and murdered his girlfriend.

Trump attorney Timothy Parlatore said during an interview Friday on CNN that Merchan was “not easy” on him when he tried a case before him, but echoed that the judge likely will be fair.

Merchan, however, is also credited by his peers for having helped create the Manhattan Mental Health Court, which he often presides over and where he has earned a reputation for “compassionate” rulings that give defendants second chances.

Still, Earl Ward, a trial attorney and chair of public defender nonprofit The Bronx Defenders, said that having watched Merchan preside over cases in the Mental Health Court, the judge often sided with prosecutors.

His background: Born in Bogotá, Colombia, Merchan emigrated to the United States at the age of 6 and grew up in the New York City neighborhood of Jackson Heights, Queens, according to a New York Times profile of the judge. He was the first in his family to go to college. He received his law degree from Hofstra University.

Merchan launched his legal career in 1994 as an assistant district attorney in the trial division in the Manhattan District Attorney’s Office. Several years later, he moved on to the state attorney general’s office, where he worked on cases in Long Island. In 2006, New York Mayor Michael Bloomberg, then a Republican, appointed Merchan to Family Court in the Bronx, and Democratic Gov. David Paterson appointed him to the New York State Court of Claims in 2009 — the same year he began serving as an acting New York Supreme Court Judge.

CNN’s Kara Scannell and Lauren del Valle contributed to reporting in the post.