A dramatic scene erupted at President Trump’s hush-money trial on Monday afternoon when the presiding judge asked the reporters to clear the courtroom so he could reprimand Mr. Trump’s witness, the veteran attorney Robert Costello. 

“Are you staring me down?” the New York Supreme Court justice, Juan Merchan, asked Mr. Costello, his voice shaking with rage. “Clear the courtroom, right now. Clear the courtroom!”

Close to sixty reporters took their belongings and rushed out into the hallway. 

The prosecution had rested its case after Michael Cohen, Mr. Trump’s former personal attorney and current archenemy, finished his testimony earlier on Monday. As its first witness, the defense called Daniel Sitco, a paralegal who works for one of Mr. Trump’s defense attorneys, Todd Blanche. Mr. Sitko introduced a summary chart of phone calls between Cohen and Mr. Costello, an attorney who works for the law firm of Davidoff Hutcher & Citron and attempted to represent Cohen in 2018 after his apartment, office, and the hotel room he was staying in at the time (due to flooding at his apartment) were raided by the FBI, a raid connected to Cohen’s work for Mr. Trump. Mr. Costello served as a conduit between Cohen and the White House when Cohen and Mr. Trump, in the crosshairs of Special Counsel Robert Mueller, were not speaking directly. 

Mr. Costello, who also represented Mayor Giuliani, and Cohen parted on bad terms in 2018, after Cohen felt abandoned by Mr. Trump and decided to turn state’s evidence. Ever since, Mr. Costello has been on a crusade to undermine Cohen’s credibility. He testified on Capitol Hill on Wednesday before the House Select Subcommittee on the Weaponization of the Federal Government where he denounced Cohen as an inveterate liar whose core contention that Mr. Trump personally ordered the hush-money payment to the porn star Stormy Daniels was  false. 

Cohen’s testimony about Trump’s role in the $130,000 hush-money payment to Ms. Daniels, whose real name is Stephanie Clifford, is key to Manhattan District Attorney Alvin Bragg’s case against Mr. Trump. Mr. Bragg has charged with Mr. Trump with ordering Cohen to pay Ms. Clifford to buy her silence about a one-time sexual encounter she claims to have had with Mr. Trump at a celebrity golf tournament at Lake Tahoe in 2006. Mr. Trump denies ever having had sex with Ms. Clifford. Mr. Bragg alleges that Mr. Trump, while president, reimbursed Cohen for the payment and illegally disguised it as “legal expenses” in his bookkeeping.

As Mr. Costello began testifying on Monday, the prosecution began interrupting him with objections. Growing more and more frustrated, as the judge was sustaining the objections, Mr. Costello said, “Jeez.”

The surprised judge snapped at the witness, “I’m sorry? I’m sorry?” 

“Strike it, I’m —” Mr. Costello answered.  

The judge was stunned. Mr. Costello, who used to be a deputy chief of the Criminal Division of the United States Attorney’s Office in the prestigious Southern District of New York, knew that as a witness, he had no authority to strike anything from the record. The judge decides what is stricken and what remains on the record. Judge Merchan educated Mr. Costello, well aware that the witness had attempted to provoke him.  

After Mr. Costello had made another comment under his breath, calling an objection “ridiculous,” Judge Merchan had had enough. He sent the jury out of the room, and then he turned to the witness and said, “Mr. Costello, I want to discuss proper decorum in my courtroom. When there’s a witness on the stand, you don’t say ‘jeez,’ you don’t say ‘strike it,’ and if you don’t like my ruling, you don’t give me the side eye, you don’t roll your eyes.”

That’s when Mr. Costello stared at the judge, who then accused him of “staring me down.” 

The reporters were told to leave the courtroom, and a few minutes later were let back inside. 

Mr. Costello will take on the witness stand again tomorrow to complete the cross-examination by the prosecution.