During a critical period in 2018, Costello consulted with Michael Cohen, Trump’s former fixer. Now, as a witness for the defense, Costello had one primary purpose: undermine Cohen’s credibility. Costello did appear to score some points on that front, though his churlishness in court — while clearly pleasing Trump — may have diminished the effectiveness of his testimony.

Cohen, the prosecution’s star witness, ended his three-and-a-half days of testimony earlier on Monday, just before prosecutors rested. He reiterated the account that he told several times last week: Trump, he said, instructed him to pay $130,000 to silence porn star Stormy Daniels and then approved a scheme to falsify records related to the payment.

But Costello testified that Cohen told him the opposite in 2018, shortly after the Daniels hush money came to public light and the FBI raided Cohen’s home and office. According to Costello, Cohen repeatedly and unequivocally declared in a private meeting and phone calls that Trump knew nothing about the payment to prevent Daniels from going public in the final weeks of the 2016 presidential campaign with her claims of a sexual encounter with Trump a decade earlier.

“Michael Cohen said numerous times that President Trump knew nothing about those payments. That [Cohen] did this on his own. And he repeated that numerous times,” said Costello, who in 2018 was working for Rudy Giuliani and tried to convince Cohen not to flip on Trump.

Costello is well accustomed to portraying Cohen as a serial liar: Just last week, he appeared before a panel of the House Judiciary Committee to take public whacks at Cohen’s credibility.

But perhaps the most noteworthy aspect of Costello’s testimony was his pugnacious and sarcastic delivery — and the reactions it garnered. As jurors looked on, he was combative toward the prosecutors and irreverent to the judge.

At one point, seemingly fed up with prosecutors’ objections, Costello muttered “jeez” and apparently rolled his eyes when Justice Juan Merchan sustained the objections. Merchan sent the jury out of the courtroom so he could give Costello, who is a former federal prosecutor, a stern rebuke.

“If you don’t like my ruling, you don’t say ‘jeez.’ And then you don’t say ‘strike it.’ You don’t give me side eye, and you don’t roll your eyes,” the judge told Costello.

As Merchan was about to call the jury back into the room, he snapped at the defense witness and veteran attorney: “Are you staring me down right now?”

Then, in one of the most dramatic moments of the trial, Merchan briefly ordered journalists and other onlookers to clear the courtroom so the judge could continue to admonish the witness outside the public’s view.

After reporters were ordered out by court by security officers despite numerous verbal protests, Merchan dressed down Costello and Trump’s defense.

“I’m putting you on notice that your conduct is contemptuous,” the judge said to Costello, according to a transcript released Monday evening. “If you try to stare me down one more time, I will remove you from the stand.”

“I will strike his entire testimony; do you understand me?” the judge said to Trump lawyer Emil Bove.

“Can I say something, please?” Costello pleaded.

“No. No. This is not a conversation,” Merchan replied.

After court adjourned for the day, Trump seized on the back-and-forth in his daily remarks to reporters in the courthouse hallway.

“A tyrant,” Trump called the judge.

“You saw what happened to a highly respected lawyer today,” Trump said. “Wow.”

Costello — who at 76 is just a year younger than Trump — seemed eager to joust with the prosecution as a stand-in for Trump. Although the former president has said at several points he would like to testify in his own defense, most legal experts say there’d be little upside in doing so, and on Monday, his lawyers indicated he is not likely to take the stand.

That means Costello, who is expected to return to the stand for further testimony on Tuesday, may be the last witness jurors hear from. With scheduled days off on Wednesday, Friday and Memorial Day next Monday, Merchan said he expects to hold closing arguments on Tuesday, May 28.

After that, the jury will begin deliberating.