Monday saw Robert Costello, a one-time adviser to Michael Cohen, testify in former President Donald Trump's New York hush-money trial.

Yet according to Newsweek, his behavior on the stand led to an angry outburst from Judge Juan Merchan.  

Judge lectures Costello on "decorum in my courtroom"

The magazine cited reporting from correspondent Katherine Fung, who said Costello at one point reacted to a sustained objection by exclaiming "Jeez!"

An annoyed Merchan is said to have responded by saying, "I'm sorry?" The judge grew further irritated when Costello began blowing "raspberries'' after Merchan sustained additional objections.

"Mr. Costello... I'd like to discuss proper decorum in my courtroom," an angry Merchan was quoted as saying to Costello.

"As a witness on the stand, if you don't like my ruling, you don't say 'jeez!' and then you don't say, 'strike it' because I'm the only one who can strike testimony in the court. If you don't like my ruling, you don't give my side eye or roll your eyes," he continued.

Fung said that Merchan then "erupted" and demanded to know if the witness was "staring me down." He then ordered that members of the media leave the courtroom.

Costello accused Cohen of lying on witness stand

The reporter noted how Costello earlier testified that "Michael Cohen said numerous times that President Trump knew nothing" about payments to adult film star Stormy Daniels.

Trump's trial was not the only venue in which Costello has discussed Cohen, as the Washington Examiner reported that he also did so when testifying on Capitol Hill this past Wednesday.

A lawyer who once worked for Michael Cohen accused him on Wednesday of perjuring himself while testifying this week during former President Donald Trump’s hush money trial.

Bob Costello, a longtime criminal defense attorney, said that when Cohen took the stand and accused… pic.twitter.com/ScedAzbFPk

— Washington Examiner (@dcexaminer) May 15, 2024

"I read Michael Cohen’s testimony from yesterday's trial in New York on the way down on the train, and virtually every statement he made about me is another lie," Costello told lawmakers.

Law professor calls Costello a "kill shot witness"

Costello maintained that Cohen was desperate to avoid being incarcerated, at one point telling him, "I will do whatever the F I have to do. I will never spend one day in jail."

During an appearance on Fox News, George Washington University Law School professor Jonathan Turley described Costello as a "kill shot witness."

Costello spoke of how Cohen told him "numerous times" he had no incriminating information regarding Trump, saying, "I swear to God Bob, I don't have anything on Donald Trump."