Who is Robert Costello, the Trump witness accused of staring down judge?

All eyes turned to Robert Costello on Monday after he was called to the witness stand in former President Trump's hush money trial and was quickly admonished by the judge for his courtroom behavior.

Minutes after Costello, a former legal adviser to ex-Trump fixer Michael Cohen, took the witness stand Monday, Judge Juan Merchan asked the jurors to leave the courtroom so he could admonish Costello over his behavior on the stand.

Costello and Merchan shared a tense exchange, and reporters were abruptly asked to leave the courtroom. At one point, Merchan demanded to know if he was being stared down by Costello.

The jury and reporters were permitted back inside minutes later without explanation, and Trump's legal team began questioning Costello.

Costello is a former federal prosecutor turned defense lawyer who spent decades in New York's legal sphere. In 2018, Costello briefly served as an adviser to Cohen as federal prosecutors criminally investigated him and his work on Trump's behalf.

Costello allegedly offered to set up a back channel between Trump and Cohen via former New York City Mayor Rudy Giuliani, who had just joined Trump's legal team.

Taking the stand last week, Cohen told a New York jury that Costello continued to pressure Cohen with "constant calls" and lengthy emails. Costello was apparently angry when Cohen told him he was speaking to a boutique law firm instead, Cohen testified.

Cohen referred to this as a "pressure campaign" from Costello and other Trump allies to remain loyal to the former president amid the FBI investigation. 

“This was part of the pressure campaign,” Cohen said, “that anyone is lying to you, that you are still regarded, the president still supports you, do not speak, do not listen to what any of the journalists” are saying.

"Don't flip. Don't speak. Don't cooperate," Cohen added.

Following the back-and-forth between Costello and Cohen, the two had a falling out, partly due to alleged outstanding legal bills. 

Costello and the law firm Davidoff Hutcher & Citron also sued Giuliani last year for an outstanding legal bill balance of more than $1.3 million.

Costello and the firm served as Giuliani’s representation on numerous occasions, including during the investigations by both Congress and special counsel Jack Smith into the Jan. 6, 2021, Capitol riot, as well as by Fulton County, Ga., District Attorney Fani Willis into an alleged scheme to overturn Georgia’s election results. 

Smith and Willis have since brought two separate election interference cases against Trump and some of his allies.