Prosecutors introduced a new name at Donald J. Trump’s criminal trial on Tuesday: Robert J. Costello.
Mr. Costello is a lawyer who once advised Michael D. Cohen, Mr. Trump’s former fixer and the prosecution’s star witness, acting as his back channel to Mr. Trump and the White House in 2018.
This role, which came by dint of Mr. Costello’s close ties to Mr. Trump’s legal team at the time, was mostly informal. Mr. Cohen never officially retained Mr. Costello or paid him a cent. But the prosecution spotlighted their communications to emphasize Mr. Trump’s broad influence over Mr. Cohen.
At the time that Mr. Cohen and Mr. Costello were speaking, Mr. Cohen was the target of a federal investigation partly related to the hush-money payment to a porn star at issue in the current state case. Mr. Cohen paid off the woman, Stormy Daniels, to silence her story of a sexual encounter with Mr. Trump.
After the F.B.I. searched Mr. Cohen’s home and office in April 2018, Mr. Trump phoned him with an encouraging message, Mr. Cohen recounted on the stand Tuesday. And once Mr. Trump stopped calling, Mr. Cohen felt that Mr. Costello became his messenger, delivering implicit instructions to, in the former fixer’s words, “stay in the fold, don’t flip, don’t speak.”
Mr. Costello has said that he never told Mr. Cohen to keep quiet. Instead, he has said, he was merely relaying messages from Mr. Trump’s legal team, including Rudolph W. Giuliani, the former New York mayor who was close to Mr. Costello. (Mr. Costello later represented Mr. Giuliani in criminal and congressional investigations.)
In one email to Mr. Cohen, Mr. Costello wrote, “Sleep well tonight, you have friends in high places.”
In the end, no one remained friends, and much of the tension stemmed from money.
Mr. Costello and Mr. Cohen had a falling out, partly over unpaid legal bills. Last year, Mr. Costello testified before the grand jury that ultimately indicted Mr. Trump, seeking to undercut Mr. Cohen’s credibility.
Mr. Costello also sued Mr. Giuliani over delinquent bills.
And when Mr. Trump stopped paying Mr. Cohen’s legal fees, their relationship imploded as well. Mr. Cohen vowed to turn on Mr. Trump, a promise he is now fulfilling on the stand.
