▶ Watch Video: Manhattan district attorney looks into Trump alleged “hush money” payment

An attorney may be called before a Manhattan grand jury on Monday to discredit star witness Michael Cohen in the investigation into former President Donald Trump, two sources confirmed to CBS News. 

Cohen, Trump’s former personal attorney, has been asked to be available if needed before the grand jury, which is investigating an alleged “hush money” payment Cohen made to adult film star Stormy Daniels ahead of the 2016 election, according to two people familiar with the matter.

Cohen has been asked to be in close proximity to the grand jury, which meets in Lower Manhattan, in case he’s needed to “rebut” another witness expected to testify Monday.

Two sources told CBS News that attorney Robert Costello, who worked as a legal adviser to Cohen before they had a falling out, may appear before the grand jury to discredit Cohen, a key witness in the investigation into Trump. Costello has been asked to appear by Trump’s attorneys, sources said, but it’s unclear if he will actually be called. 

Former Trump lawyer Michael Cohen leaves after testifying before grand jury in Manhattan, New York City on March 15, 2023.

Fatih Aktas/Anadolu Agency via Getty Images

Costello’s possible appearance was first reported by The New York Times

Trump posted on social media on Saturday that he expects to be arrested on Tuesday by Manhattan District Attorney Alvin Bragg. He did not post any details about what he could be charged with, but Bragg’s office has been conducting an investigation into the $130,000 Cohen paid Daniels ahead of the 2016 election. The president also called on his followers to “PROTEST, TAKE OUR NATION BACK!” in the event of his arrest.

Earlier this month Trump was invited to testify before the grand jury, a step that often signals an upcoming indictment. Joe Tacopina, an attorney for Trump, said the former president will not accept the invitation to appear.

Trump’s attorney on Saturday said his social media comments were related to news reports. “Since this is a political prosecution, the District Attorney’s office has engaged in a practice of leaking everything to the press, rather than communicating with President Trump’s attorneys as would be done in a normal case,” Trump attorney Susan Necheles said in a text to CBS News.

Bragg has not commented on Trump’s social media posts. But in a memo to staff on Saturday, Bragg warned of potential threats and said “your safety is our top priority.”

“We have full confidence in our outstanding security staff and investigators, along with our great OCA and NYPD colleagues, and will continue to coordinate with all of them,” Bragg said in a memo. “We do not tolerate attempts to intimidate our office or threaten the rule of law in New York. Our law enforcement partners will ensure that any specific or credible threats against the office will be fully investigated and that the proper safeguards are in place so all 1,600 of us have a secure work environment.”

Cohen, a central figure in Bragg’s investigation, testified before the grand jury last week. He reported to prison in May 2019 on federal charges related to the payout as well as charges of tax evasion and lying to Congress. 

Trump has denied any wrongdoing, including ever having a sexual relationship with Daniels. He has called the case “a political Witch-Hunt” and an “old, and rebuked case, which has been rejected by every prosecutor’s office.”

Caroline Linton contributed to this report.