In a sidebar, Trump's attorney told Judge Merchan want to use ex-Cohen attorney Robert Costello to push back on Cohen's claims that he was worried about speaking to Costello because he was worried it would get back to Trump.

"That's not Mr. Costello's recollection," defense attorney Emil Bove said. "To rebut the government's pressure campaign theory -- that's why this evidence is admissible."

Bove told Merchan that Costello would testify that Cohen told him that Trump had no awareness of the Stormy Daniels' hush money payment.

Earlier today, Cohen testified that he lied to Costello about Trump's awareness because he did not trust Costello.

"The whole purpose was to make Mr. Trump sound threatening," Bove said.

"I don't think so," Merchan responded.

Prosecutor Susan Hoffinger argued that defense lawyers did not include Costello on their witness list or provide the exhibits related to his testimony.

"Rebutting the pressure campaign should have been part of their direct case," Hoffinger said.

Merchan called a brief recess to consider the arguments but ordered the parties to remain in the courtroom.

The prosecution objected to the defense calling Robert Costello, Michael Cohen's former attorney to the stand.

Out of earshot of the jury, prosecutor Susan Hoffinger asked Judge Merchan to omit Costello or limit his testimony to two questions.

"I think there's very limited testimony that's permissible here if at all," Hoffinger said.

The defense said it wants to use Costello to rebut Cohen's testimony about a "pressure campaign" carried out against him not to flip on Trump after Cohen made Stormy Daniels payment.

Costello, a longtime Trump ally, testified before the grand jury in March 2023 as an exculpatory witness at the request of Trump's attorneys.

On cross-examination, prosecutor Becky Mangold quizzed defense witness Daniel Sitko about the technical process for putting together the summary chart from cell phone records.

The defense attempted to show through the call summary that Cohen and his then-attorney Robert Costello spoke 75 times. On cross-examination, the defense paralegal conceded it wasn't quite that many.

After Sitko stepped off the witness stand, the defense called Robert Costello himself.

The defense called Daniel Sitko, a paralegal for defense attorney Todd Blanche.

Sitko introduced a summary chart of phone calls between Michael Cohen, his one-time attorney Robert Costello, and the law firm of Davidoff Hutcher & Citron.

Judge Merchan denied a request from defense lawyers to broaden the scope of testimony from their expert witness Bradley Smith, who is an expert on campaign finance regulations.

On Thursday, defense lawyers asked Merchan to allow Smith to testify about various terms related to federal campaign finance laws. Merchan denied the request, citing long standing precedent prohibiting witness testimony about the law.

"An expert is not permitted to present or interpret the law," Merchan said.

Merchan also expressed concerns about Smith's testimony prompting a "battle of the experts" between Smith and an expert called by prosecutors, which Merchan said would confuse the jury.

Merchan said that Smith could still testify, as long as he follows the limits imposed in his pretrial ruling on the case's motions in limine.

"The court will monitor this testimony closely to ensure full compliance," Merchan said in a pretrial ruling. "Any deviation from this ruling could result in sanction up to and including striking the expert's entire testimony."

Trump, sitting at the defense table, shook his head after the judge announced his ruling.