Seeking to painting a picture of the machinations behind what Michael Cohen called a "pressure campaign" to keep him in the Trump fold as investigators closed in on him, prosecutor Susan Hoffinger displayed an email from Michael Cohen's then-legal adviser Robert Costello to Costello's law partner in which Costello wrote that Cohen "continues to slow play us and the president -- is he totally nuts???"

"I am in a golf tournament tomorrow early and again on Sunday. What should I say to this a------ ? He is playing with the most powerful man on the planet," Costello wrote.

"That email certainly speaks for itself, does it not, Mr. Costello?" Hoffiner asked.

"Yes it does," Costello said.

Costello insisted that he was not working to advance Trump's interests and denied the suggestion that he "lost control" of Cohen.

Prosecutors displayed an email from Michael Cohen's then-legal adviser Robert Costello to Costello's law partner Jeffrey Citron from Aug. 8, 2018, in which Costello shared a link to a Fox News story about Rudy Giuliani joining Trump's legal team.

"All the more reason for Cohen to hire me because of my connection to Giuliani, which I mentioned to him in our meeting," he wrote.

In another email, Costello said, "Our issue is to get Cohen on the right page without giving him the appearance that we are following instructions from Giuliani or the President. In my opinion this is the clear correct strategy."

Questioned on the witness stand about that email, Costello told prosecutor Susan Hoffinger that he wanted "to get everybody on the same page because Michael Cohen had been complaining incessantly that Rudy Giuliani was making statements in the press that Michael Cohen didn't approve of."

Costello told Hoffinger he has other emails clarifying that, "which I'd be delighted to tell you."

"That's all right," Hoffinger replied snarkily.

The gallery laughed, prompting a court officer to yell, "Quiet!"

Only a few minutes into prosecutor Susan Hoffinger's cross-examination of Michael Cohen's former legal adviser Robert Costello, their exchanges are already sounding tense.

Hoffinger attempted to confirm that Costello boasted about his relationship with Rudy Giuliani, but Costello denied he did so during his first meeting with Cohen.

"You are quoting from an email that is much later," Costello said.

"I am not quoting from an email," Hoffinger replied.

Hoffinger then asked Costello about his relationship with Giuliani.

"He's been to your wedding?" Hoffinger asked.

"Yes he was," Costello said.

“Let’s get the witness please,” Judge Juan Merchan said after taking the bench.

Michael Cohen's one-time legal adviser Robert Costello entered the courtroom and took the witness stand to continue his cross-examination.

“Good Morning, Mr. Costello. Welcome back,” Judge Merchan said.

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.