Donald Trump's motorcade has arrived at the New York State Supreme Courthouse in lower Manhattan.

Court is scheduled to get underway at 10 a.m. ET, with Trump scheduled as the day's only witness.

Donald Trump, in New York, had a prep session with his lawyers Sunday ahead his testimony, sources tell ABC News.

Trump's mood during the session fluctuated between fits of anger regarding the case and being "in a good head space," according to sources.

The former president "can be a good witness if he stays focused," one source said.

Former President Trump is due in court to begin his testimony in his $250 million civil fraud trial at 10 a.m. ET.

Hundreds of members of the news media are huddled outside the New York State Supreme Courthouse ahead of Trump's arrival, with some having waited overnight.

After multiple in-court disputes about communications between him and his law clerk, Judge Arthur Engoron modified his limited gag order to cover attorneys in former President Donald Trump's civil fraud trial.

"Defendants may reference my staff as is appropriate to ask about scheduling issues or the management of the trial, which is an integral part of their jobs. What they may not do is to make any further statements about internal and confidential communications (be it conversations, note passing, or anything similar) between me and my staff," Engoron wrote in his supplemental limited gag order on Friday.

Engoron wrote that defense lawyers Chris Kise, Alina Habba, and Clifford Robert made "repeated, inappropriate remarks about my Principal Law Clerk, falsely accusing her of bias against them and of improperly influencing the ongoing bench trial."

The attorneys have raised multiple arguments during the trial that Engoron and his clerk passing notes between each other suggests impropriety and is distracting. Going forward, if the lawyers want to object to communications with his clerk, Engoron advised that they refer to the order as a "blanket statement."

"This gag order is as narrowly tailored as possible to accomplish its purpose, which is to protect the safety of my staff and promote the orderly progression of this trial," Engoron said.

To justify the safety threat, Engoron added that his chambers has received "hundreds of harassing and threatening phone calls, voicemails, emails, letters, and packages" since the start of the trial,

The judge threatened "serious sanctions" for violations of the extended order.

House Intelligence Committee Chair Rep. Michael Turner and House GOP Conference Chair Rep. Elise Stefanik have requested that the Department of Justice investigate Michael Cohen for perjury following his testimony in the trial last month.

During his trial testimony, Cohen said that he lied to the House Permanent Select Committee on Intelligence in 2019 when he said that Donald Trump and Allen Weisselberg did not ask him to inflate Trump's personal statement.

"So, you lied under oath in February of 2019? Is that your testimony?" defense attorney Alina Habba asked in court.

"Yes," Cohen responded.

Shown his 2019 testimony in court, Cohen subsequently reversed himself and said that his 2019 testimony was truthful, explaining the contradiction by clarifying that Trump speaks like a "mob boss" and that he indirectly asked for his statement to be inflated.

In a letter to Attorney General Merrick Garland sent today, Stefanik and Turner requested that the Department of Justice open an investigation into Cohen potentially committing perjury.

"That Mr. Cohen was willing to openly and brazenly state at trial that he lied to Congress on this specific issue is startling," they wrote. "His willingness to make such a statement alone should necessitate an investigation."

Last week, Stefanik sent a separate judicial complaint to the New York State Commission on Judicial Conduct related to the conduct of the judge overseeing Trump's trial. In a statement to ABC News, a court representative said in response that the judge's actions "speak for themselves."