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.

Ivanka Trump must appear to testify at her father’s fraud trial, Judge Arthur Engoron decided from the bench Friday morning.

“I want to see her in person. That is how we prefer testimony,” Engoron said after denying Ivanka Trump’s motion to quash the trial subpoenas she was served.

While Ivanka Trump was not in attendance at Friday's hearing, her lawyer Bennet Moskowitz argued that the state’s justification for bringing Ivanka to the courtroom “falls on its face.”

Characterizing the state’s argument as “a bridge too far,” Moskowitz reiterated that Ivanka neither lives nor has done business in New York since 2017.

State attorney Kevin Wallace defended the subpoenas by arguing Ivanka Trump was a former Trump Organization executive who was the main contact with lenders for Trump’s Washington D.C. Old Post Office hotel. Wallace added that Ivanka Trump still owns properties in New York and operates business here.

Ruling from the bench after a short break, Engoron found that the state presented sufficient evidence to prove that Ivanka does business in New York.

“Ms. Trump owns property in New York and has done business in New York,” he said.

Engoron added that her testimony should not be scheduled before next Wednesday to allow her lawyers to appeal his ruling.

“A trial is a search for the truth, and the law is entitled to every person’s evidence,” Engoron said.