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.

Before stepping down from the witness stand at the end of the afternoon, Donald Trump Jr. was asked repeatedly about his involvement in the Trump Organization's statements of financial condition -- the allegedly fraudulent documents that underpin the attorney general's case.

Trump Jr., who signed and certified the accuracy of the statements while his father was president between 2016 and 2021, said that he was not involved in preparing the filings.

"I wasn't involved in the compilation of this statement of financial condition," Trump Jr. said, placing the responsibility on his accountants.

"Did you work on the statement of financial condition for June 30, 2017?" state attorney Colleen Faherty asked.

"I did not. The accountants worked on it. That's what we paid them to do," Trump Jr. said.

Throughout the afternoon, the tone of the proceedings alternated rapidly between lighthearted and heated, varying from playful interactions between Trump Jr. and Judge Engoron, to bitter spats between some of the lawyers.

"I know you don't like it when good evidence comes in," Faherty told the defense lawyers during one particularly heated exchange.

"There's no reason to raise your voice," Donald Trump Jr.'s lawyer, Clifford Robert, responded.

Trump Jr. is scheduled to return to the stand tomorrow morning.