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.

Donald Trump's Mar-a-Lago Club was worth more than $1.2 billion in 2021 -- roughly double the value listed in Trump's statement of financial condition -- according to defense expert Lawrence Moens.

Describing Mar-a-Lago as a castle nestled on 17.6 acres of waterfront property, Moens said he determined the value by considering nearby properties and adding the total value of the club's 500 memberships, which in 2021 cost $350,000 each.

Between 2011 and 2021, Moens' analysis found that Trump undervalued Mar-a-Lago in his statements of financial condition -- but his analysis appeared to be based on Trump being able to sell the property to an individual to use it as a private residence, which the New York attorney general says Trump is prohibited from doing based on a 2002 deed he signed that would "forever extinguish their right to develop or use the Property for any purpose other than club use."

Judge Engoron only qualified Moens as an expert on the value of residential real estate.

Moens spoke with confidence about his ability to value real estate in Palm Beach, saying that he has sold billions of dollars of real estate since his first sale as a broker in 1982. Asked if any broker has sold more Palm Beach real estate than he has, Moens replied, "They don't exist."

"I am on the front lines everyday of selling properties, and I have a pretty good handle of what is going on currently in the market," Moens said. He later added, "My numbers are usually right."

Moens also put together a seven-minute promotional video about Mar-a-Lago, which was played during his testimony. Set to relaxing music, the video included high-resolution drone shots and dramatic panning shots of the property's amenities. After the video played, Moens highlighted details such as hand-carved stones, gold decorations that cost millions to construct, and other details that required years of work from tradesmen.

"I invited the attorney general's office to come see it anytime. The offer still stands," Moens said. "I will make sure he is not there when you come," he said of Trump.

Engoron appeared attentive to Moen's testimony -- but once Moens left the courtroom, he indicated that he wasn't as concerned about Mar-a-Lago's specific value as he was about whether it was misrepresented.

"I see this case about the documents -- whether the defendants used false documents when transacting business," Engoron said. "I am not trying to figure out what the value is ... I don't necessarily consider it relevant."