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.

After claiming a net worth of $8 billion, Donald Trump declined to share his financial statements with bankers related to his $1 billion bid to purchase the Buffalo Bills football team in 2014, according to documents presented at trial and testimony from Morgan Stanley executive K. Don Cornwell.

Of the 86 parties contacted to potentially bid on the Bills, Trump was one of six parties to make a final bid, according to a Morgan Stanley document shown at trial.

However, when Morgan Stanley attempted a close review of Trump's bid, Trump declined to provide his financial statements.

"We feel it is premature to sign the consent release forms until such time as we know that Mr. Trump is the final bidder," then-Trump attorney Michael Cohen said in a 2014 email shown at trial.

During a management presentation with Bills' leadership, Trump instead handed out a Forbes magazine list to support his bid, according to Cornwell.

"He gave us handouts of the Forbes list of the top-paid entertainers," Cornwell said.

Trump eventually lost his bid to purchase the football team to billionaire Terry Pegula, who outbid Trump by $400 million.

During cross-examination, Cornwell acknowledged that a lawsuit Trump previously brought against the NFL, as well as his affiliation with casinos, also limited the likelihood of his success.

"You thought that President Trump had little chance of being approved by the NFL?" defense attorney Ivan Feris asked.

"Yes," Cornwell replied.

Trump's lawyers have argued that his bid to purchase the Bills -- which has featured prominently in the testimony of other witnesses -- is irrelevant to the conduct alleged in the attorney general's lawsuit.

"It is the defense position that none of this relates to a cause of action in this case," Feris said.