Senior Enforcement Counsel Kevin Wallace of the New York attorney general's office will lead the direct examination of Donald Trump when the former president takes the stand this morning.

Wallace led the depositions of Trump during the New York attorney general's investigation and also delivered the state's opening statement in the trial.

"The defendants were lying year after year," Wallace said in his opening statement.

A constant presence in court during the trial, Wallace joined the New York AG's office in 2018 after working in the private sector for 15 years.

Wallace and Trump sparred for hours during Trump's April deposition, according to a transcript of the deposition that was subsequently released by the AG's office.

"We're going to be here until midnight if your client answers every question with an eight-minute speech," Wallace remarked after one of Trump's lengthier answers.

Wallace tried to press Trump on spreadsheets that Wallace displayed during the deposition, promoting frequent objections from Trump's lawyers.

"Oh my God -- are you people capable of reading a spreadsheet?" an exasperated Wallace said after one objection from Trump's attorney Chris Kise.

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.

Doug Larson's name appears across five years of Donald Trump's financial documents, according to records entered into evidence.

A longtime professional appraiser with the real estate firm Cushman & Wakefield, Larson was cited in Trump Organization documents as an expert at valuing properties like 40 Wall Street, Trump Tower, and an adjoining retail space called "Niketown." Spreadsheets entered as evidence explicitly reference multiple phone calls with Larson between 2013 and 2017.

When asked about these phone calls in court, Larson testified that no such conversations occurred.

"Is it fair to say that Mr. Trump valued Trump Tower at $526 million in conjunction with you?" state attorney Mark Ladov asked Larson.

"No, that is incorrect," Larson said.

"Were you aware that Mr. McConney was citing you as a valuation source in his work papers?" Ladov asked.

"No, I was not," replied Larson, who said he did not assist Trump Organization executives in valuing Trump Tower, Niketown, or 40 Wall Street, despite Trump's paperwork referencing him as a source.

Evidence presented by the state instead suggested that the valuations were determined using cherry-picked metrics from a generic email Larson sent clients.

"It's a way to get your name out to clients for potential work," Larson said about one such "email blast" that was used in a Trump Tower valuation.

Larson added that the valuations Trump Organization executives determined based on "consultation" with him used flawed methodologies, such as using capitalization rates related to office buildings to appraise the retail Niketown building.

"It doesn't make sense," Larson said about Niketown's $287 million valuation.

"It's inappropriate and inaccurate," Larson said about the Trump Organization relying on his name to support their valuations. "I should have been told, and appraisals should have been ordered."