The People of the State of New York v. Donald J. Trump, et al, is scheduled to get underway in lower Manhattan at 10 a.m. with opening statements.

If opening statements are completed before the end of the day, the New York attorney general plans to begin her case by calling Trump's former Mazars USA accountant Donald Bender to the stand.

Mazars severed its business relationship with the former president last year after learning of the attorney general's findings during the AG's probe.

Though Trump has denied all wrongdoing alleged by the attorney general, Judge Arthur Engoron has already decided the central allegation against Trump and his co-defendants, ruling in a pretrial hearing last week that the AG had provided "conclusive evidence" that Trump overvalued his assets between $812 million and $2.2 billion.

The judge then canceled the Trump Organization's business certificates in New York, severely restricting Trump's ability to conduct business in the state moving forward -- a move that Trump attorney Alina Habba called "nonsensical" and "outrageously overreaching."

"In defendants' world: rent regulated apartments are worth the same as unregulated apartments; restricted land is worth the same as unrestricted land; restrictions can evaporate into thin air," Engoron wrote, citing multiple arguments made by defense to justify the allegedly inflated valuations of Trump's assets. "That is a fantasy world, not the real world."

Among the issues still to be determined at trial: What additional penalties Trump might face, and what might happen with the multiple causes of action included in the attorney general's suit.

Former President Donald Trump stepped up his attacks on the judge overseeing and deciding his case, writing on Truth Social overnight that Justice Arthur Engoron should resign and be sanctioned for "abuse of power."

Similar to an earlier post, Trump criticized allegations regarding the value of his Mar-a-Lago estate, in addition to an appellate court's ruling that his lawyers unsuccessfully tried to use to limit the timeframe of the case.

Former President Trump posted on his Truth Social platform Sunday night that he intends to attend the opening of the trial.

"See you in court -- Monday morning," he wrote in a post.

Earlier Sunday, multiple sources familiar with the decision told ABC News that Trump was expecting to attend.

Trump will have no speaking role in court on Monday, but it is anticipated that he'll return to the courthouse toward the end of the state's case when court records show he will be called as a witness.

Patrick Birney had been working for the Trump Organization for more than two years when a magazine article prompted him to change Trump's financial statement, the executive testified.

"There was an article written that stated that Mr. Trump's triplex was actually 10,900 or so square feet," Birney said, referring to a 2017 Forbes magazine article that alleged Trump had been lying about the size of his residence. (Judge Engoron decided in his partial summary judgment last month that the size was misrepresented.)

Birney, who was an assistant VP at the time, testified that Trump Organization executives, including former CFO Allen Weisselberg, "verified" the size and adjusted the next year's statement of financial condition. As a result, the penthouse was valued at $116 million in 2017 -- a steep drop from the 2016 valuation of $327 million.

Birney testified that he looked up comparable properties to come up with the value of the apartment going forward.

"I Google searched recent penthouse sales in Manhattan," Birney said, eventually landing on an web article about a penthouse purchased by billionaire Ken Griffin that set the record for most expensive home ever sold in the United States.

A price-per-square-foot for Trump's penthouse was determined based on that record-breaking sale, Birney said.

When Birney was tasked with finding comparable properties to value Trump's Mar-a-Lago Club, he similarly searched for nearby Palm Beach homes. However, Trump signed a deed in 2002 that limited Mar-a-Lago's purpose to a social club, the New York attorney general alleges, making the price of nearby residences irrelevant.

Asked if he was ever told about the deed by anyone at the Trump Organization, Birney replied, "I don't believe I was." Instead, he said he first learned about it during an "interview with the attorney general's office."

Court then adjourned for the day, with Birney's testimony scheduled to resume tomorrow morning.