Before today's first witness entered court, Trump attorney Chris Kise asked Judge Engoron to postpone today's proceedings after five members of the New York attorney general's team tested positive for COVID-19.

Describing the attorney general's conduct as "beyond irresponsible," Kise said that his team did not get adequate notice about the COVID exposures despite having close contact with positive individuals.

"Nothing else matters except for pursuing President Trump," Kise said. "We have the leading candidate for president of the United States in the courtroom today."

"The attorney general's office knew on Wednesday and didn't tell any of us," defense attorney Clifford Robert said. "We are truly in an outbreak."

Engoron declined to grant their requested delay.

In a statement, a spokesperson for New York Attorney General Letitia James said the state has complied with all CDC guidelines.

"Our office properly notified the court and defendants' counsel, and the court decided to proceed with trial today. If there were any concerns, defendants could wear masks today or at any point, but they have opted not to," the spokesperson said.

Trump called his former lawyer Michael Cohen a "proven liar" and "felon" as Trump entered the courtroom for his civil trial this morning.

"He's a felon, served a lot of time for lying, and we're just going to go in and see and I think you'll see that for yourself," Trump told reporters outside court.

Cohen pleaded guilty in 2018 to two separate criminal cases and eventually spent more than 13 months in prison -- but said that it was Trump who caused him to "follow a path of darkness."

-ABC News' Ricardo Montero contributed to this report.

Exiting his New York City apartment this morning, Michael Cohen told reporters he was "looking forward" to seeing Trump in court.

"It's been five years since we've been in the same room," Cohen said.

Cohen preemptively defended the credibility of his testimony and reiterated that he previously perjured himself "concert with and for the benefit of Donald J. Trump."

"My credibility should not be in question," Cohen said.

-ABC News' Eric Avram contributed to this report.

Donald Trump has arrived in court for the anticipated testimony of his former lawyer Michael Cohen.

New York Attorney General Letitia James is also attending the trial this morning.

James took her usual seat at the front of the courtroom's gallery, directly behind her team of lawyers at the counsel table.

The courtroom itself is nearly at capacity, with attendance matching the number of observers during the trial's opening statements.

When the Trump Organization valued its Seven Springs compound in New York's Westchester County at $261 million, the company included seven mansions, estimated to be worth $23 million each, that had not been built, longtime Trump Organization controller Jeff McConney testified.

In contrast, an appraiser had said Seven Springs was worth $56 million, excluding development rights for the property, which hadn't been awarded.

McConney testified that he did not factor into the valuation when, or whether, the homes would be built.

"You have treated, for the purposes of this valuation, a profit of $23 million per home as if it were realized immediately?" asked Andrew Amer with the New York attorney general's office.

"Correct," McConney said.

Amer said that Trump Organization VP Eric Trump, in a call with McConney the following year, instructed McConney to continue to value the seven mansions the same as he did in 2013.

McConney is testifying as a hostile witness since he is also a named defendant in the case. It gives Amer wider latitude in his examination, though defense attorneys have made several objections about leading questions.

The proceedings were briefly interrupted by the blaring of a horn that was audible in the courtroom, prompting Amer to interrupt his questioning and remark, "Someone is having a celebration."

Judge Engoron, who has displayed a dry wit throughout the trial, responded, "Maybe they're celebrating us."