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.

As court resumed after the lunch break, Judge Engoron admonished Donald Trump for a post he made this afternoon on his Truth Social platform regarding Engoron's clerk, Alison Greenfield.

"Personal attacks on members of my court staff are unacceptable and inappropriate. Consider this statement a gag order forbidding all parties from posting, emailing or speaking publicly about any of my staff," the judge said in his admonishment.

The post, which included a photo of Greenfield with Senate Majority Leader Chuck Schumer, made unsubstantiated claims about her connections with Schumer and falsely claimed that Greenfield is "running" the case against Trump.

Trump apparently made the post, which linked to Greenfield's Instagram account, while the former president was sitting in the courtroom.

The post was deleted shortly before the judge's admonishment, but it was up for at least an hour and a half. Engoron lamented that the sentiment was shared to millions.

The judge did not mention Trump by name but noted the post came from one of the defendants.

Greenfield sits at the bench to Engoron's immediate right and the judge is often seen conferring with her over legal and logistical matters.

In a statement, Schumer spokesperson Allison Biasotti called Trump's post "ridiculous, absurd, and false," saying that "Sen. Schumer does not know Ms. Greenfield. As is well known, Sen. Schumer attends countless events in every corner of the state where tens of thousands of constituents take photos with him, just like this one, which was taken at a stop at an annual brunch in Manhattan.”

-ABC News' Peter Charalambous, Aaron Katersky, Soo Rin Kim, Lalee Ibssa and Kendall Ross