Donald Trump's defense team plans to call their first of several expert witnesses to the stand today.

Steven Witkoff, a New York-based real estate investor and developer, is set to testify about his expert opinion that the Trump National Doral golf course in Miami was undervalued in Trump's financial statement, despite the attorney general's claim to the contrary.

The expert report Witkoff prepared for the case also criticized the finding from the state's expert regarding the value of Trump's 40 Wall Street property.

During a 2018 roundtable on tax reform, Trump called Witkoff a "pal" who he inspired to enter the real estate industry.

"You know, people don't realize Steve started out as a lawyer -- a very good lawyer, a top lawyer in New York. And then he said, 'I'm going to go into the real estate business because I can do this, too," Trump said. "He saw me do it, and he said, 'If Trump can do it, I guess I can do it, right?'"

In a video statement posted to social media, New York Attorney General Letitia James said that the testimony of Donald Trump Jr. yesterday failed to refute any of her case against Donald Trump and his adult sons.

"After spending a full day walking through a marketing presentation to sell us all on the greatness of the Trump Organization, the defendants did not make a single point to refute the case we brought against them," James said of Trump Jr., who led off the defense's case.

Trump's eldest son, an executive VP with the family firm, functionally served as a summary witness to explain the history and notable assets of the Trump Organization, repeatedly using words like "spectacular" and "incredible" to spell out the details of Trump's properties.

James, meanwhile, drew the ire of Donald Trump for appearing to smile in court.

"A.G. Letitia James is smirking all day long from her seat in Court, as New York continues to set records in murder and other violent crimes, and businesses flee to other States," Trump wrote on Truth Social this morning, despite murders in New York City being down nearly 10% this year according to the NYPD.

The defense wrapped up the first day of its case with testimony from Donald Trump's former external tax lawyer, Sheri Dillon, who returned to the witness stand to clarify her actions related to conservation easements at Trump's properties.

Dillon previously testified during a lengthy and combative portion of the state's case.

"Welcome back. I feel like I am at a reunion -- Trump trial reunion," Judge Engoron joked when Dillon returned to the courtroom.

Dillon, explaining a potential gap in email communications about specific deals, testified that she often communicated with Eric Trump over the phone.

"If I picked up the phone and talked to him, I would know he knew what he needed to know," Dillon testified.

She also said she advised Trump's appraiser, David McArdle, that the company could add 40 additional residential units at Trump National Golf Club in New York's Westchester County by filing a new offering plan, according to an email shown in court. The clarification challenges the New York attorney general's allegation that a $101 million increase in the value of undeveloped land was based on an unfounded plan by Eric Trump to add units to the property.

During a short cross-examination, state attorney Louis Solomon attempted to challenge Dillon's authority to provide such legal information to McArdle.

"Do you know if a sponsor has a right to have an offering plan accepted for filing merely because the development meets the requirements for zoning?" Solomon asked.

"No, I do not," she responded.

Dillon concluded her testimony, and court then adjourned for the day.

Speaking outside the courthouse following his testimony for the defense, Donald Trump Jr. told ABC News that he seems to have a positive relationship with Judge Engoron.

"Perhaps there's a New York personality there, but no I think he understood," Trump Jr. said when ABC News suggested he and the judge appeared to get along. "I can't help myself even in this very serious situation. If you take yourself too seriously the world sort of sucks. You got to have a little bit of fun with it, so I did."

His relationship with the judge appears to stand in contrast to that of his father, who has accused Engoron of bias and insulted him from the witness stand.

"We had some quips in the courtroom the first time I was here," Trump Jr. said of Engoron. "Sort of gave me a fist bump on the way out. I guess I had a rather snappy response to something that was -- I can't even remember what it was right now. He said, 'That was really funny.'"

Asked by ABC News whether Trump Jr. shared his father's views about the judge being biased, the son demurred.

"Listen, I don't even know how far the gag order applies, so I don't need to do that and put myself -- I'm in enough crosshairs, guys," he said.

Former President Donald Trump's plan to deliver part of his closing argument Thursday, as reported yesterday by ABC News, is now in doubt after he failed to meet a deadline to agree to limitations imposed by Judge Arthur Engoron.

According an email exchange between Engonon and defense counsel that was posted to the public docket Wednesday, Engoron said that Trump would have to follow the case's limited gag order, and that he would not be allowed to "impugn" the New York attorney general or her staff -- limitations that Trump attorney Chris Kise rejected, calling them "untenable."

"The limitations I am imposing, in my absolute discretion, are not subject to further debate. Take it or leave it," Engoron replied on Jan. 9, according to the email thread.

When Trump's lawyers missed the first deadline set by Engoron, the judge determined that Trump could not testify. Kise then responded that he did not see the deadline and requested that the closing arguments be postponed because of the death of Melania Trump's mother on Tuesday.

"I am sad to advise the Court that Mrs. Trump's mother passed away this evening. Because of the challenges presented by this deeply personal family matter, President Trump has asked that I request the Court postpone the date for closing argument," Kise wrote yesterday.

Engoron promptly denied the request and said the closings would continue as planned.

"On balance, going forward makes the most sense. Please tell Mr. Trump that I am sorry," Engoron wrote.

Kise informed Engoron that Trump still planned to attend the closings and speak.

"Despite the fact that his Mother-in Law, who he was very close to, passed away late last night, President Trump will be speaking tomorrow," Kise said in an email this morning.

When Engoron asked for assurance that Trump agreed to his rules, Kise pushed back, writing, "You are not allowing President Trump, who has been wrongfully demeaned and belittled by an out of control, politically motivated Attorney General, to speak about the things that must be spoken about."

"I won't debate this yet again. Take it or leave it. Now or never. You have until noon, seven minutes from now. I WILL NOT GRANT ANY FURTHER EXTENSIONS," Engoron replied at 11:54 a.m.

After Kise failed to respond, Engoron emailed him at 12:12 p.m. that he assumed Trump would not be speaking and that their email exchange would be posted to the court's public docket.

Responding to the development, Trump's legal spokesperson, Alina Habba, said in a statement to ABC News: "Is anyone surprised anymore?"