Donald Trump and his co-defendants have filed a motion seeking a mistrial on the grounds that the trial has been "tainted" by the appearance of bias on the part of Judge Arthur Engoron and his law.

"This appearance of bias threatens both Defendants' rights and the integrity of the judiciary as an institution," Trump's attorneys say in the filing. "As developed herein, in this case the evidence of apparent and actual bias is tangible and overwhelming."

"Specifically, the Court’s own conduct, coupled with the Principal Law Clerk, Allison Greenfield’s unprecedented role in the trial and extensive, public partisan activities, would cause even a casual observer to question the Court’s partiality," they write.

"Such evidence, coupled with an unprecedented departure from standard judicial procedure, has tainted these proceedings and a mistrial is warranted," the filing says.

Donald Trump's lawyers are scheduled to resume their direct examination of expert witness Jason Flemmons this morning, continuing a line of questioning yesterday that largely placed responsibility for Trump's financial statements on Trump's external accountants.

Flemmons, who was qualified as an expert on accounting, explicitly criticized the testimony of Donald Bender, Trump's accountant at Mazars USA who was the New York attorney general's first witness, disputing Bender's claim that he would have wanted to see any appraisals that the Trump Organization conducted.

Flemmons also testified that Trump's financial statements should have sent a "buyer beware" signal to lenders due to the "highly cautionary language" in their disclaimer, which allowed Trump to make claims that significantly departed from generally accepted accounting principles.

To the extent that the statements and the Trump Organization's representations about the statements were inaccurate, Flemmons placed responsibility on Bender and his colleagues at Mazars, rather than the Trump Organization.

Expert witness Jason Flemmons cast doubt on the testimony of the Trump Organization's former external accountant Donald Bender, who said he would have wanted to review any appraisals that the Trump Organization conducted.

"That's not something that is required by professional standards," said Flemmons, testifying for the defense. "His testimony was not professionally plausible."

That prompted a strong objection from state attorney Kevin Wallace.

"Is he trying to say the witness is lying?" Wallace said.

"Not to put too fine a point on it," Judge Engoron quipped.

Asked to confirm what he meant by "professional plausible," Flemmons said it would be "highly unusual" for Bender to request appraisals outside what was mentioned in the statement of financial condition.

"Accountants in the industry do not go seeking records for things that are not in the four corners of the statement of financial condition," Flemmons said.

Court was subsequently adjourned for the day, with Flemmons scheduled to continue his testimony tomorrow.

Defense expert Jason Flemmons described the disclaimer included in Donald Trump's financial statement as the "highest level disclaimer" that could have been provided to bankers reviewing the document.

Flemmons said that the disclaimer, which he said includes "highly cautionary language," would allow a user to make claims that significantly departed from generally accepted accounting principles, known in the industry as GAAP.

"Was that language present in a substantially similar form in the compilation statements issued by Mazars for Donald Trump?" defense attorney Jesus Suarez asked.

"Yes," Flemmons said, adding that the disclaimer was "effectively saying 'user beware.'"

During his testimony and in statements to the media, Trump has claimed that the disclaimer shields him from liability in the case.

Suarez also used Flemmons' testimony to suggest that Trump's external accountants were responsible for understanding the methods used in the financial statement and determining their appropriateness.

That appeared to conflict with testimony of former Trump accountant Donald Bender of Mazars USA, who described his role as akin to plugging numbers provided by the Trump Organization into a template.

Earlier in his testimony, before breaking down on the witness stand, longtime Trump Organization controller Jeff McConney drew a blank when asked why Trump's Mar-a-Lago property was valued in Trump's statements of financial condition as a private residence rather than a social club -- a central allegation levied by the New York attorney general.

The property was valued in excess of $500 million on the basis that it could be sold as a private residence -- despite Trump signing a deed in 2002 with the National Trust for Historic Preservation that exclusively limited the property to being used as a club. The Palm Beach County Assessor subsequently appraised the market value of the club at less than $28 million, significantly lowering Trump's tax burden.

"I don't remember off the top of my head," how the property ended up being valued on Trump's financial statements as a residence, McConney said, confirming that was the case.

He testified that he could not remember having a specific conversation with outside accounting firm Mazars USA about the approach to valuing Mar-a-Lago.

While McConney could not recall why the decision to value the property as a private residence was made, he said that he used a reasonable approach to determining a price-per-acre based on nearby property sales. He said that their comparable property approach resulted in a $50 million decrease in value between 2014 and 2015.

"Our intention was always to reflect as best we could the value of these properties," McConney said.