The House committees leading the impeachment inquiry against President Biden are expected to grill top witnesses behind closed doors this month as the investigation reaches a critical phase.

Assistant U.S. Attorney Lesley Wolf is up first this month. She is expected to answer questions during a deposition that begins at 10 a.m. Tuesday before the House Judiciary Committee.

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House Judiciary Committee Chairman Jim Jordan, R-Ohio, subpoenaed Wolf last month amid whistleblower allegations that she sought to block investigators from asking questions related to President Biden throughout the years-long federal investigation into Hunter Biden.

Jim Jordan speaks before House subcommittee

Rep. Jim Jordan, R-Ohio (Caroline Brehman/CQ-Roll Call Inc. via Getty Images)

Jordan, over the summer, initially asked Wolf to appear for a voluntary transcribed interview as part of the committee’s oversight investigation into the DOJ’s handling of the Hunter Biden probe, but she denied that request.

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IRS whistleblower Gary Shapley alleged that Wolf worked to "limit" questioning related to President Biden and apparent references to Biden as "dad" or "the big guy."

Wolf allegedly said there was "no specific criminality to that line of questioning" relating to President Biden, which Shapley said "upset the FBI."

In October 2020, Wolf reviewed an affidavit for a search warrant of Hunter Biden’s residence and "agreed that probable cause had been achieved," Shapley testified. However, Shapley said Wolf ultimately would not allow a physical search warrant on the president’s son.

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Shapley said Wolf determined there was "enough probable cause for the physical search warrant there, but the question was whether the juice was worth the squeeze."

A split image shows IRS whistleblower Gary Shapley and President Biden with his son Hunter Biden

A circle insert featuring IRS whistleblower Gary Shapley with Hunter Biden and President Biden in the background (Fox News/AP Photo/Andrew Harnik)

Wolf allegedly said "optics were a driving factor in the decision on whether to execute a search warrant," Shapley said, adding that Wolf agreed that "a lot of evidence in our investigation would be found in the guest house of former Vice President Biden but said there is no way we will get that approved."

Wolf also allegedly tipped off Hunter Biden’s legal team ahead of a planned search of his storage unit.

Jordan, who is co-leading the House impeachment inquiry against President Biden, is focusing on depositions and transcribed interviews of witnesses related to whether politics improperly influenced prosecutorial decisions throughout the Hunter Biden investigation.

The Judiciary Committee has heard from top prosecutors involved in the probe, including now-Special Counsel David Weiss, who has been leading the investigation into Hunter Biden since its inception in 2018.

Weiss, during his interview before the committee last month, admitted he "wasn’t granted" special attorney authority in his Hunter Biden investigation by the Justice Department despite requesting that status, but he told investigators he did not interpret that decision as a "denial in any way, shape or form," according to a transcript of his testimony reviewed by Fox News Digital.

Special Counsel David Weiss

U.S. Attorney for the District of Delaware David Weiss (Fox News screenshot)

That response confirmed Shapley’s recollection that Weiss requested special counsel authority but was denied, that he did not have "ultimate authority" in the probe to pursue charges against the president's son.

Weiss said he followed steps requested by the DOJ, asking U.S. attorneys in separate districts if they would like to partner with him in the prosecution.

Both U.S. Attorney for D.C. Matthew Graves and U.S. Attorney for the Central District of California Martin Estrada testified during their voluntary transcribed interviews before the House Judiciary Committee that they declined to partner with Weiss – also confirming Shapley’s allegations.

The House Judiciary Committee is expecting additional witnesses for transcribed interviews before the end of the year.

Jason Smith

House Ways and Means Chairman Jason Smith (Bill Clark/CQ-Roll Call Inc. via Getty Images)

Meanwhile, House Ways and Means Committee Chairman Jason Smith, R-Mo., will hold a public executive session on Tuesday that is to feature testimony from IRS whistleblowers Gary Shapley and Joseph Ziegler. They are expected to defend their claims related to the Hunter Biden investigation in a public setting.

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Fox News Digital has also learned that Smith will be releasing additional information related to his investigation on Tuesday. 

Supervisory IRS Special Agent Gary Shapley, left, and IRS criminal investigator Joseph Ziegler are sworn in before giving testimony at a House Oversight Committee hearing related to the DOJ's investigation of Hunter Biden.

Supervisory IRS Special Agent Gary Shapley, left, and IRS criminal investigator Joseph Ziegler are sworn in before giving testimony at a House Oversight Committee hearing related to the DOJ's investigation of Hunter Biden. (Drew Angerer/Getty Images)

And the House Oversight Committee is expecting Hunter Biden for his closed-door deposition next week on Dec. 13. Oversight Chairman James Comer, R-Ky., subpoenaed Hunter Biden last month.

The president’s son’s attorney, Abbe Lowell, said Hunter Biden would appear for the deposition but instead requested a public hearing to answer questions before the American people.

Comer said a deposition has to come first in order for the committee to continue its fact-finding efforts, but he told Fox News Digital he would release Hunter Biden's deposition transcript and will schedule a public hearing for the president’s son.

James Comer, Hunter Biden split

Rep. James Comer, R-Ky., left, said he believes the ongoing investigations into Hunter Biden, right, by House Republicans have been given more credibility after a plea deal for the president's son fell apart. (Mandel Ngan/AFP | Ting Shen/Bloomberg via Getty Images)

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Comer also subpoenaed the president’s brother, James Biden. It is unclear when his deposition will take place.

Comer has requested sit-down transcribed interviews with a number of Biden family members and Hunter Biden business associates, like Rob Walker.

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Separately from the Hunter Biden-related investigative steps, Comer has also subpoenaed former White House counsel Dana Remus to appear for a deposition and answer questions related to President Biden’s alleged improper retention of classified materials. Comer requested several other officials for interviews on the matter in an effort to determine whether the classified materials he held contained information related to the foreign countries with which his family was engaged in business.