Former GOP Rep. Denver Riggleman, who previously served as a senior technical adviser for the House select committee that investigated the January 6, 2021, attack at the US Capitol, is working with the legal team advising President Joe Biden's son.

Riggleman's work is similarly focused on assessing data issues. He is assisting Hunter Biden's attorneys as they grapple with increasing scrutiny from House Republicans over business dealings involving the president's son.

"I and my forensics, data, and telephony team are conducting data investigations and analysis for Hunter Biden's legal team," Riggleman told CNN in a statement, noting his concentration is on "data across the spectrum."

CBS News first reported Riggleman's work with Hunter Biden's legal team.

Hunter Biden's lawyers recently lashed out against IRS whistleblowers who testified to Congress that the president's son received preferential treatment from the Justice Department.

The lawyers were publicly pushing back against claims from two IRS agents that the Justice Department officials slow-walked a criminal probe into Hunter Biden's tax issues, stymied their efforts to obtain subpoenas and search warrants, and repeatedly blocked prosecutors from filing felony charges.

The whistleblowers' claims of political interference in the criminal probe have been met with adamant denials from the Justice Department. Attorney General Merrick Garland and David Weiss, the Trump-appointed US attorney who oversaw the five-year investigation, have said that Weiss had full authority to run the investigation, and to bring charges whenever and wherever he wanted.

The investigation culminated in a plea deal for Hunter Biden, who will admit to two tax misdemeanors and avoid prosecution on a felony gun charge if he follows court-imposed rules for a set period of time.

Hunter Biden is slated to plead guilty in federal court in Wilmington, Delaware, on July 26.