(WASHINGTON) -- News that President Joe Biden's son, Hunter Biden, has agreed to a plea deal regarding a pair of tax-related misdemeanors follows a five-year Justice Department probe into the younger Biden's finances and comes as a GOP-led congressional panel investigates what House Oversight Committee Chairman James Comer says are the Biden family's "shady business deals."
After years of largely avoiding public confrontations about his business dealings, Hunter Biden earlier this year engaged a new legal team to undertake a more aggressive legal tack, making private citizen criminal referrals and sending cease-and-desist letters involving some of his most vocal critics.
Here's a look at the various investigations into the president's son:
Justice Department probe
Federal authorities with the U.S. attorney's office in Delaware, led by U.S. Attorney David Weiss, a Trump-era appointee, had been investigating Hunter Biden since 2018, but the probe was temporarily paused for several months ahead of the 2020 presidential election.
The investigation spilled into public view in December of 2020, shortly after Joe Biden secured the presidency, when Hunter Biden confirmed the probe into his "tax affairs." Prosecutors have examined whether he paid adequate taxes on millions of dollars of his income, including money he made from multiple overseas business ventures.
Prosecutors also explored allegations that Hunter Biden lied about his drug use on a gun application form in 2018, despite later acknowledging that he was addicted to drugs around that time.
ABC News has previously reported that the younger Biden borrowed $2 million from his lawyer and confidant Kevin Morris to pay the IRS for back taxes, penalties and liens that he owed.
A grand jury empaneled in Delaware reportedly heard testimony from multiple witnesses over the course of their probe, including some of Hunter Biden's business partners and a woman who had a child by Hunter Biden out of wedlock.
The younger Biden, a Yale-trained lawyer, has said he is cooperating with investigators and remained "100% certain" that he would be cleared of any wrongdoing. President Biden has said he and his son never discussed his foreign business dealings and there are no indications that the federal investigation involves the president in any way.
The White House has repeatedly sought to distance the president from the probe.
Meanwhile, on Capitol Hill, House Republicans have been conducting a long-expected investigation into Hunter Biden and his father.
Last month the powerful House Oversight Committee issued a subpoena to the FBI demanding the bureau produce a record related to an "an alleged criminal scheme involving then-Vice President Biden and a foreign national relating to the exchange of money for policy decisions."
The subpoena seeks an unclassified FD-1023 document, which is generally defined as a report from an informant. An FD-1023 form could be generated in a variety of situations involving someone presenting themselves as a "source" with claims of wrongdoing.
The White House denounced the accusation as "anonymous innuendo."
In April, a supervisor at the IRS told lawmakers that he had information that suggested the Biden administration was possibly mishandling the investigation into Hunter Biden, sources familiar with the matter told ABC News.
In a letter to lawmakers obtained by ABC News, the lawyer for the IRS whistleblower said his client was an IRS criminal supervisory special agent "who has been overseeing the ongoing and sensitive investigation" and "would like to make protected whistleblower disclosures to Congress."
The disclosures, the letter said, "(1) contradict sworn testimony to Congress by a senior political appointee, (2) involve failure to mitigate clear conflicts of interest in the ultimate disposition of the case, and (3) detail examples of preferential treatment and politics improperly infecting decisions and protocols that would normally be followed by career law enforcement professionals in similar circumstances if the subject were not politically connected."
Attorney General Merrick Garland, who had testified on Capitol Hill that the Hunter Biden probe was free from any improper political interference, responded to the letter by saying he stood by that statement.
"I stand by my testimony, and I refer you to the U.S. attorney for the District of Delaware who is in charge of this case and capable of making any decisions that he feels are appropriate," Garland said last month.
House Oversight Committee Chairman Comer and Rep. Jim Jordan, chairman of the House Judiciary Committee, pledged after November's election to "pursue all avenues" of wrongdoing and called investigations into the president's family a "top priority."
In February, former Twitter executives testified before the Oversight Committee that the social media company made a mistake in blocking users from sharing a controversial 2020 New York Post story about Hunter Biden's laptop.
President Joe Biden subsequently dismissed the Oversight Committee's probe in an interview with PBS NewsHour.
"[The] public's not going to pay attention to that," he said. "If the only thing they can do is make up things about my family, it's not going to go very far."
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