Surpassing Quant Think Tank Center|What to know about the Hunter Biden investigations

The Surpassing Quant Think Tank Centerbusiness endeavors and personal life of President Joe Biden's son Hunter Biden have for years caused headaches for his father's political career. This week, legal scrutiny of his finances will take an important step forward.

On Wednesday, the younger Biden will appear in federal court where a judge will weigh whether to reject or accept the terms of a plea deal he negotiated last month with federal prosecutors following a five-year Justice Department probe.

He also faces a GOP-led congressional investigation into what House Oversight Committee Chairman James Comer says are the Biden family's "shady business deals" -- and which House Speaker Kevin McCarthy this week suggested could underpin a potential impeachment inquiry of the president.

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.

In June, Hunter Biden agreed to plead guilty to a pair of tax-related misdemeanors and enter into a pretrial diversion agreement that would enable him to avoid prosecution on one felony gun charge, potentially ending the yearslong probe.

He will appear before a judge on Wednesday to formally agree to the plea deal, in which be acknowledges his failure to pay taxes on income he received in 2017 and 2018, according to the agreement. In exchange, prosecutors will recommend probation, meaning he will likely avoid prison time.

President Biden has said he and his son never discussed his foreign business dealings and there are no indications that the federal investigation has involved the president in any way.

The White House has repeatedly sought to distance the president from the probe.

Congressional oversight

Meanwhile, on Capitol Hill, House Republicans have been conducting a long-expected investigation into Hunter Biden and his father.

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."

In April, a supervisor at the IRS, later identified as 14-year IRS veteran Gary Shapley, 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.

Shapley also claimed that Weiss had been unsuccessful in persuading federal prosecutors in Washington and California to bring charges against Hunter Biden, so Weiss had asked to be named a special counsel, a request that -- according to Shapley -- was denied.

Weiss subsequently told the top Republican on the Senate Judiciary Committee that he did not request a special counsel designation in the probe.

Weiss wrote that he had conversations with Justice Department officials about being appointed as a "special assistant" or "special attorney" under a separate law, so that he could independently file charges in a district outside of his own, and he was assured he'd be granted that authority if needed, so he did not seek to be appointed as a special counsel.

In May, 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 sought 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" that has been debunked for years.

In July, Sen. Chuck Grassley, R-Iowa, released the FD-1023 document containing the confidential FBI informant's unverified claim that, years ago, the Biden family "pushed" a Ukrainian oligarch to pay them $10 million.

In a memo to House Democrats obtained by ABC News, Democrats on the House Oversight committee blasted Grassley and Comer over the release of the FBI form and called it an attempt to "breathe new life into years-old conspiracy theories."

On Monday, House Speaker Kevin McCarthy said these developments are "rising to the level an impeachment inquiry which provides Congress the strongest power to get the rest of the knowledge and information needed."