WASHINGTON — Hunter Biden appeared Wednesday on Capitol Hill for a closed-door deposition with lawmakers, a critical moment for Republicans as their impeachment inquiry into his father and their family's business affairs teeters on the brink of collapse.

The deposition marks a decisive point for the 14-month Republican investigation into the Biden family, which has centered on Hunter Biden and his overseas work for clients in Ukraine, China, Romania and other countries. Republicans have long questioned whether those business dealings involved corruption and influence peddling by President Joe Biden, particularly when he was vice president.

Yet after conducting dozens of interviews and obtaining more than 100,000 pages of documents, Republicans have yet to produce direct evidence of misconduct by the president. Meanwhile, an FBI informant who alleged a bribery scheme involving the Bidens — a claim Republicans had cited repeatedly to justify their probe — is facing charges from federal prosecutors who accuse him of fabricating the story.

Despite the stakes of their investigation, it remains unclear how much useful information Republicans will be able to extract from Hunter Biden during the deposition. He is under federal investigation and has been indicted on nine federal tax charges and a firearm charge in Delaware, which means he could refuse to answer some questions by asserting his Fifth Amendment rights.

The task of interviewing Hunter falls primarily to Reps. James Comer and Jim Jordan, the GOP chairmen leading the impeachment investigation. They first subpoenaed Hunter Biden in November, demanding that he appear before lawmakers in a private setting. Biden and his attorneys refused, warning that his testimony could be selectively leaked and manipulated. They insisted that Hunter Biden would only testify in public.

On the day of the subpoena, Hunter Biden not only snubbed lawmakers waiting for him in a hearing room — he did also while appearing right outside the Capitol, holding a press conference where he denounced the investigation into his family.

Both sides ultimately agreed in January to a private deposition with a set of conditions. The interview with Hunter Biden will not be filmed and Republicans have agreed to quickly release the transcript.

“Our committees have the opportunity to depose Hunter Biden, a key witness in our impeachment inquiry of President Joe Biden, about this record of evidence,” Comer, chair of the House Oversight Committee, said in a statement to The Associated Press. “This deposition is not the conclusion of the impeachment inquiry. There are more subpoenas and witness interviews to come.”

Hunter will be the second member of the Biden family questioned by Republicans in recent days. They conducted a more than eight-hour interview last week with James Biden, the president's brother. He insisted to lawmakers that Joe Biden has “never had any involvement," financially or otherwise, in his business ventures.

Looming large over the interview are developments on the other side of the country in Nevada, where federal prosecutors this month indicted an FBI informant, Alexander Smirnov, who claimed there was a multimillion-dollar bribery scheme involving the president, his son Hunter and a Ukrainian energy company. Prosecutors in court documents assert that Smirnov has had “extensive and extremely recent" contact with people who are aligned with Russian intelligence.

Smirnov's attorneys have said he is presumed innocent.

Republicans pressed the FBI last summer over the informant's claims, demanding to see the underlying documents and ultimately releasing the unverified information to the public. The claim was cited repeatedly in letters that House Republicans sent to impeachment witnesses.

Many GOP lawmakers say they have yet to see evidence of the “high crimes and misdemeanors” required for impeachment, despite alleged efforts by members of the Biden family to leverage the last name into corporate paydays domestically and abroad.

But the Republican chairmen leading the impeachment effort remain undeterred by the series of setbacks to their marquee investigation. Jordan, the chair of the House Judiciary Committee, said last week that the informant's indictment “does not change the fundamental facts” that the Biden family tried to benefit off the family name in several overseas businesses.

And Comer told Fox News on Tuesday that Smirnov was never “a key part of this investigation."

Both Comer and Jordan have insisted for the past year that their investigation and inquiry is focused solely on Joe Biden and what actions, if any, he took while as vice president or president to benefit his family. But at nearly every turn, their probe has had a consistent and heavy focus on Hunter Biden. Several lines of inquiry have been opened into Hunter's international business affairs, his artwork sales and even his personal life and on-and-off battle with addiction.

Meanwhile, Hunter Biden has no shortage of legal headaches off Capitol Hill as he faces criminal charges in two states from a special counsel investigation. He’s charged with firearm counts in Delaware, alleging he broke laws against drug users having guns in 2018, a period when he has acknowledged struggling with addiction. Special counsel David Weiss filed additional charges late last year, alleging he failed to pay about $1.4 million in taxes over three years.

He has pleaded not guilty in both cases.