WASHINGTON (AP) — President Joe Biden’s son, Hunter Biden, faced new challenges on the eve of a scheduled court appearance Wednesday in which he’s set to plead guilty in a deal with prosecutors on tax and gun charges.

On Capitol Hill, where Republicans are ramping up their investigations of the president and his son, the GOP chairman of the House Ways and Means Committee took the unusual step of filing court documents urging the judge in Hunter Biden’s case to consider testimony from IRS whistleblowers. The whistleblowers alleged the Justice Department interfered with investigations into Biden, a charge that has been denied by the lead prosecutor in the case, who was appointed by former President Donald Trump.

U.S. District Judge Maryellen Noreika, who was also appointed by Trump, will consider whether to accept the plea agreement. Judges rarely throw out plea bargains, but the effort to intervene by Ways and Means Chairman Jason Smith of Missouri amounted to a high-profile push to raise questions about the deal, which is expected to spare the president’s son from jail time.

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The dynamics of the case became even more complicated hours after the lawmakers filed their motion. A court clerk received a call requesting that “sensitive grand jury, taxpayer and social security information” it contained be kept under seal, according to an oral order from Noreika.

The lawyer gave her name and said she worked with an attorney from the Ways and Means Committee but was in fact a lawyer with the defense team, a clerk wrote in an email to Theodore Kittila, an attorney representing Smith.

When Noreika learned of the situation, she demanded the defense show why she should not consider sanctioning them for “misrepresentations to the court.”

Defense attorneys answered that their lawyer had represented herself truthfully from the start, and called from a phone number that typically displays the firm’s name, Latham & Watkins, on the caller ID. Jessica Bengels said in court documents that she did speak to two different clerk’s office employees, which could have contributed to the misunderstanding. The second employee emailed Kittila.

Biden’s attorneys are still seeking to keep information deemed private out of the public court record. Kittila, though, said he had only filed materials that the committee had already released publicly online. The judge agreed to keep the information sealed for a day to consider the issue.

The dustup came hours before Biden is expected to plead guilty to misdemeanor tax charges in an agreement that allows him to avoid prosecution on a gun charge if he means certain conditions. Republicans have decried the agreement as a “sweetheart deal” and heard from two IRS agents who claimed the long-running investigation was “slow walked” and the prosecutor overseeing it was refused broader special counsel powers.

Delaware U.S. Attorney David Weiss, a Trump appointee, denied that in a letter to Congress, saying he had “full authority” over the probe and never requested special counsel status.

A spokeswoman for Weiss directed queries back to the court clerk’s office.