Republican lawmakers have made allegations of wrongdoing by President Joe Biden’s son a central line of attack.

On Friday, Attorney General Merrick Garland elevated David Weiss, a federal prosecutor who has been handling the younger Biden’s case, to special counsel, expanding his investigative authority.

“The appointment of Mr Weiss reinforces for the American people the department’s commitment to both independence and accountability in particularly sensitive matters,” Garland told reporters.

Special counsels are often appointed when the US Justice Department might otherwise have a conflict of interest in pursuing a case.

Endowed with special investigative powers — as well as the ability to prosecute — special counsels act independently of the department’s day-to-day management, though they are subject to the same rules.

The Justice Department falls under the executive branch, and Weiss’s appointment to special counsel could indicate the Biden administration is attempting distance itself from a much-expected trial of the president’s son.

Republican lawmakers have made Hunter Biden a central focus of their investigative efforts in Washington, as well as a frequent target for criticism.

The younger Biden has been accused of leveraging his family’s political status to win lucrative contracts in countries such as China and Ukraine. Hunter Biden also faces misdemeanors for tax evasion and a felony charge for illegally possessing a gun during his longtime struggle with cocaine and alcohol addiction.

Some Republicans have also sought to tie Hunter Biden’s business dealings to his father’s presidency, but so far no evidence has emerged linking the two, and the White House has dismissed such claims as “insane conspiracy theories”.

Weiss first filed the criminal charges for tax evasion and gun possession in June. But a federal judge rejected a proposed plea deal, which would have allowed Hunter Biden to avoid trial and possibly receive a lighter sentence in exchange for a guilty plea.

Weiss said in a court filing on Friday that the talks over a plea deal had reached an “impasse” and a trial was likely. On July 26, after the plea deal was rejected, Hunter Biden pleaded not guilty to the tax charges.

Al Jazeera’s Heidi Zhou-Castro, reporting from Washington, DC, said the case “adds another complication” to Biden’s 2024 re-election campaign.

“Republicans have long used Hunter Biden as sort of an Achilles heel in attacking his father,” Zhou-Castro said.

She said Weiss’s appointment as special counsel “would seem to offer credibility to Republicans’ concerns that there’s still more to dig up” against Hunter Biden.

But Republicans see the special counsel appointment “both as an elevation of their claims against Biden and also something to complain about”, Zhou-Castro explained.

Weiss’s elevation to special counsel could make it more difficult for Republican lawmakers to get him to testify before Congress should they ever launch an impeachment hearing against President Biden.

Conservative political figures have long pointed to Hunter Biden’s scandals as evidence of a double standard in the treatment of President Biden and former President Donald Trump.

Trump, the Republican frontrunner in the 2024 presidential race, was dogged by allegations of wrongdoing during his time in office and was impeached twice: once for abuse of power and obstruction and the second for inciting the attack on the US Capitol on January 6, 2021.

He currently faces three criminal indictments, including for election interference.

Federal ethics law prohibits the use of public office for private gain. Both the Trump and Biden families have faced accusations of doing so from across the political aisle.