A long-running investigation into the US President Joe Biden’s son, Hunter, may be heading for a jury trial.

The five-year probe appeared near its end last month, with Mr Biden, 53, agreeing to resolve tax and gun offences and avoid prison time.

But the case has since taken several dramatic twists and turns.

Mr Biden’s plea agreement unravelled in court, and federal prosecutors have since argued it is no longer binding.

The man who was overseeing the investigation, David Weiss, has now been elevated to special counsel, giving him greater prosecutorial authority.

The lawyer guiding Mr Biden’s case has withdrawn his representation amid concerns he may be called to testify against his client in the months ahead.

And all the while congressional Republicans have forged ahead with their own inquiries into Mr Biden’s foreign business dealings.

Here is a guide to the first son’s legal troubles.

In June, prosecutors with the US Department of Justice struck a two-part plea agreement with Mr Biden’s legal team.

Under the deal, he was to be charged with two misdemeanour counts for failing to pay his taxes on time in 2017 and 2018.

He was also to admit that he had illegally possessed a gun while being a drug user, and agree to drug treatment and monitoring in lieu of a more serious felony charge and possible jail time.

Republicans argued the president’s son was receiving “a sweetheart deal”.

That claim was bolstered by two tax investigators, who testified to Congress that they believed political considerations had hampered the probe and benefited Mr Biden.

At a hearing in Delaware last month, the deal crafted over several months dissolved under scrutiny from the federal judge overseeing the case.

Both sides negotiated unsuccessfully in full view of reporters, before District Judge Maryellen Noreika refused to “rubber stamp” what she called an “atypical” agreement.

David Weiss, the US attorney in Delaware, began investigating allegations of Mr Biden’s criminal conduct in 2019.

On 11 August, Attorney General Merrick Garland appointed Mr Weiss as special counsel, providing him with extra resources and the power to bring charges in other jurisdictions.

Republicans had previously advocated for the appointment of a special counsel, but have criticised the choice of Mr Weiss even though he is a Trump appointee.

They have pointed to Mr Weiss’ role in brokering the controversial plea deal, as well as the justice department’s delay in appointing a special counsel, to argue that he will “protect” Mr Biden from further prosecution and slow down their own inquiries.

The continuing legal battle will also now proceed without Christopher Clark, Mr Biden’s lead attorney for the past five years.

Mr Clark withdrew from the case on 15 August, writing in a court notice that he could be called as a witness in any potential trial to discuss the plea agreement.

Taking the baton from him is Abbe Lowell, a legal fixture of scandal-ridden Washington who has previously represented Bill Clinton, Jared Kushner and Ivanka Trump.

In a court filing on Sunday, Mr Lowell said prosecutors had “changed their decision on the fly” about a deal they still believed was “valid and binding”.

But Mr Weiss’ team has indicated the deal is dead and only a trial will now bring a fair resolution to the case.

In a court filing, they wrote that the agreement on the gun charge “never went into effect” and “none of its terms are binding on either party”.

They also called separately for the tax-related offences to be dismissed so that future charges can be brought in California or Washington DC.

Those two jurisdictions may have more scope to charge Hunter Biden’s tax violations, although Republicans contend that is a ploy to get the case before friendlier judges.

Questions have been raised over the past two decades about Hunter Biden’s business practices, and whether he had leveraged his name and access to his powerful father to make money and land clients.

Particular attention has been paid to what he was doing in China and Ukraine during Joe Biden’s vice-presidency.

In 2013, the younger Mr Biden became a founding board member at BHR, a private equity firm backed by some of China’s local governments and largest state banks.

He went on to a hold a 10% equity stake, although attorney George Mesires has claimed that Mr Biden did not acquire the stake until after his father’s tenure as vice-president ended in 2017. He remained with the board until 2020.

In 2014, Mr Biden joined the board of Burisma, a Ukrainian natural gas company where he made about $1.2m per year.

His father was at the time engaged in anti-corruption work as the Obama administration’s point man on US-Ukraine relations.

The elder Mr Biden argued the country’s top prosecutor Viktor Shokin was blocking corruption investigations and he rallied the international community to push for his ouster.

But Republicans allege Mr Shokin, who was removed by parliament in 2016, was fired because he was investigating Burisma.

The president has long maintained he never discussed business with his son or his associates.

But Devon Archer, a long-time business partner, testified behind closed-doors to lawmakers that Mr Biden frequently put his father on speakerphone during calls with various contacts.

Congressman James Comer, who is leading the probe in the House of Representatives oversight committee, has alleged that the then-VP “was “the brand” sold to enrich the Biden family.

On 9 August, Mr Comer cited bank records obtained by his panel that he said showed the Biden family and its associates had reaped $20m from oligarchs in Russia, Kazakhstan and Ukraine during his vice-presidency.

Separately, Hunter Biden’s alcohol and drug abuse, and extramarital activity, has provided ample fodder for the tabloids – and at least some measure of pain to his family.

In 2019, a DNA test confirmed that, despite his repeated denials, Hunter Biden had fathered a child with an Arkansas woman who filed a paternity suit against him.

Lunden Alexis Roberts has since settled that suit, with her child – Navy, now 4 – receiving an undisclosed amount in monetary child support as well as some of Mr Biden’s paintings.

Ms Roberts also agreed to drop a previous effort to have her daughter’s last name changed to Biden.

Amid pressure from US media, President Biden was forced to acknowledge his seventh grandchild for the first time late last month.