With the strike of a judge's gavel in Delaware, Hunter Biden, the son of Joe Biden, became the first child of a sitting president to be a criminal defendant.
Prosecutors allege the younger Biden, 54, lied about his drug use on application forms when he purchased a handgun in 2018.
He faces up to 25 years in prison if convicted of the three federal counts, in a case that began on Monday with jury selection.
Mr Biden has pleaded not guilty to the charges.
The trial - which comes as his father campaigns for re-election - is likely to see prosecutors delve into graphic details of Mr Biden's crack cocaine addiction, potentially providing fodder for the president's political foes.
While he has repeatedly declined to comment on the court case, in a statement published on the morning of the trial's start the elder Biden said that he has "boundless love" and "confidence" in his son.
"Hunter's resilience in the face of adversity and the strength he has brought to his recovery are inspiring to us," the president added.
Here's what we know about the case.
What are the charges?
Mr Biden is facing three federal charges in the case: two counts of making false statements and one count of illegal gun possession.
The charges all relate to his purchase of a revolver at a Delaware gun store in October 2018, which he kept for about 11 days.
By Mr Biden's own admission, he was deep in the throes of a "full blown addiction" to crack cocaine at the time.
The two false statement charges stem from allegations that he lied about his drug use on a federally-mandated form when he purchased the weapon.
Specifically, prosecutors allege that he falsely claimed that he was "not an unlawful user of and addicted to any stimulant narcotic drug" when he purchased a Colt Cobra Special revolver.
The third count is related to his possession of a firearm while alleged to have been a drug user.
The gun was discarded and discovered at a grocery store in Greenville, Delaware, prompting an investigation that ultimately led investigators back to the forms.
How strong is the evidence?
To convict Mr Biden, prosecutors will have to convince jurors that he knowingly made false statements on the form in a bid to deceive the store that sold him the pistol.
Additionally, they will have to prove that Mr Biden was a drug user or addicted to drugs, and took possession of the gun despite knowing as much.
US District Judge Maryellen Noreika has already ruled that defence lawyers cannot argue that the prosecution can only get a guilty verdict by proving Mr Biden was using drugs on the day he bought the weapon.
Instead, in a pre-trial hearing, the judge agreed with prosecutors' argument that they need only prove that "unlawful use (had) occurred recently enough to indicate that the individual (was) actively engaged in such conduct".
In court filings made ahead of the trial's start, prosecutors suggested that they would rely, in part, on deeply personal text messages and other communications made while Mr Biden was in the throes of addiction.
In one such text message cited in court documents, Mr Biden refers to himself as a "liar and a thief and a blame and a user and I'm delusional and an addict unlike beyond and above all other addicts that you know".
The prosecution is also expected to rely on the testimonies of witnesses including ex-wife Kathleen Buhle and Mr Biden's ex-partner Hallie Biden - who is also the widow of Mr Biden's brother Beau.
Prosecutors will also be able to point to Mr Biden's own 2021 memoir, in which he detailed his experiences as a drug user who was "up twenty-four hours a day, smoking every 15 minutes, seven days a week".
"All my energy revolved around smoking drugs and making arrangements to buy drugs - feeding the beast," he wrote in the book.
While Mr Biden has himself been quiet about the trial, legal documents filed by his lawyers suggest that they will focus on how much Mr Biden was aware of his addiction at the end of the purchase, and on the quality of the evidence itself.
His primary attorney, Abbe Lowell, unsuccessfully sought permission from the court to call upon an expert witness who can testify about an addict's understanding of their substance abuse issues.
In an interview with the OceanNewsUK after Mr Biden's not guilty plea, South Texas College of Law Professor Dru Stevenson said that charges for illegal gun possession usually result in a "slam dunk case".
"I don't think there's any question that [Mr Biden] will be convicted."
The third charge, regarding Mr Biden's alleged possession of a firearm while a drug user, is considered unusual, as it can be hard to prove someone is a drug user and has a gun.
"It's just really rare that they would go after someone and prosecute them for this," Prof Stevenson said. "But this is a high-profile person and there's been members of Congress demanding he be prosecuted."
Infamous laptop could feature
Among the most prominent pieces of evidence at the trial is likely to be the information on Mr Biden's infamous laptop, which has been the focus of intense media speculation and focus from conservative news outlets.
The laptop has also been at the centre of unproven theories linking Mr Biden and his father to corruption, which they both deny.
Mr Biden's own lawyers have argued that the computer was tampered with before it fell into the hands of investigators.
The special counsel appointed to oversee the probes into Hunter Biden, David Weiss, has said that the tampering argument is a "conspiracy theory" with "no supporting evidence."
In a May filing, prosecutors wrote that the laptop contained "significant evidence" of Mr Biden's guilt.
Could he go to prison if convicted?
The two false statement charges each carry a maximum sentence of up to 10 years, while the third count is punishable by up to five years - meaning that Mr Biden could face up to 25 years in prison if convicted.
Actual sentences for federal crimes, however, are typically less than the maximum penalties specified by law.
If Mr Biden is convicted, the judge in the case will ultimately determine the sentence after considering sentencing guidelines and a variety of other legal factors.
Hunter Biden's other charges
In addition to the gun charges in Delaware, Mr Biden is facing separate federal charges in California over allegations that he evaded a tax assessment, failed to properly file and pay taxes and filed a fraudulent tax return.
Several months after the spectacular collapse of a plea deal that would address both sets of charges last year, Mr Biden also pleaded not guilty to the tax charges.
