Another historic U.S. trial, this time of Biden's son Hunter

Jury selection begins Monday in the gun trial of Joe Biden's son Hunter, the first prosecution in U.S. history for the child of a sitting president -- just as the Democratic leader seeks to accelerate his reelection campaign.

The case comes on the heels of another unprecedented trial, in which White House hopeful Donald Trump became the first former U.S. president convicted of a crime, and Republicans are keen to distract from their front-runner's legal woes.

The 54-year-old Hunter Biden denies three felony counts stemming from his purchase of a .38-caliber Colt Cobra revolver in 2018 when, by his own admission, he had been heavily addicted to drugs.

The Yale-trained lawyer and lobbyist-turned-artist has been plagued by legal troubles and controversies, mostly connected to alcoholism and crack cocaine addiction, that have dragged on his father's campaign.

He will be tried in the family's hometown of Wilmington, Delaware, on two counts of making false statements on gun purchase paperwork that he was not using drugs illegally.

He faces a third charge of illegally possessing the gun -- which he had for only 11 days in October 2018.

Hunter Biden nearly escaped prosecution. But last July, a plea bargain fell apart.

If found guilty, Biden could face 25 years in prison, though in practice such offenses, if not accompanied by other charges, are seldom punished by incarceration.

- 'Rehabilitation' -

Jurors will hear about the defendant's drug use as prosecutors run through events that led to him buying the firearm in Delaware.

The defense team has pushed for narrow definitions of the terms "addict" and "user," and requested instructions requiring an acquittal if the jury determines that the defendant did not consider himself to fit those definitions.

"The terms 'user' or 'addict' are not defined on the form and were not explained to him," his lawyer Abbe Lowell wrote in court documents.

"Someone, like Mr. Biden who had just completed an 11-day rehabilitation program and lived with a sober companion after that, could surely believe he was not a present tense user or addict."

Among those reportedly expected to testify is the defendant's lover at the time of the firearm incident: Hallie Biden, the widow of Hunter's brother Beau Biden.

The case comes with Republicans pursuing an impeachment inquiry in Congress into what they claim is a Biden family criminal conspiracy, although they have provided no evidence.

Republican lawmakers have accused Hunter Biden of engaging in corrupt business practices in China and Ukraine, but he has not been charged with any crimes related to his foreign dealings.

The president has said he stands by his son and loves him for his attempts to recover from drug addiction.

Democratic congressman Adam Schiff, a Biden ally, told CNN Sunday that Americans should "absolutely" respect the jury's verdict, however it rules.

"And I think the president himself will respect the verdict -- much as it is painful, I'm sure, to see one of your children on trial."

Prosecutors have said they expect to take three days to present their case, and the untelevised trial will likely last about two weeks.

Hunter Biden faces separate tax evasion charges in California, in a case set for trial later this year.

Last week Trump was convicted in a Manhattan court of 34 counts of falsifying business records to cover up hush money paid to an adult film star.