Hunter Biden’s sister-in-law has testified at his criminal trial she found remnants of crack cocaine and a gun in his truck, potentially bolstering prosecutors’ case that US President Joe Biden’s son broke a law barring drug users from owning firearms.

The jury in the first criminal trial of a US president’s child has heard testimony this week from witnesses including his ex-wife and a former girlfriend about 54-year-old Hunter Biden’s past prolific drug use, which he has publicly acknowledged.

Hallie Biden, the widow of Hunter Biden’s brother Beau Biden – who died of cancer in 2015 – testified she often cleaned out Hunter Biden’s truck, searching for drugs, in an attempt to help him get his life in order.

She told the jury that she found drug paraphernalia and a Colt Cobra .38-calibre revolver during one of those searches, and feared Hunter Biden or her children would find the gun and hurt themselves.

“I panicked and wanted to get rid of it,” said Hallie Biden, who said she struck up a romantic relationship with Hunter Biden beginning late 2015 or early 2016.

She told the jury how she took the gun from his truck, the last time Hunter Biden had possession of the gun, and threw it in a rubbish bin at a nearby gourmet food store.

Federal prosecutor Derek Hines said the government could call its last witness on Thursday. 

Hunter Biden and his lawyers have not said if he will testify in his own defence, a risky move that most criminal defendants avoid because they expose themselves to questions from prosecutors.

Hunter Biden has pleaded not guilty to three felony charges accusing him of failing to disclose his use of illegal drugs when he bought the gun in October 2018 and of illegally possessing the weapon for 11 days.

He told the judge in the case at a 2023 hearing that he had been sober since 2019.

Defence lawyer Abbe Lowell told jurors during opening statements that Biden was not using drugs when he purchased the gun and did not intend to deceive because he did not see himself as a drug user at the time.

If Hunter Biden is convicted on all charges, he faces up to 25 years in prison although defendants generally receive shorter sentences, according to the US Justice Department.

The US president said on Thursday he would not pardon Hunter Biden.

In an interview with ABC News, President Biden replied “yes” when asked if he would rule out pardoning Hunter Biden. 

He also replied “yes” when asked if he would accept the outcome of the trial.