Hunter Biden's ex-girlfriend has testified that she "panicked" when she searched his car and found a gun - a moment that set off a chaotic string of events that has brought the president's son to a federal courtroom.
Hallie Biden, who is also the widow of the defendant's late brother Beau, said she had discovered the revolver amid piles of clothes and litter in the glove compartment of Hunter Biden's truck.
Ms Biden, 50, also told the court she was "embarrassed and ashamed" to have started smoking crack cocaine herself after Mr Biden, 54, introduced her to the drug.
It is the first trial for the son of a sitting US president. He could face up to 25 years in prison if found guilty.
Hunter Biden has pleaded not guilty to three charges related to his possession of a firearm while allegedly using narcotics.
He is accused of knowingly lying on federal paperwork when he purchased the revolver and ammunition from a gun shop in Wilmington, Delaware, on 12 October 2018.
His defence team says he was in recovery at the time, so was truthful when he indicated on the paperwork that he was not a drug user.
On Thursday, the court heard from Hallie Biden, a central figure in the case who became romantically involved with the defendant shortly after the 2015 death of his brother and her husband.
In often emotional, detailed testimony, she spoke of the pair's "volatile" and "off-on" relationship, as well as their struggles with drug use and agonising battles to recover.
Concerned after seeing Mr Biden looking "exhausted" and fearing he could have relapsed into crack use, Ms Biden told jurors she had searched his truck early on the morning of 23 October 2018 - something she had frequently done.
There, among piles of clothes and garbage, she had found "remnants" of crack cocaine as well as drug paraphernalia.
“Oh, and the gun, obviously," she added.
Almost instantly, she recalled, panic set in.
"I didn't want him to hurt himself, and I didn't want my kids to find it and hurt themselves," the mother-of-two said.
"I was afraid to kind of touch it. I didn't know it was loaded," Ms Biden added.
Fearful, she wrapped the .38 calibre Colt Cobra revolver into a leather pouch, stuffed it into a purple "little gift shopping bag" and drove to a nearby grocery store, where she threw it in a rubbish bin.
"I realise it was a stupid idea now," she said. "But I was panicking."
Initially, she did not plan to tell Mr Biden about what she had done. But when he woke up that morning, he realised it was missing.
"Did you take that from me Hallie," read one angry text shown to jurors. "You really need to help me think right now, Hallie. This is very serious."
At his urging, she returned to the store to find the gun but was unable to. She then filed a police report.
"I'll take the blame," she texted him from the scene. "I don't want to live like this."
It has previously emerged that the weapon was discovered by a man who often rummaged through the grocery store’s refuse to gather recyclable items.
Ms Biden also told the court that she had not see Mr Biden use crack cocaine in the days leading up to him buying the gun and her disposing of it.
As she testified, Hunter Biden appeared to look intently in her direction.
He also looked back at his wife, Melissa Cohen Biden, who has attended each day of the trial so far.
Hallie Biden also told the court that it was only after their relationship began that she had learned of Mr Biden's drug use.
She found crack cocaine at her house - where he would frequently stay - and later repeatedly saw him use the drug.
Crack, she said, left him "agitated or high-strung, but at other times, functioning as well".
She also testified that she had fallen into using crack cocaine herself after he introduced her to the drug.
"It was a terrible experience that I went through, and I'm embarrassed and ashamed, and I regret that period of my life," she said.
Ms Biden testified that she had stopped using the drug in August 2018, but that he had continued to use.
The prosecutor asked on Thursday about a text message Hunter Biden had sent to Ms Biden the day after he bought the gun, saying he was waiting for a dealer named Mookie.
She told the court that had meant "he was buying crack cocaine".
Two days after the gun purchase, he texted Ms Biden that he was "sleeping on a car smoking crack".
The series of texts also included several emotional messages from Ms Biden in which she pleaded with him to get sober.
"I'm afraid you're going to die," one message read.
The defendant's lawyers explained the texts by suggesting their client had been lying about drug use to avoid seeing Hallie Biden - noting that she had had no way of knowing what he was actually doing at the time.
During cross-examination, Ms Biden confirmed she had not seen him using drugs around this time.
Abbe Lowell, Mr Biden's attorney, asked her whether the request to "help me get sober" could have also referred to alcohol - to which she agreed.
The prosecution's case, however, rests on convincing jurors that he was an addict.
Ms Biden's testimony was followed by Millard Greer, a former Delaware State Police lieutenant who recovered the weapon, as well as Edward Banner, an 80-year-old pensioner who found the weapon while looking for recyclables in the grocery store's bins.
The prosecution is expected to call two more witnesses, including an FBI expert and a DEA agent, before resting its case.
The defence team expects to call two or three witnesses before resting its case.
Mr Lowell said that no final decision had been made on whether Mr Biden would testify.
As his son appears in court, President Joe Biden has continued his public duties. On Thursday, he delivered a speech in France to mark the 80th anniversary of D-Day.
In an interview with ABC News on the same day, Mr Biden said he would accept the outcome of his son's trial and would not pardon him if convicted.
Hunter Biden also faces a trial in California in September on charges of failing to pay $1.4m (£1.1m) in taxes.
