Hallie Biden, the widow of President Joe Biden's late son Beau Biden, testified as a key government witness at Hunter Biden's federal gun trial on Thursday, recounting in excruciating detail the "terrible experience" of Hunter Biden's drug addiction in the months leading up to her discovery of a firearm in his vehicle.
Prosecutors hope the testimony of Hallie Biden, who was Hunter Biden's romantic partner at the time, attests to Hunter Biden's drug use in October of 2018, when prosecutors say Hunter Biden lied on an ATF form when he said he wasn't using drugs at the time he purchased the firearm. The president's son has denied the charges.
MORE: Hunter Biden gun trial updatesProsecutors, who later called several witnesses to testify about the recovery of the gun after Hallie Biden threw it away in a trash can, plan to call two additional witnesses on Friday before resting their case.
Here are the four big takeaways from Day 4 of the trial.
When Hallie Biden found a Colt Cobra revolver, a speedloader and bullets in Hunter Biden's vehicle, on Oct. 23, 2018, she said she "panicked."
"I wanted to get rid of them," she told the jury.
Hallie Biden, who offered a detailed account of the day she found and later discarded the weapon, testified that along with the gun she found "remnants" of crack in Hunter Biden's vehicle -- but acknowledged under cross-examination that the drug traces could have been there for weeks or months.
When Hunter Biden learned that Hallie Biden disposed of the weapon, he was "angry," she said.
"It's hard to believe anyone is that stupid," Hunter Biden texted her.
"I'm sorry," Hallie texted Biden at one point. "I just want you to be safe. That was not safe ... and it was open unlocked and windows down and the kids search your car."
Jurors were shown several surveillance videos of Hallie Biden throwing the gun away and going into the grocery store, then returning later that morning to search for the firearm.
Hallie Biden testified that Hunter smoked crack and exhibited changes in behavior -- including being "agitated" and "high-strung" -- but also spoke of his ability to "function" on the drug.
He used it "frequently -- daily," she said.
But under cross-examination from defense attorney Abbe Lowell, Hallie Biden conceded that "it's difficult to recall" exactly where Hunter was at specific moments or whether he was where he suggested he was, at one point saying that "it's all kind of vague."
She told the jury that for most of the month of October 2018 she did not see Hunter Biden abusing drugs or alcohol -- potentially undercutting the prosecution's contention that he was using drugs at the time he purchased the gun on Oct. 12.
Former Delaware State Police lieutenant Millard Greer described tracking down the gun after Hallie Biden had thrown it in the trash outside the supermarket.
Greer said he reviewed surveillance footage, interviewed witnesses, and ultimately retrieved the weapon from Edward Banner, who was known to "rummage through trash."
Greer said Banner had placed the firearm in a sock along with a leather pouch containing the gun.
Banner, called as the government's last witness of the day, corroborated much of Greer's account, testifying he'd found the gun in a trash can outside the grocery store, stored it on a top shelf at home, and ultimately turned it over to Greer.
Prosecutors said before court concluded on Thursday that they have two witnesses left -- a DEA drug specialist and an FBI chemist -- and that they intended to rest their case on Friday morning.
Defense counsel said they would call two or three witnesses and would likely rest their case by the end of the day on Monday. As Lowell previously suggested, he may call James Biden, the president's brother, and Naomi Biden, the president's eldest granddaughter.
Lowell said he was still unsure whether Hunter Biden would testify in his own defense.