Judge Maryellen Noreika, in her initial instructions to jurors, explained how they are to apply the law to the facts of the case for the three criminal counts Hunter Biden faces.

"You must not attach any significance to the fact that the defendant did not testify," she read aloud in the courtroom, after the defense decided not to call Hunter Biden to the stand.

The judge defined "knowingly," the central term by which jurors must determine if Hunter Biden bought the gun at the center of the case "knowing" he was an addict or user of drugs, after he stated on the gun-purchase form that he was not.

Closing arguments are scheduled to begin at 12:05 p.m. ET, after which the judge will give the jury her final instructions and their deliberations will begin.

Closing arguments will begin at about noon ET after Hunter Biden chose not to testify in his federal gun case.

The defense rested without him taking the stand, after which prosecutors presented a brief rebuttal case, then the judge gave the jury their initial instructions.

Following the prosecution's rebuttal case, the judge read the jury their initial instructions.

Court is then expected to break for lunch, with closing arguments currently scheduled for the afternoon.

The judge will then give the jury their final instructions before they begin deliberations.

The government rested its rebuttal case after a brief cross-examination of FBI special agent Erika Jensen, who testified about location and text message data relevant to the case.

Attorneys then gathered for another sidebar conference.

Hunter Biden's former romantic partner Hallie Biden told jurors that Hunter Biden was "tired, exhausted, and looked like he hadn't slept" on the evening of Oct. 22 or early morning of Oct. 23, 2018, when he arrived at her home in Wilmington to sleep.

She observed that he "could've been" on drugs when she saw him -- just hours before she found his newly purchased Colt Cobra revolver in his car and discarded it in a dumpster.

"I went to clean out his car and his stuff" as he slept in her home, in hopes that when he awoke they could "start anew and deal with stuff," she testified, referring to his addiction to "both" drugs and alcohol.

The testimony didn't appear to be quite the smoking gun sought by prosecutors, who are trying to prove Hunter Biden was using crack at the time of his firearm purchase on Oct. 12 -- one of the central questions in the case.

Hallie Biden, who is the widow of Hunter Biden's late brother Beau Biden, testified that earlier in 2018 she also became addicted to crack after Hunter Biden introduced her to the drug -- but that she is now clean.

"It was a terrible experience I went through," she said, adding that she was "embarrassed and ashamed, and I regret that period of my life."