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.

Taking the stand as a prosecution witness, Hunter Biden's ex-wife Kathleen Buhle described how, after 25 years, their marriage deteriorated under the weight of his drug and alcohol addiction.

Buhle said she first learned of Hunter Biden's crack addiction when she discovered an empty crack pipe in an ash tray on their side porch the day after their anniversary in 2015. Hunter Biden was kicked out of the Navy in 2014 for testing positive for cocaine, and Buhle said ever since then she was "worried, scared" he would abuse drugs again.

When he was on crack, Buhle testified, "He was not himself … angry, short-tempered, acting in ways he wouldn't when he was sober."

She said she would find drug "remnants in little bags" and drug paraphernalia like "a broken crack pipe" -- often enough that she would search his car before allowing her daughters to use it.

In what could be a blow to one of Abbe Lowell's lines of defense, Buhle said Hunter Biden frequently interacted with friends and family, worked, and socialized while under the influence of crack cocaine -- and would often try to hide it from those close to him.

"Did you see him, for lack of a better word, function?" prosecutor Leo Wise asked.

"Yes," Buhle confirmed.