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.

On redirect examination of FBI Special Agent Erika Jensen, prosecutor David Hines heavily pushed back on the defense's suggestion that no text messages showed Hunter Biden buying drugs during the time he purchased a gun, and their contention that his large cash withdrawals could have been for other purposes.

Hines returned to the key text message Hunter sent while he owned the gun, telling his then-partner Hallie Biden that he was "sleeping on a car" smoking crack.

"You understand what that means, right?" Hines asked the FBI agent.

"Yes," she responded.

"Crack is crack," Hines said.

Hines then returned the issue of Hunter Biden's large cash withdrawals -- over $150,000 in three months -- pushing back on the suggestion from the defense that he used the cash to pay for other things, such as Airbnb rentals.

Hines displayed bank records that showed Hunter paid for Airbnb rentals with a Visa check card.

Hines also pointed out that when Hunter Biden bought alcohol, he did so with a credit card instead of cash -- making the point that drug dealers generally favor cash transactions.

Hunter Biden's attorney, Abbe Lowell, questioned FBI Special Agent Erika Jensen about Hunter Biden's infamous laptop, which prosecutors entered into evidence yesterday, asking her on cross-examination if she had done an "analysis" of whether "data" or "content" of the laptop was "tampered with, added to, or subtracted" during the months that passed between when Hunter Biden dropped off the device for service in April of 2019 and when the FBI obtained it in December 2019.

Jensen said she had not.

Lowell also took aim at the numerous text messages prosecutors have presented as evidence of Hunter Biden's drug addiction in 2018 and 2019.

Lowell showed that only two messages among the several alluding to drug use, drug paraphernalia, and drug purchases occurred during October of 2018 -- the period during which Hunter Bidden procured the firearm. The rest were either other months before the incident or months afterward, Lowell showed.

"You don't see any references … to baby powder?" Lowell asked Jensen, before ticking through other drug terms that appeared in the messages earlier in 2018 or later in 2019, including "chore boy" and "party favors."

Each time, Jensen replied "No."

Lowell also questioned Jensen about two messages Hunter Biden sent around the time of his gun purchase that did allude to drug use, one of them referring to an alleged drug dealer named "Mookie" and other referencing "smoking crack on a car" in Wilmington. Lowell sought to establish that Jensen had no firsthand knowledge about the contents of the messages.

"Do you know if there is a person named Mookie?" Lowell asked.

"No," Jensen replied.

"Do you know if he was on a car smoking crack?" Lowell asked later, referring to Hunter Biden.

"No," Jensen said.

Lowell subsequently ended his cross-examination of Jensen, and prosecutors undertook their redirect examination.

On cross-examination, defense attorney Abbe Lowell asked FBI Special Agent Erika Jensen about the timeline of the text messages, photos, and chapters of Hunter Biden's memoir to argue that his client was not using drugs during the time of the gun purchase.

Lowell showed the jury bank statements that chronicled a series of alcohol purchases made by Hunter Biden in the days leading up to the gun purchase and after, suggesting that he was consuming alcohol and not recreational drugs.

Jensen also testified that several of the photos prosecutors showed the jury of drug substances and what appeared to be a crack pipe were taken months after the gun purchase.