Gordon Cleveland, the gun store clerk who sold Hunter Biden the firearm at the center of the case, returned to the stand.

Cleveland was being cross-examined by the defense after testifying for the prosecution yesterday.

Hallie Biden, Hunter Biden's former romantic partner who is the widow of his brother Beau Biden, is expected to be the next witness following Cleveland.

Court resumed this morning with a sidebar conference.

Prosecutors and defense attorneys were arguing before the judge about an exhibit the defense wants to introduce when Hallie Biden, Hunter Biden's former romantic partner, takes the stand as expected later today.

Separately, defense attorney Abbe Lowell signaled his intention to file a motion to have the case thrown out after the government rests.

The long-shot bid will be filed on grounds of constitutional shortcomings and insufficient evidence, Lowell said.

Lowell also said his witnesses -- which could include President Joe Biden's brother James Biden and Hunter Biden's daughter Naomi Biden -- may not be available until Friday morning.

Hunter Biden has arrived at the Wilmington courthouse for today's proceedings.

Like previous days, he was accompanied by his wife, Melissa Cohen Biden.

The gun store clerk who sold Hunter Biden the handgun at the center of the government's case returns to the witness stand this morning on Day 4 of the trial as prosecutors look to wrap up their case against the president's son.

Prosecutors said at the end of Wednesday's proceedings that they plan to call six more witnesses -- including Hallie Biden, perhaps their most crucial witness -- before resting their case, which could happen as soon as this afternoon.

Defense counsel have leaned into their claim that Hunter Biden was not actively abusing drugs in October of 2018, the month of his gun purchase, and therefore did not knowingly lie on the federal firearm application form.

Zoe Kestan, one of Hunter Biden's ex-girlfriends, testified Wednesday that she witnessed him smoking crack the month before and the month after his gun purchase, but had "no idea" what he was doing in October.

To fill that gap, prosecutors plan to call Hallie Biden, his brother's widow with whom Hunter Biden was romantically involved.

"The evidence will show that during those 11 days, the defendant continued to use drugs and to talk about his drug use with Hallie," prosecutor Derek Hines said.

In the first exhibits presented in the government's case, prosecutors played excerpts from the audiobook of Hunter Biden's 2021 memoir "Beautiful Things" -- in which jurors heard in his own words about some of the most personal low points of his yearslong addiction to crack cocaine.

FBI Special Agent Erika Jensen, the government's first witness, introduced about a dozen audio excerpts played out over an hour, as Hunter Biden's voice boomed over the courtroom's loudspeakers while his stepmother, first lady Jill Biden, and several other members of his family sat in attendance.

"I used my superpower of finding crack cocaine anytime, anywhere," Hunter Biden said of the year 2018 -- the same year he purchased the gun that prosecutors say he lied to get. The audio contained passages in which he spoke about the darkest and most dangerous moments of his addiction -- at one point doing cocaine in the bathroom while on a graduation trip with his daughter. .

Jill Biden and her daughter Ashley Biden sat shoulder-to-shoulder as the clips played out, at times leaning their heads against one another. At one point, as Hunter Biden's voice was heard describing a raucous 12-day bender in Los Angeles, Jill Biden lifted her left arm and draped it around Ashley's shoulders.

A person sitting with the family told ABC News they were both "fighting off tears."

Hunter Biden, for the most part, stared intently into the nearby monitor displaying the book's contents, at one point slightly nodding along as he reheard some of his most painful struggles. The jurors appeared largely engaged, with many taking notes and looking up at the screen to follow along.