Hallie Biden, Hunter Biden's former romantic partner who is the widow of his brother Beau Biden, has taken the stand as the prosecution's next witness.

Prosecutors have said they expect her to testify about Hunter Biden's drug at the time of his gun purchase in October 2018.

Before gun store clerk Gordon Cleveland stepped off the stand, he testified that Hunter Biden did not exhibit any symptoms of drug or alcohol abuse when he purchased the gun at the center of the case.

When asked by defense attorney Abbe Lowell if Hunter Biden exhibited any symptoms at the time of his gun purchase, such as being "glassy eyed" or smelling of alcohol, Cleveland replied, "None at all."

Cross-examining gun store clerk Gordon Cleveland, defense attorney Abbe Lowell asked about the framing of the various questions on the gun form that Hunter Biden is accused of lying on -- including the difference between "have you" and "are you."

The form, for example, asks the applicant if they "have ever" been convicted -- but asks "are you" an unlawful user of drugs.

The defense team has used this to argue that Hunter Biden could have reasonably believed he was not violating any laws when he checked "No" on the drug-use box, because they say he was not currently using drugs.

"It does not say, 'Have you ever,"' Lowell said.

In court today, Hunter Biden has been attentive and focused, watching as attorneys clashed earlier over evidence. He gripped his pen as prosecutor Leo Wise asked the judge to keep out texts that his team wishes to use when they cross-examination Hallie Biden.

Special counsel David Weiss, who brought the case, has been seated in the front row behind his prosecution team, periodically nodding along as they make their arguments.

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.

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.