Hunter Biden has arrived at the courthouse for the start of his federal gun trial this morning.

His stepmother, first lady Jill Biden, is attending the proceedings.

Two hundred and fifty Delaware residents have been summoned to the courthouse in downtown Wilmington, where they will face typical questions about their fitness to serve as jurors.

But because this is the trial of the son of a sitting president, there will be some novel topics covered during the jury selection process known as "voir dire."

Among the questions jurors will be asked: "If you were eligible to vote in any election(s) in which Joseph R. Biden was a candidate, would that fact prevent you from maintaining an open, impartial mind until all of the evidence is presented, and the instructions of the Court are given?"

And "Do you believe Robert Hunter Biden is being prosecuted in this case because his father is the President of the United States and a candidate for President?"

On the eve of trial, U.S. District Judge Maryellen Noreika threw a wrench in one of the key arguments attorneys for Hunter Biden were planning to advance, ruling that an annotated copy of the federal form Hunter Biden is accused of lying on would be excluded from evidence.

The original document, called an ATF Form 4473, was created in 2018 when Hunter Biden purchased the firearm. But in 2021, gun store employees made a copy that included some handwritten notes. Defense attorney Abbe Lowell contended that employees had "tampered with" the document, and that it raised questions about "who wrote what on the form, and when."

Lowell hoped his argument would undermine the credibility of some key government witnesses -- the people who sold Biden the gun -- and potentially create a reasonable doubt that Hunter Biden was the one who actually checked that box.

Attorneys for special counsel David Weiss' office have said the gun shop employees merely "annotated" the form and urged Noreika to prevent Lowell from introducing it into evidence.

Late Sunday, Noreika sided with Weiss.

Jury selection is scheduled to get underway today in the federal gun trial of Hunter Biden, who authorities say broke the law when he purchased a Colt revolver in 2018.

President Joe Biden's son faces two counts of making false statements while purchasing the firearm and a third count of illegally obtaining it while addicted to drugs.

Although the charges together carry a possible sentence of up to 25 years, legal experts say that, as a first-time and nonviolent offender, Hunter Biden would not likely serve time if convicted.

The trial, in Delaware federal court, is expected to last two to three weeks.

Attorneys for Hunter Biden, in their cross-examination of FBI Special Agent Erika Jensen, attempted to push back on prosecutors' contention that Hunter Biden was abusing drugs at the time he said on a gun-purchase form that he was drug-free.

A key piece of evidence comes from Hunter Biden's 2021 memoir, in which he described his "relapse" just weeks after leaving rehab in August -- just six weeks before purchasing the firearm.

"I stayed clean for two weeks then relapsed," Hunter Biden wrote in his book.

Defense attorney Abbe Lowell, on cross-examination, questioned the assumption that Hunter Biden's relapse implied that he was referring to his drug use -- suggesting instead that he was referring to his alcohol addiction.

"When he was referring to that in his book, was he talking about relapsing to drugs and alcohol, or do you know what he meant?" Lowell asked.

"I can only state what was stated," Jensen said.

"Which is, 'Then I relapsed?'" Lowell asked.

"Just what it says, 'I relapsed,'" Jensen replied.

Jensen also acknowledged that she could not verify that Hunter Biden was continuously using drugs from 2015 to 2019, saying, "My recollection is that there are excerpts where he was principally occupied with smoking crack cocaine. I didn't get the sense that it was the entire history."

"Meaning that there were periods of time that he was not?" Lowell asked.

"I think there -- including the period in August where we have some invoices for rehab, that there were periods where there was not," Jensen said.

It was an important moment for the defense, as Lowell managed to establish that Hunter Biden's use of drugs was not consistent -- cuing up his argument that the president's son was not on drugs at the time of his firearm purchase.

Prosecutors also entered into evidence records related to enormous cash withdrawals Hunter Biden made -- more than $150,000 from September through November of 2018, including a $5,000 withdrawal on the day he purchased the gun. Prosecutors suggested this cash was used to procure drugs; Lowell, on cross-examination, established that Hunter Biden paid $900 in cash for the weapon and accessories.

Court was subsequently recessed for the day, with Lowell's cross-examination of Jensen scheduled to resume Wednesday morning.

Prosecutors suggested that Hallie Biden would be the next witness after Jensen, making it likely that the first Biden family member to testify will take the stand at some point tomorrow.