Hunter Biden’s attorneys on Tuesday doubled down on their arguments for dismissing federal gun charges brought against the president’s son.

In a series of court filings, Biden’s lawyers sought to bolster their positions for why a federal judge should toss out the charges brought in September that included an allegation that he possessed a firearm while using a narcotic.

They also responded to a recent filing by prosecutors that said “investigators observed a white powdery substance” on a brown leather pouch that held Biden’s firearm and that it was later identified as cocaine.

A member of Hunter Biden’s legal team told NBC News on Tuesday that authorities had the “smoking pouch” for five years before running tests and that the pouch evidence can’t be authenticated because it was widely handled before testing. Evidence provided from text messages also does not contain a single text suggesting drug use on the day Biden is alleged to have purchased the gun, the member of Biden’s legal team said.

The prosecution “has not alleged in the indictment that Mr. Biden was using unlawful drugs at the time he purchased the firearm,” his attorney’s wrote in one of Tuesday’s filings.

Special counsel David Weiss’ office declined to comment on the filings.

Weiss this month had opposed filings by Biden’s attorneys to dismiss the felony gun charges. In one filing, government attorneys had argued that any suggestion of a politically motivated prosecution was “meritless.”

An attorney for Biden said Tuesday that the prosecutors’ filings added fuel to his client’s argument that the charges should be dismissed on the basis of selective and vindictive prosecution, immunity, and constitutional grounds and argued that Weiss was unlawfully appointed to oversee the case.

“The filings made by the prosecutors provide more evidence that these charges result from a politically motivated attack instigated by former President Trump and his MAGA allies,” Abbe Lowell said in a statement.

“This pressure caused the prosecutors to violate their own non-prosecution agreement, the DOJ’s own regulations for how they should have been appointed, and the Constitution to pursue them,” he added.

Biden’s attorneys argued in one of the filings that Weiss’ work as U.S. Attorney for Delaware rendered him ineligible to serve as special counsel because of regulations governing independence from the federal government.

“If someone who was not properly appointed or licensed as a prosecutor brought an indictment, the only remedy for the person charged would be to invalidate the charges,” they wrote.

In another filing, Biden’s team highlighted an appeals court ruling on firearm possession that they said could provide constitutional grounds for dismissal of the gun charges and urged delaying the case from proceeding to trial until the Supreme Court weighs in on that matter.

Biden’s attorneys also reinforced their arguments that Biden’s indictment should be dismissed due to immunity that was conferred to him last year through what’s known as a diversion agreement, suggesting that “the prosecution now faces political pressure to find some way to squirm out of the Agreement that it has signed.”

Prosecutors had previously argued that probation’s approval was a “necessary condition precedent” for the contract to be effective.

Biden has pleaded not guilty to the gun charges.

In addition to the gun charges, Biden is also facing tax-related charges in California, including three felony counts. He pleaded not guilty this month.

House Republicans have targeted Biden in their impeachment inquiry into his father. After initially defying a congressional subpoena that requested a closed-door deposition, Biden is now expected to appear for a closed-door deposition with the House Oversight and Judiciary panels on Feb. 28.