Washington — Hunter Biden's top criminal defense attorney filed a motion on Tuesday asking to depart the first son's legal team in Delaware weeks after a plea agreement he had negotiated with federal prosecutors fell apart, according to newly filed court documents. That breakdown precipitated Attorney General Merrick Garland's decision last week to elevate the U.S. attorney handling the matter to special counsel status.

Christopher Clark sought permission Tuesday from a federal judge to withdraw from Hunter Biden's defense, citing the possibility that the now-defunct plea agreement and other discussions with prosecutors could become the focus of a new legal dispute. 

"Based on recent developments, it appears that the negotiation and drafting of the plea agreement and diversion agreement will be contested, and Mr. Clark is a percipient witness to those issues," the motion filed by Biden's attorneys Tuesday said. "Under the 'witness-advocate' rule, it is inadvisable for Mr. Clark to continue as counsel in this case." 

The motion to remove Clark from the case states that because he was a witness to many of the disputed legal actions, he could no longer represent the president's son. By having Clark step away, Hunter Biden's legal team is signaling they plan to fight hard to keep in place broad immunity provisions contained in a signed diversion agreement, which they argue should survive the breakdown of the plea deal.

"There are no 'take backs' once the government signs it and delivers it to court," a member of Hunter Biden's team told CBS News. "The prosecutors are attempting to renege on a valid agreement that they initiated, negotiated and signed before submitting it to the Court last month."   

In a separate court filing on Tuesday, prosecutors pushed back on the Biden team's claims, arguing "the proposed diversion agreement never took effect," and characterized it as a "now-withdrawn" agreement. 

Federal prosecutors in Delaware and the defense team said in July that they reached tentative plea and diversion agreements on two misdemeanor tax and a felony gun charge respectively, but the deals quickly unwound in the final stretch when the judge handling the matter raised concerns about their terms in a legal drama that played out in open court last month. 

Hunter Biden ultimately pleaded not guilty to the three charges filed against him and prosecutors have said the investigation is ongoing. 

In subsequent court filings, prosecutors said the parties were "at an impasse" and that a trial was likely, as Hunter Biden's defense team alleged the government "reneged" on the agreements and argued the diversion agreement on the felony gun charge was signed and binding, a claim the government rejected on Tuesday.  

On the same day, prosecutors told the judge handling the case that negotiations between the parties continued into last week, but counteroffers were deemed insufficient. 

The move came a day after another attorney on Hunter Biden's legal team, Washington, D.C., lawyer Abbe Lowell, filed papers with the court to formally enter the case. Lowell, a veteran attorney who has represented a roster of high-profile clients, including Ivanka Trump and Jared Kushner, had been helping Hunter Biden navigate the ongoing congressional probe into his business dealings. 

Lowell told Margaret Brennan on "Face the Nation" this past Sunday that he did not view a trial as "inevitable."

"Withdrawal will not cause a substantial hardship to Mr. Biden because counsel from the other firms that have entered an appearance will continue to represent Mr. Biden in this matter," the Biden team's filing said. 

On Friday, Garland appointed Delaware U.S. Attorney David Weiss as special counsel in the matter after Garland said Weiss requested the elevation to handle the ongoing investigation into the president's son.

"As special counsel, he will continue to have the authority and responsibility that he has previously exercised to oversee the investigation and decide where, when, and whether to file charges," Garland said, reiterating Weiss' past statements that the investigation continues. 

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