Hunter Biden went from ‘sweetheart deal’ to ‘poison pill:’ legal experts break down derailed plea deal

President Biden's son left federal court Wednesday after his pre-arranged plea deal with the Justice Department (DOJ) fell apart after surprising revelations that Hunter Biden is still under investigation for possible Foreign Agents Registration Act (FARA) crimes. 

Hunter Biden was expected to plead guilty to two misdemeanor tax counts of willful failure to pay federal income tax as part of a plea deal to avoid jail time on a felony gun charge.

But Judge Maryellen Noreika did not accept the plea agreement, questioning its constitutionality and the broad immunity Hunter Biden would have received, leading Hunter Biden to plead "not guilty" instead.

Criminal prosection experts say that the younger Biden went from "a sweetheart deal" to a "real poison pill" that could "expose him across the board."

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"The judge had an obligation to make sure that the defendant and the government have a very clear idea of what is implicated guaranteed," Jonathan Turley, criminal law professor at George Washington University, told Fox News, adding that "they didn't have that."

Turley said the plea deal dissolving in such a manor is "extremely rare" akin to "a wedding where both the groom and bride object."

Hunter Biden, 53, has been under federal investigation since 2018. That investigation into his "tax affairs" began amid the discovery of suspicious activity reports that related to money from "China and other foreign nations." IRS whistleblowers said the investigation began as an offshoot from an existing probe into a foreign pornography platform.

Hunter was expected to plead guilty to two misdemeanor counts of willful failure to pay more than $1 million in federal income tax in exchange for immunity from other crimes.

He was also expected to enter into a pretrial diversion agreement for a separate felony charge of possession of a firearm – an element of which Noreika expressed questions of constitutionality.

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Turley said the "sweetheart deal" was an effort to "cap off" the years-long federal probe into Hunter Biden's taxes and foreign business dealings. "But now, it’s the worst possible situation for Hunter Biden," Turley said.

Turley said Biden "doesn't have any protection at all" and that the Department of Justice is in a position where they can bring to bear any or all of the remaining counts, including FARA.

"And they usually do," Turley said. When a defendant "goes south" on a plea deal, the DOJ usually "puts everything on the table for a potential trial."

Jim Trusty, criminal prosecutor and former lawyer for former President Donald Trump, said the plea deal breakdown was unusual.

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"Up until today, Delaware was looking like the place where investigations go to die," Trusty told Fox News Digital.

But DOJ attorneys reiterated to the judge that there is an "ongoing investigation" surrounding Hunter Biden.

At one point the judge asked DOJ prosecutor Leo Wise, "Is there an ongoing investigation here?"

Wise answered that "there is" but said he couldn’t tell the judge what the investigation was into. When she asked if the government could potentially bring a FARA charge, Wise answered, "Yes."

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"What we found out from statements that DOJ lawyers made in open court is that Hunter is still under investigation, that he faces potential liability and that there was nothing in the plea deal or offer that would provide him with immunity against future prosecution on those grounds," former federal prosecutor Will Scharf told Fox News Digital.

Scharf said that a likely next-step scenario is that a new plea deal will be put in place that will be limited to crimes within the jurisdiction of the District of Delaware, namely the tax crimes, gun and drug charges.

"I think Hunter is just going to have to eat that and accept that he will continue to be under investigation for FARA," he said. 

"Hunter is not out of the water. He is in a lot of trouble. And the situation is going to continue to develop. Today was, I think, in Hunter's mind, supposed to be the end. And instead, he found out he's really pretty close to the beginning," Scharf added.

Fox News Digital's Brooke Singman contributed to this report.