Hunter Biden, the president’s son, was charged on Thursday by federal prosecutors with lying about his drug use when he purchased a handgun in 2018 and with illegally possessing the weapon, setting up the potential for a trial coinciding with his father’s re-election campaign.
The indictment came as House Republicans stepped up their efforts to use Hunter Biden’s work abroad to build a case for impeaching President Biden. And it puts the Biden Justice Department in the remarkable position of prosecuting cases against both the president’s son and former President Donald J. Trump, the current front-runner for the Republican Party’s 2024 presidential nomination.
The gun charges are related to whether Mr. Biden had lied on a federal government form that he was required to complete when he purchased a .38 handgun in Delaware in 2018.
In response to a question on the form about whether he was using drugs, Mr. Biden had said he was not — an assertion that prosecutors concluded was false. Mr. Biden has publicly acknowledged his struggles with addiction to crack cocaine and alcohol and had been in and out of rehab around the time of the gun purchase.
The indictment returned by a federal grand jury in Wilmington, Del., charged Mr. Biden with three felonies: lying to a federally licensed gun dealer, making a false claim on the federal firearms application used to screen applicants and possession of an illegally obtained gun for 11 days, from Oct. 12 to Oct. 23, 2018.
“Hunter Biden possessed a firearm while knowing he was an unlawful user of or addicted to any stimulant, narcotic drug or any other controlled substance, in violation of federal law,” prosecutors charged in the five-page filing.
The gun was found by Hallie Biden, the widow of his brother, Beau, soon after its purchase. Hallie Biden, with whom Hunter Biden was having a romantic relationship at the time, threw the gun in a dumpster, claiming she was concerned that he might use it to take his own life.
If convicted, Mr. Biden could face up to 25 years in prison and $750,000 in fines. But nonviolent first-time offenders who have not been accused of using the weapon in another crime rarely get serious prison time for the charges.
No date has yet been set for his arraignment.
Abbe Lowell, Mr. Biden’s lawyer, has argued that the indictment should be thrown out, saying that the lead prosecutor on the case, David C. Weiss, is still legally bound by the previous diversion agreement and accusing Mr. Weiss of caving to the pressure from Trump supporters who had called the plea agreement a sweetheart deal.
“Hunter Biden possessing an unloaded gun for 11 days was not a threat to public safety, but a prosecutor, with all the power imaginable, bending to political pressure presents a grave threat to our system of justice,” he said in a statement.
The White House declined to comment.
The decision to file criminal charges against President Biden’s troubled younger son was an extraordinary step for the Justice Department and Mr. Weiss, whom Attorney General Merrick B. Garland named as a special counsel last month. Mr. Garland gave Mr. Weiss that status after the last-minute collapse of a previous deal that would have resolved the long-running investigation without Mr. Biden serving prison time.
The defunct deal also would have resolved an investigation into Mr. Biden’s late filing of his tax returns for several years. Prosecutors did not file tax charges against Mr. Biden on Thursday but could still do so.
Mr. Weiss’s team has also signaled that it continues to investigate other elements of Mr. Biden’s business activities, most likely including whether any of his work with foreign interests violated the Foreign Agents Registration Act, which requires disclosure of lobbying activities for other countries.
Mr. Biden pursued a variety of moneymaking ventures around the world for several years, some of them overlapping with his father’s time as vice president. They included serving on the board of a Ukrainian energy company, Burisma, and pursuing investment deals in China, bringing him millions of dollars in income.
Hunter Biden’s international business is at the heart of the efforts by House Republicans to find evidence that would justify impeaching President Biden. While Republicans have shown that President Biden, while vice president, had some passing interactions with business associates of his son, they have yet to produce any solid evidence that he took any actions to benefit Hunter or his associates or acted illegally or unethically.
The incident with the gun came after President Biden had left the vice presidency and before he announced his 2020 presidential candidacy.
Mr. Biden’s lawyers have argued to Justice Department officials that the charge will ultimately be thrown out because a series of Supreme Court and appeals court decisions have cast doubt on the constitutionality of the federal government putting certain conditions on firearms purchases.
Mr. Weiss, who is the U.S. attorney for Delaware and was appointed to that post by Mr. Trump, filed the gun charges in Delaware, where the handgun purchase took place. Should he file charges related to Mr. Biden’s taxes, his status as special counsel would allow him to do so in other jurisdictions where Mr. Biden was living during the period when he failed to file on time, including California and Washington, D.C.
The investigation of Mr. Biden appeared to have come to a conclusion this summer, when his lawyers and Mr. Weiss announced a plea deal and a hearing was scheduled at the federal courthouse in Delaware.
Mr. Biden was to plead guilty to two misdemeanor tax charges under that agreement. Regarding the gun purchase, prosecutors agreed not to prosecute him on the charge under a so-called pretrial diversion agreement, which would have required Mr. Biden to admit that he was using drugs at the time of the purchase.
The deal was contingent on Mr. Biden remaining drug free for the next two years. Mr. Biden has said he has been sober since 2019.
But at the plea hearing in federal court in July, the deal unraveled. There was a major disagreement between Mr. Weiss’s prosecutors and Mr. Biden’s lawyer, Christopher J. Clark, about whether the deal included an immunity clause that insulated him from being prosecuted in connection with his foreign business dealings.
Judge Maryellen Noreika of the Federal District Court in Wilmington sharply questioned elements of the deal’s structure, telling the two sides repeatedly that she had no intention of being “a rubber stamp.”
Her objections centered on two elements of the proposed deal. One was a provision that would have offered Mr. Biden broad insulation against further prosecution on matters scrutinized by federal prosecutors during the five-year inquiry. The other had to do with the diversion program on the gun charge, under which she would be called on to play a role in determining whether Mr. Biden was meeting the terms of the deal.
Judge Noreika said she was not trying to sink the agreement, but to strengthen it by ironing out ambiguities and inconsistencies. But by the end of the tumultuous hearing, the sides had splintered, prosecutors filed paperwork indicating they would proceed with a prosecution, and the embattled Mr. Weiss requested to be named special counsel, which requires him to file a report at the conclusion of the investigation.
The indictment unsealed on Thursday was not a surprise. On Sept. 6, Mr. Weiss told the court he planned to bring gun charges before the end of the month.
The Hunter Biden investigation has become a central focus of House Republicans and Mr. Trump, who has seized upon it as a counter to his own legal woes. Speaker Kevin McCarthy said on Tuesday that the House would proceed with a formal impeachment investigation.
The Justice Department has been investigating Hunter Biden since 2018. Despite looking into an array of matters — including his work for Burisma, his ties to oligarchs and the business deals in China — the investigation ultimately narrowed to the questions about Mr. Biden’s taxes and the gun purchase.
Those charges, while serious, were far less explosive than ones pushed by Mr. Trump and congressional Republicans, who have been angry with the Justice Department for failing to find wider criminal wrongdoing by the president’s son and family.
Mr. Biden has remained sober, and has been regularly checking in with a federal probation officer, according to two people familiar with his actions.