Alexander Smirnov, the former F.B.I. informant charged with falsely claiming that President Biden and his son Hunter had accepted bribes, will be held in custody indefinitely because he poses a significant flight risk, a judge in California ruled on Monday.
After a 45-minute hearing, a bespectacled Mr. Smirnov — stocky, bearded with close-cropped salt-and-pepper hair and wearing tan and orange prison togs — pleaded not guilty in heavily accented English, turning around briefly to wave at his longtime girlfriend seated in the gallery.
Judge Otis D. Wright II of Federal District Court found fault with a decision by a federal magistrate in Las Vegas who last week released Mr. Smirnov, 43, a confidential informant since 2010, and dismissed the argument by prosecutors that he would try to escape to Russia.
Prosecutors working for David C. Weiss, the special counsel investigating Hunter Biden, offered new details about the circumstances of Mr. Smirnov’s rearrest last week in the office of his lawyer. They grew alarmed after a search of the $980,000 condo owned by Mr. Smirnov’s girlfriend and where he has lived for the past two years revealed nine handguns, they said.
A prosecutor for Mr. Weiss, Leo Wise, explained that the sheer number of guns prompted Justice Department officials to make an arrest at the law office, rather than Mr. Smirnov’s home, which they believed would not be safe. They were able to track his movements because of an ankle monitor.
Mr. Smirnov’s lawyer, David Chesnoff, explained that Mr. Smirnov was at his office at the time of his rearrest because he was eager to begin preparing his defense. He said he planned to appeal the decision.
Asked outside the courthouse whether his team had in fact sought to help its client flee the country as prosecutors have suggested, Mr. Chesnoff appeared to sidestep the question.
“I think that’s a dead issue,” he said, adding, “I don’t think there’s any controversy.”
Judge Wright also expressed concern about Mr. Smirnov’s finances. Prosecutors had accused Mr. Smirnov, a dual U.S.-Israeli citizen, of intentionally underestimating his personal wealth of $6 million and found a recent flood of outflows from his accounts, hundreds of thousands of dollars a year, to be suspicious.
“There is nothing garden variety about this case,” Judge Wright said.
Mr. Chesnoff argued that his client was a loyal American who would not flee the country. He complained that Mr. Smirnov was being treated more harshly than the disgraced financier Bernie Madoff, who had been allowed to go free pending trial after he agreed to wear an ankle monitor.
Mr. Madoff “ripped off all of America and half of Europe,” he said.
Mr. Smirnov was escorted out of the courtroom and placed into protective custody, apart from the general population of the federal lockup in Los Angeles.
On Friday, Mr. Smirnov was transported to California by U.S. marshals in part because the case had been brought in federal court in the state.
Mr. Smirnov was arrested on Feb. 15 as he disembarked from an international flight in Las Vegas, where he has lived for the past two years with his girlfriend.
In 2020, Mr. Smirnov told his F.B.I. handler what prosecutors say was a brazen lie: that the oligarch owner of the Ukrainian energy company Burisma had arranged to pay $5 million in bribes to both Hunter Biden and his father. The explosive claim was leaked to Republicans, who made it public apparently without verifying it.
At the time of his arrest, Mr. Smirnov was planning to leave for what prosecutors called “a monthslong, multicountry foreign trip” during which he claimed to have plans to meet with contacts from multiple foreign intelligence agencies.
For more than a decade, Mr. Smirnov, who speaks English and Russian, gave the F.B.I. visibility into the shadowy world of oligarchs and public officials while offering himself as a consultant to some of the same people he was monitoring.
In court filings, the special counsel described Mr. Smirnov as a serial liar who could not even be trusted to honestly describe his occupation or account for his finances.