Alexander Smirnov, 43, the former F.B.I. informant accused of peddling lies about President Biden and his son Hunter, is scheduled to appear in federal court on Friday after being arrested for the second time in a week.
Mr. Smirnov was sitting in his lawyer’s office in Las Vegas Thursday morning when U.S. Marshals burst in to take him into custody.
The hearing will determine if prosecutors had the right to rearrest him two days after a magistrate judge freed him — a highly unusual and aggressive move the government claims was needed to safeguard national security and prevent him from fleeing overseas.
The bizarre episode is the latest development in a case that has spawned public interest and confusion in equal measure, centering on an enigmatic fixer whose accusations formed the fractured bedrock of a push by Republicans to impeach Mr. Biden.
The hearing, before Judge Daniel Albregts in Nevada, is expected to be highly contentious but unlikely to alter the trajectory of the case. Prosecutors indicted Mr. Smirnov last week in California, where the special counsel David C. Weiss has brought tax charges against Hunter Biden. The judge in that jurisdiction authorized Mr. Smirnov’s rearrest on Thursday.
Mr. Weiss’s actions not only pit him against the defense team but also against the magistrate who released Mr. Smirnov on his own recognizance, without cash bond, after requiring him to turn over his passports and wear an electronic monitoring device.
When Leo Wise, who represented the special counsel at the first detention hearing on Tuesday, suggested that Mr. Smirnov might flee the country and seek refuge in Russia, the judge sided with the defense, breezily dismissing that argument.
“My guess is at this stage he probably thinks that’s not the most attractive place to go if he was in fact inclined to go hide somewhere,” the judge said, according to the court transcript.
In a filing on Thursday, Mr. Smirnov’s lawyer, David Z. Chesnoff, accused Mr. Weiss of blindsiding his client with “an arrest warrant for Mr. Smirnov based on the same charges.”
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 in a $980,000 apartment with his longtime 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 the president and Hunter Biden. 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 describe honestly his occupation or account for his finances.
Mr. Chesnoff disputed those characterizations in court this week and suggested he would seek to introduce into evidence that Mr. Smirnov was a truthful and patriotic source of important intelligence for the F.B.I.
“There will be a vehement defense to the argument that in fact he was not truthful,” Mr. Chesnoff said.