Federal prosecutors disclosed Wednesday that a witness expected to testify for the defense at the seditious conspiracy trial of former Proud Boys leader Enrique Tarrio and four associates was secretly acting as a government informant for nearly two years after the Jan. 6, 2021, attack on the U.S. Capitol, a defense lawyer said in a court filing.

Carmen Hernandez, a lawyer for former Proud Boys chapter leader Zachary Rehl, asked a judge to schedule an immediate emergency hearing and suspend the trial "until these issues have been considered and resolved." Lawyers for the other four defendants joined in Hernandez's request.

Hernandez said in court papers that the defense team was told by prosecutors on Wednesday afternoon that the witness they were planning to call to the stand on Thursday had been a government informant.

The judge ordered prosecutors to file a response to the defense filing by Thursday afternoon and scheduled a hearing for the same day, putting testimony in the case on hold until Friday. The U.S. attorney's office did not immediately comment on the filing.

In her court filing, Hernandez said the unnamed informant participated in "prayer meetings" with relatives of at least one of the Proud Boys on trial and had discussions with family members about replacing one of the defense lawyers on the case. The informant also has been in contact with at least one of the defense lawyers and at least one of the five defendants, Hernandez wrote.

It's the latest twist in a trial that has been bogged down by bickering between lawyers and the judge and already lasted much longer than expected. Defense lawyers have repeatedly asked the judge in vain to declare a mistrial over a variety of issues they say have been unfair to their clients.

The trial in Washington's federal court is one of the most serious cases to emerge from the Jan. 6 attack. Tarrio, Rehl and three other Proud Boys — Joseph Biggs, Ethan Nordean and Dominic Pezzola — are charged with conspiring to block the transfer of presidential power from Donald Trump to Joe Biden after the 2020 election.

Tarrio, a Miami resident, served as national chairman for the far-right extremist group, whose members describe it as a politically incorrect men's club for "Western chauvinists." He and the other Proud Boys could face up to 20 years in prison if convicted of seditious conspiracy.

Defense attorneys have argued there is no evidence the Proud Boys plotted to attack the Capitol and stop Congress from certifying Biden's electoral victory.

Hernandez didn't name the informant in her court filing, but she said it is somebody who has serving as a "confidential human source" for the federal government since April 2021 through at least January 2023. Prosecutors knew in December that the person was a potential trial witness but didn't inform defense lawyers until Wednesday that the witness has been a federal informant, she said.

It's not the first time the government's use of informants has become an issue in the case. Defense attorneys have repeatedly pushed to get more information about informants in the far-right extremist group as they try to undermine the notion that the group had a plan to attack the Capital on Jan. 6.

FBI Agent Nicole Miller testified last week that she was aware of two informants in the Proud Boys, including one who marched on the Capital on Jan. 6.

Hernandez said there are "reasons to doubt the veracity of the government's explanation and justification for withholding information about the (confidential human sources) who have been involved in the case." She could not immediately be reached for additional comment.

Law enforcement routinely uses informants in criminal investigations, but their methods and identities can be closely guarded secrets. Federal authorities haven't publicly released much information about their use of informants in investigating the Proud Boys' role in a mob's attack on the Capitol on Jan. 6.

Nordean, of Auburn, Washington, was a Proud Boys chapter leader. Biggs, of Ormond Beach, Florida, was a self-described Proud Boys organizer. Rehl was president of the Proud Boys chapter in Philadelphia. Pezzola was a Proud Boys member from Rochester, New York.

- MICHAEL KUNZELMAN and LINDSAY WHITEHURST Associated Press