• John Pierce — a lawyer representing 17 criminal defendants in Jan. 6 Capitol riot cases — has gone missing from court appearances amid excuses that include a claim he is hospitalized with Covid-19.
• Pierce's clients include members of far-right Proud Boys and Oath Keepers groups.
• Prosecutors warned a judge that Pierce associate Ryan Marshall — who has been appearing in Pierce's absence over the past week — "is not a licensed attorney."
• Hundreds of people are charged with being part of a mob of supporters of then-President Trump who besieged the Capitol complex to oppose the confirmation of Joe Biden as president.

Lawyer John Pierce — who is representing 17 criminal defendants in Capitol riot cases — has gone missing from court appearances amid conflicting excuses that include a claim he is hospitalized with Covid and is on a ventilator, a court filing says.

Federal prosecutors warned a judge in the filing that Pierce associate Ryan Marshall — who has been appearing in Pierce's absence over the past week — "is not a licensed attorney." Marshall also faces two separate felony criminal cases pending against him in Pennsylvania, the prosecutors said.

As a result, "Mr. Marshall cannot ethically or legally represent Mr. Pierce's clients," prosecutors from the U.S. Attorney's Office for the District of Columbia told the judge in Monday's filing, which was made in the case of riot defendant James Burton McGrew.

"The United States thus finds itself in a position where this defendant and 16 other defendants charged in connection with the Capitol Riot appear to be effectively without counsel," prosecutors wrote Chief Judge Beryl Howell of Washington federal court.

All of Pierce's riot defendants are being prosecuted in that court, as are hundreds of others accused of invading the Capitol complex on Jan. 6 after then-President Donald Trump urged supporters to fight against the confirmation of Joe Biden's election as president by a joint session of Congress.

Pierce's clients include members of the far-right Proud Boys and Oath Keepers groups.

Monday's filing appears to give the benefit of the doubt to an initial claim by Marshall that Pierce, who is a Trump supporter himself, is, "Sadly ... ill with COVID-19, on a ventilator, and unresponsive."

"Unfortunately, it seems that Mr. Pierce may be hospitalized and unable to communicate, and it is unclear when Mr. Pierce will recover," prosecutors wrote.

"The government is making the Court aware of Mr. Pierce's reported illness so that it can take any steps it believes necessary to ensure the defendant's rights are adequately protected while Mr. Pierce remains hospitalized," the filing said.

Prosecutors also mention other reports that contradict that claim and give other explanations for the mysterious absence of Pierce, a name partner in the Los Angeles law firm Pierce Bainbridge.

"I have nothing to say," Marshall told CNBC on Tuesday.

When CNBC called the main office phone number of Pierce's firm on Tuesday, a recording said, "The number you called is not in service."

Pierce did not answer a phone number given for him on the court's docket. A message on that phone number said its voice mail had not been set up. Pierce did not immediately respond to an email query.

CNBC has left a message seeking comment with his firm on its online contact form.

Pierce previously represented Kyle Rittenhouse, an 18-year-old Illinois man charged with reckless homicide and other charges for fatally shooting two people and wounding a third in Kenosha, Wisconsin, last August during a civil disturbance sparked by the non-fatal police shooting of Black man named Jacob Blake.

Rittenhouse fired Pierce in February.

An article in The New Yorker in June detailed the events leading up to Pierce's termination, which included how the lawyer handled donations earmarked for Rittenhouse.

"Kyle was John's ticket out of debt," Rittenhouse's mother, Wendy Rittenhouse, told The New Yorker.

In their filing Monday, federal prosecutors wrote that they have "had no contact with Mr. Pierce — by phone, e-mail, or otherwise — since Monday, August 23, 2021," when he appeared in D.C. court for a hearing in the case of Capitol riot defendant Jeremiah Caplinger.

"Since that time, the U.S. Attorney's Office has heard conflicting information about Mr. Pierce's health and whereabouts," the filing.

On Aug. 24, Marshall appeared in court Pierce's place for another riot defendant, "and represented to the court that Mr. Pierce's absence was due to a conflict," the filing said.

"A few hours later, Mr. Marshall attended a reverse-proffer session with a different defendant represented by Mr. Pierce, telling the Assistant U.S. Attorney that he had just gotten word that Mr. Pierce had been in an accident and was on his way to the hospital," the filing said.

"Mr. Marshall then proceeded with the reverse-proffer session in Mr. Pierce's absence."

The next morning, Marshall appeared in Pierce's place for yet another riot defendant, "and represented to the court that Mr. Pierce was hospitalized with COVID-19, on a ventilator, and non-responsive," the filing said.

"After that information was reported publicly, a different individual reached out to an NPR correspondent and wrote that Mr. Pierce did not, in fact, have COVID, but instead 'was hospitalized on Monday due to symptoms that he believed might be related to Covid-19'; 'appears to have been suffering from dehydration and exhaustion'; and 'remains under the care of his doctors,' " the filing said.

Last Thursday, during a hearing for another defendant, Marshall told a judge that he had not had direct contact with Pierce, "but that one of Mr. Pierce's friends had told him that Mr. Pierce was sick with COVID-19 and another had said he was not," prosecutors wrote.

The filing noted that during the hearing, "Marshall requested, and was granted, a sealed bench conference at which to discuss Mr. Pierce's condition."

Prosecutors noted that Pierce routinely posted "multiple messages to Twitter on a daily basis" but has not done so since Aug. 20.

"And there are reports that "multiple phone numbers for Pierce's law firm, Pierce Bainbridge P.C., have been disconnected," the filing said.

Prosecutors said that Marshall seems to have taken actions for Capitol riot defendants "that he is not permitted to do," as he is not being currently licensed to practice law, "and thus cannot appear in this Court, represent Mr. Pierce's clients, or provide them with legal advice or services."

The filing noted that Marshall is criminally charged in Pennsylvania state court with multiple counts of intercepting communications and unlawful use of an audio device in court, and in another case there where he is accused of a scheme to defraud the widow of a man while serving as a courthouse law clerk.

"From the government's perspective, given Mr. Pierce's reported illness and the fact that Mr. Marshall is not a licensed attorney, this case is effectively at a standstill," the filing said.

Prosecutors wrote that while '"Marshall has been the government's main or sole point of contact for many of the defendants represented by Mr. Pierce, the government does not believe it appropriate to continue to communicate with him in Mr. Pierce's absence, during which he would necessarily be acting without supervision by a licensed attorney."

Correction: An earlier version gave the wrong last name for Judge Beryl Howell.