The Fairfax County judge overseeing sniper John Allen Muhammad's case questioned Prince William County jailers about their powers and procedures, altered Muhammad's jail file and repeatedly suggested that a key document had been doctored, Fairfax prosecutors contended in a renewed motion that the judge step down.

On Friday, the prosecutors filed a brief with eight pages of detailed allegations about Fairfax Circuit Court Judge Jonathan C. Thacher's actions in Prince William and argued that if Thacher does not recuse himself, the decision "may be grounds for reversal of a conviction where the trial judge has abused his discretion."

Thacher has become the center of attention in Muhammad's second trial in the October 2002 Washington area sniper shootings. Defense attorneys last month argued that the Fairfax charges should be dismissed because Muhammad's right to a speedy trial had been violated. Prosecutors responded that the clock did not begin ticking until Muhammad was arrested on the Fairfax charges in May of this year.

When the defense countered that Muhammad actually had been arrested by Fairfax in the Prince William County Regional Adult Detention Center in January, the prosecutors put in a request Sept. 3 for an evidentiary hearing. Four days later, Thacher traveled to the Prince William courthouse in Manassas to review Muhammad's jail file and speak with his jailers.

Fairfax prosecutors learned of Thacher's unorthodox research journey almost immediately and the next day filed a motion asking Thacher to recuse himself, saying he had violated judicial canons by launching his own investigation of a defense motion and interviewing potential witnesses.

Thacher, who has been screening all filings in the case, did not release that brief to the public Friday. The same day, Muhammad's defense attorneys filed a brief defending the judge's actions and saying he should not step down. That brief was released the day it was filed; the prosecution's brief was posted yesterday.

In it, Deputy Commonwealth's Attorney Raymond F. Morrogh said that if Thacher declined to recuse himself based solely on the legal briefs, he should hold an evidentiary hearing on the issue before he rules on any other matters.

Thacher did not return a call seeking comment yesterday and has previously declined to discuss the case. Fairfax Commonwealth's Attorney Robert F. Horan Jr. did not return a call seeking comment.

Prosecutors said Thacher specifically inquired about issues that would have been raised before him at a hearing, which is now scheduled for Wednesday. After Muhammad's attorneys produced documents showing that Muhammad apparently was served with Fairfax arrest papers, prosecutors replied that the Prince William jailers do not have arrest powers.

Thacher "asked jail officials about the scope of their arrest powers," Morrogh wrote, and also inquired "about their procedures regarding documents used to notify defendants of 'detainers.' "

A detainer is a notice from one county to another asking the county holding a prisoner to detain the prisoner on the first county's charges. In an Aug. 30 hearing, Thacher twice asked Horan for a copy of Fairfax's detainer. Days later, Muhammad's attorneys produced copies of a fax received by the Prince William jail from Fairfax police in January, asking that Muhammad be detained, as well as copies of Muhammad's Fairfax arrest warrant and a document indicating that it was served on Muhammad.

Virginia's speedy trial law requires that a jailed defendant be tried within five months. Muhammad's attorneys believe that the clock began ticking when Muhammad was first brought to Virginia in November 2002. And when prosecutors claimed that Muhammad was not arrested on the Fairfax charges until May of this year, the defense responded with the Prince William documents showing a January arrest.

In a meeting Sept. 7 with jail officials, Thacher reviewed Muhammad's jail file, according to the prosecution motion. Prosecutors said Thacher asked for a copy of a teletype sent by Fairfax police to the jail that requested Muhammad's detention. A copy of the teletype had been denied to Muhammad's attorneys as a matter of law. Prosecutors allege that the jailers initially refused the judge's request but that when he threatened to subpoena the teletype, they gave it to him.

Muhammad's jailers had placed Post-it notes on his file to mark the documents that had been provided to Peter D. Greenspun, one of Muhammad's attorneys. Morrogh wrote that Thacher removed all of the markers and did not replace them. The judge "altered the file," Morrogh wrote, and deprived prosecutors of an opportunity to show that Greenspun had not submitted all the relevant documents with his filings.

Thacher then viewed a faxed copy of Muhammad's bench warrant from Fairfax. Morrogh wrote that Thacher told the jailers "that the document had been altered" and pointed out how. The judge "further indicated that an Internal Affairs investigation by jail officials might now be warranted," Morrogh wrote. He noted that the jailers at the meeting have since hired lawyers and now refuse to speak with Fairfax investigators.

The judge reportedly asked the jailers whether the fax machine's memory still held the Muhammad warrant, according to the prosecutors. A jailer said he would check and called Thacher later that day in Fairfax.

"The jail official told the Trial Judge what he believed to be the explanation for the alteration to the document," Morrogh wrote. Thacher "expressed skepticism at the explanation," Morrogh said, "and made it clear that he suspected wrongdoing."

Morrogh said jail officials at the meeting said Thacher "speculated openly with regard to possible forthcoming defense motions in connection with the document."

The prosecution motion said it is the defense's burden to present documents in support of its motion to dismiss the case. "The very last thing that the Court should have done," Morrogh wrote, "was to go out and conduct an independent investigation on behalf of the defendant. When the Court did so it abandoned its role as a neutral arbiter of facts and law in this case."

Morrogh wrote that if the judge did not step down, "the integrity of these proceedings and ultimate outcome of this case will be in jeopardy."

Judge Jonathan Thacher of Fairfax went to Manassas to see documents.