The judge presiding over the case of sniper John Allen Muhammad removed himself from the trial yesterday because he conducted his own investigation into facts under dispute in pretrial proceedings, a move that prosecutors argued was a violation of judicial conduct.Fairfax County Circuit Court Judge Jonathan C. Thacher recused himself from the trial “sua sponte,” which is Latin for “of one’s own accord,” rather than in response to prosecutors’ recent motion for recusal. In a letter to prosecutors and defense lawyers made public yesterday, the judge thinks he did nothing wrong.”My concerns and obligations are and always have been the orderly administration of justice” and following the law, Judge Thacher wrote. “As the trial judge, I have taken no action that is inconsistent with this position.”But the judge said he needed to step aside because “the focus has been diverted away from the legal issues in this case and needs to be redirected to the prosecution of Mr. Muhammad.”“The integrity of the process is paramount,” Judge Thacher wrote. “Anything that detracts from the orderly disposition of this case must therefore be secondary and yield.”Circuit Court Judge M. Langhorne Keith will replace Judge Thacher. A pretrial hearing in the case is scheduled for this morning.Fairfax County Commonwealth’s Attorney Robert F. Horan Jr. filed a motion on Sept. 8 asking the judge to recuse himself from the trial, after learning that he had gone to the Prince William County jail — where Muhammad was held during his first capital murder trial — to get documents and talk with witnesses about a motion filed by Muhammad’s attorneys.Mr. Horan’s office also filed a motion on Friday, saying that the court had “abandoned its role as a neutral arbiter of the facts.”“I think he did what he had to do,” Mr. Horan said yesterday, referring to Judge Thacher’s recusal.Defense attorneys Peter D. Greenspun and Jonathan Shapiro filed a motion on Aug. 17 to dismiss the case against Muhammad in Fairfax County, arguing that the county had violated their client’s right to a speedy trial. Virginia law requires that a defendant be tried within five months of an indictment.Muhammad’s attorneys argued that a Nov. 6, 2002, grand jury indictment in Fairfax, should have resulted in a trial within five months of that date. Prosecutors argued that the Fairfax indictment was a detainer and cited Virginia code, which indicates that the speedy trial requirements do not kick in until the defendant is arrested. Mr. Greenspun and Mr. Shapiro declined to comment on the case yesterday, except to say that “it is important to state affirmatively our utmost respect for Judge Thacher, his integrity and the work he put into assuring a fair trial for John Muhammad and the commonwealth.”Fairfax authorities arrested Muhammad, 43, in May while on death row. Muhammad was sentenced to death in Prince William County Circuit Court for the Oct. 9, 2002 fatal shooting of Dean H. Meyers, 53, at a Manassas gas station. Mr. Meyers was a victim of one of 13 sniper shootings in the Washington area during three weeks in October 2002. That case is under automatic appeal.Muhammad is scheduled to go on trial in Fairfax County on Jan. 10 for the Oct. 14, 2002, fatal shooting of FBI analyst Linda Franklin, 47, outside a Falls Church Home Depot.Muhammad and his accomplice Lee Boyd Malvo, 19, have been linked to 22 shootings, 15 of them fatal, across the country. Malvo was sentenced to life in prison last year for Mrs. Franklin’s slaying and will be tried again, most likely in Prince William County, if the U.S. Supreme Court next spring upholds the death penalty for juvenile criminals. Malvo was 17 at the time of the shootings.Attorney Joseph Bowman, who has defended several capital murder cases in Northern Virginia, called Judge Thacher’s actions a “really, really unusual thing to do, and it indicates to me that he doesn’t trust the prosecutor’s office.”Judge Keith, 67, has been on the bench in Fairfax County since March 1995. He presided over Malvo’s pretrial hearings in Fairfax before Circuit Judge Jane Marum Roush was assigned the case. Judge Keith is a former president of the Virginia Bar Association and was a partner in the Virginia office of Hogan & Hartson prior to being elected a judge. He grew up in Fairfax County, graduated from the University of Virginia Law School in 1970 after serving nine years in the U.S. Navy.His last high-profile case was that of Seema Rothstein, a fourth-grade teacher who fatally stabbed her 36-year old husband in November 2001. Rothstein, 32, was found guilty of involuntary manslaughter when prosecutors and defense attorneys agreed that she suffered from postpartum psychosis at the time of the killing. Judge Keith gave her a suspended five-year sentence, placed her on five years’ probation and ordered that she receive mental-health treatment.