Lawyers for convicted sniper John Allen Muhammad (search) asked a judge to throw out charges against him, saying prosecuting him again violates his right against being tried twice for the same offense.

The request was among motions filed in the case Thursday in Fairfax County, where Muhammad faces trial for the Oct. 14, 2002, killing of Linda Franklin (search), an FBI analyst.

Muhammad, 43, was convicted last fall and sentenced to death for one of the nine other fatal shootings in the Washington, D.C., area in October 2002.

Prosecutors say they want to ensure that Muhammad gets the death penalty by convicting him on a capital charge in a second sniper slaying in case the first conviction is overturned on appeal.

Fairfax Commonwealth's Attorney Robert F. Horan Jr. did not return a message seeking comment. He must respond to the defense motions by the end of next week.

Muhammad and co-conspirator Lee Boyd Malvo (search), 19, were tried separately for the sniper shootings. Both were convicted of murder as an act of terrorism and committing more than one murder in a three-year period.

Muhammad was sentenced to death and Malvo was sentenced to life in prison without parole.