Gary Dunn, 30, is charged with capital murder in the Dec. 15, 2005, death of 19-year-old Nona Dirksmeyer in Dirksmeyer's apartment in Russellville. Prosecutors have said they will seek the death penalty.
Dunn's attorneys say prosecutors apparently want Dunn's wife to testify about their marital sexual relationship. Their motion says such a relationship is clearly private.
Prosecutors have not yet responded to the motion.
Dunn is the second man charged with Dirksmeyer's death. Dirksmeyer's boyfriend, Kevin Jones, was found not guilty in 2007 of first-degree murder in her death.
Dunn's trial is to start Sept. 28 in Clarksville.
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