Circuit Court Judge Thomas Russo ruled Tuesday afternoon the state can not seek the death penalty against David Johnson, 25.
State mental health experts found Johnson was intellectually disabled, and the law says you can't seek the death penalty in that case.
Solicitor Ed Clements says he can't go into the specifics of the experts' findings, because it would violate federal health privacy laws.
Her relatives reported her missing and her body was later found in a ditch.
Clements says now they're waiting to learn if Johnson is competent to stand trial, even though he's been declared intellectually disabled.
He says there are specific standards that medical experts look for to determine if he's competent.
"He's got to have the ability to differentiate between right and wrong and to conform his actions to that at the time of the offense, " said Solicitor Ed Clements.
Clements says he thinks Johnson will be found competent because he has held down a job in the past and because of his role in the murder.
Johnson's competency hearing is set for January 24th.
If he's found competent to stand trial, he will be tried on February 13th.
The three other suspects have yet to be tried.