SIDNEY, Mont. -

The killing of a high school teacher has weighed heavily in rural Montana. Hundreds of people helped search for Sherry Arnold, and calls for frontier-style justice greeted the arrest of the man accused in her death.
    
Today, the fate of 24-year-old Michael Keith Spell rests not with a jury but with experts evaluating whether he should be declared unfit for trial. His attorneys say he has intellectual disabilities dating to his elementary school days in Colorado.
    
If he goes to trial, they say the death sentence sought by prosecutors should be barred under a U.S. Supreme Court ruling that forbids executions of the mentally disabled. Prosecutors are sending their own team to evaluate Spell.
    
A co-defendant has entered into a plea deal that calls on him to testify against Spell.