BILLINGS, Mont. -

Prosecutors say they no longer will pursue the death penalty against a Colorado man suspected of killing a teacher in eastern Montana's oil patch.
    
Tuesday's move by Richland County Attorney Mike Weber comes after psychiatrists determined 25-year-old Michael Keith Spell is mentally disabled.
    
Spell is charged with killing 43-year-old Sherry Arnold, who disappeared while jogging along a Sidney street in 2012.
    
Weber cited a 2002 U.S. Supreme Court ruling that said executing mentally disabled criminals constitutes cruel and unusual punishment.
    
A state judge on Friday rejected attempts by Spell's attorneys to have him declared incompetent. That would have let him avoid trial.
    
Spell now faces a maximum of life in prison if convicted on charges of attempted kidnapping and deliberate homicide.
    
An accomplice pleaded guilty in a deal with prosecutors.