SIDNEY, Mont. -

A Colorado man's bid to avoid trial and a potential death sentence in the killing of a Montana teacher on Monday goes before a state judge, who will to decide if the defendant is incompetent due to mental disability.

His attorneys say 24-year-old Michael Keith Spell has the mental capacity of a first-grader and is unfit for trial. If Judge Richard Simonton agrees, Spell could be sent to a state institution and could be eligible for eventual release.

He's charged with murder in the death of Sherry Arnold in January 2012. The teacher disappeared as she was jogging near her home in Sidney and her body was buried in North Dakota. An accomplice pleaded guilty under a plea deal that calls for him to testify against Spell.