A Colorado man plans to plead guilty to killing a Montana teacher in a case that drew attention to the darker side of the Northern Plains' oil boom.

A plea agreement with prosecutors filed Tuesday calls for a 100-year sentence for 25-year-old Michael Spell on a charge of deliberate homicide.

Spell is charged with the 2012 murder of Sherry Arnold, a 43-year-old Sidney high school teacher who disappeared while jogging. Her body was found buried in a North Dakota field.

Spell is due in court Wednesday before District Judge Richard Simonton in Sidney.

Prosecutors want Spell to serve his time in prison. The defense will ask for him to be sentenced to the state health department, which would allow Spell to be sent to a facility for the mentally disabled.