A Colorado man is scheduled to be sentenced Friday for the murder of a Montana teacher whose death highlighted the downsides of an oil boom that has brought thousands of newcomers to the remote Northern Plains.

Prosecutors have recommended 100 years in prison for 25-year-old Michael Keith Spell of Parachute, Colorado, for the 2012 killing of Sherry Arnold.

Defense attorneys want Spell sentenced to an institution for the mentally disabled. They say co-defendant Lester Van Waters threatened to kill Spell unless he went along with Waters' plan to kidnap a woman.

The body of Arnold, a popular 43-year-old math teacher at Sidney High School, was found in a shallow grave near Williston, North Dakota, months after her disappearance.

Spell and Waters had come to the region to work in the Bakken oil patch.