A Colorado man has been sentenced to 100 years in prison in the murder of a Montana teacher whose death highlighted the downside of an oil boom that's altered the remote Northern Plains.

Twenty-five-year-old Michael Keith Spell was sentenced Friday by state District Judge Richard Simonton in Sidney, Montana.

Spell pleaded guilty in October to killing 43-year-old Sherry Arnold after attempting to abduct the popular math teacher as she was jogging near her home in 2012. Arnold's body was found months later in near Williston, North Dakota.

Defense attorneys wanted Spell sentenced to an institution for the mentally disabled.

Co-defendant Lester Van Waters Jr. received 80 years in prison in December.

The two men came to the region looking for work in the Bakken oil patch.