Homicide

Colorado man plans to plead guilty in Montana teacher killing that rattled Bakken oil patch

  • FILE - This undated file photo provided by the Williams County, N.D., Sheriff's Department shows Michael Keith Spell. A plea agreement with prosecutors filed Tuesday, Oct. 21, 2014, calls for a 100-year sentence for Spell, 25, on a charge of deliberate homicide for the 2012 death of Sherry Arnold. A charge of attempted kidnapping would be dropped. (AP Photo/Williams County, N.D., Sheriff's Department, File)

    FILE - This undated file photo provided by the Williams County, N.D., Sheriff's Department shows Michael Keith Spell. A plea agreement with prosecutors filed Tuesday, Oct. 21, 2014, calls for a 100-year sentence for Spell, 25, on a charge of deliberate homicide for the 2012 death of Sherry Arnold. A charge of attempted kidnapping would be dropped. (AP Photo/Williams County, N.D., Sheriff's Department, File)  (The Associated Press)

  • FILE - This undated photo provided by the Sidney, Mont., Police Dept. shows missing Sidney High School math teacher Sherry Arnold. A plea agreement with prosecutors filed Tuesday, Oct. 21, 2014, calls for a 100-year sentence for Michael Keith Spell, 25, on a charge of deliberate homicide for the 2012 death of Arnold. A charge of attempted kidnapping would be dropped.  (AP Photo/Sidney Montana Police Dept., File)

    FILE - This undated photo provided by the Sidney, Mont., Police Dept. shows missing Sidney High School math teacher Sherry Arnold. A plea agreement with prosecutors filed Tuesday, Oct. 21, 2014, calls for a 100-year sentence for Michael Keith Spell, 25, on a charge of deliberate homicide for the 2012 death of Arnold. A charge of attempted kidnapping would be dropped. (AP Photo/Sidney Montana Police Dept., File)  (The Associated Press)

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.