BOZEMAN, Mont. -

Defense attorneys are seeking to avoid the death penalty for one of two men charged in the killing of a Montana high school teacher because they say the suspect is mentally disabled.

Twenty-four-year-old Michael Spell of Colorado faces charges including deliberate homicide for the alleged January 2012 kidnapping and murder of Sidney teacher Sherry Arnold.

Defense attorney Al Avignone said Tuesday he's asked the court to rule Spell ineligible for execution under a 2002 U.S. Supreme Court ruling that outlawed capital punishment for the mentally disabled.

Prosecutors have until Aug. 21 to respond to the motion.

Avignone also is seeking to have Spell's 2014 trial moved to Bozeman. He says widespread news coverage of Arnold's killing in the booming Bakken oil patch of Montana and North Dakota has biased potential jurors.