BILLINGS, Mont. (AP) — A Montana judge will decide if a suspect’s alleged confession to his involvement in the slaying of a woman jogging through her town in the Bakken oil patch should be suppressed because the defendant is mentally disabled.

District Judge Richard Simonton on Thursday scheduled an Oct. 1 hearing in Glendive in the case of 25-year-old defendant Michael Keith Spell of Parachute, Colorado.

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Spell is accused of killing 43-year-old Sherry Arnold during an attempted abduction. The high school teacher and mother of two disappeared while jogging in Sidney in January 2012. Her body was found more than two months later in North Dakota.

Sherry Arnold (credit: Facebook)

Sherry Arnold (credit: Facebook)

Lester Van Waters Jr., also of Parachute, has pleaded guilty to deliberate homicide by accountability in a deal with prosecutors.

Richland County prosecutors dropped their pursuit of the death penalty for Spell after experts testified he is mildly mental disabled.

Spell allegedly confessed to his involvement in the crime six days after Arnold disappeared, during an interrogation by FBI agents in the hours following his arrest by a SWAT team in South Dakota.

The defense says Spell was not mentally capable of waiving his rights to remain silent and have an attorney present for the FBI interview. Spell’s attorneys want his statements — and any evidence obtained as a result — barred from his Nov. 17 trial.

“Mr. Spell is young (22 years old at the time of the interrogation), intellectually disabled, and based on his two most recent IQ scores, he has the mental age of about 11,” defense attorneys Al Avignone and Lisa Banick wrote. “Mr. Spell believed the FBI agents were his friends, and he was simply helping them solve the disappearance and murder of Mrs. Arnold.”

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The defense has not disputed that Spell was involved but contends there’s no definitive proof he killed Arnold.

Spell told the agents he and Waters had arrived in Sidney looking for work in the Bakken oil fields along the Montana-North Dakota border, according to excerpts of Spell’s interrogation cited by prosecutors. After smoking large amounts of crack cocaine, Waters said he wanted to kidnap and kill a woman.

After the first woman they hoped to target, at a public laundry, left before they could carry out their plan, Spell said the pair saw Arnold. Spell said he grabbed her and dragged her back to their vehicle, where Waters killed her, according to court documents.

Waters has implicated Spell as the killer.

Prosecutors have said there is no reason to throw out Spell’s statements because they were lawfully obtained. They said the FBI agents repeatedly sought to make sure Spell knew what was going on during his interrogation.

“Intellectual disability, while relevant, must be assessed in the totality of the circumstances,” Deputy County Attorney T.R. Halvorson wrote. “Otherwise, we would be punishing the police simply because of the defendant’s condition even though they have done nothing wrong.”

An expert for the defense, University of Washington clinical psychologist Craig Beaver, is expected to testify at the Oct. 1 hearing.

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By Matthew Brown, AP Writer (© Copyright 2014 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)