BILLINGS (AP) — The Montana Supreme Court rejected a Colorado man’s petition to be declared unfit to stand trial in the murder of a high school teacher in the Bakken oil patch, as the case approaches a Nov. 17 trial.

Both sides in the case agree that Michal Keith Spell is mentally disabled. He has a history of low scores on intelligence tests dating to his childhood and exhibits difficulty reading.

But prosecutors and a lower court judge overseeing the case rejected arguments that Spell’s mental condition rendered him unable to understand the case against him or participate in his defense.

The state high court agreed in a unanimous ruling issued Tuesday. The court said state law does not “automatically” preclude a mentally disabled suspect from being tried.

“The United States Supreme Court has observed that intellectually disabled persons frequently know the difference between right and wrong and are competent to stand trial,” justices wrote.

Spell, 25, of Parachute, Colorado, faces a Nov. 17 trial in the death of Sherry Arnold. The 43-year-old Sidney High School math teacher disappeared while on a morning jog near her house in January 2012. Her body was found more than two months later in a shallow grave in nearby North Dakota, at the center of the Bakken oil boom.

Justices said that state District Judge Richard Simonton acted within his discretion when he ruled in May that Spell’s competency had been restored since a 2010 drug case in Colorado in which he was declared incompetent.

Simonton made a “fact-driven determination,” justices wrote, adding that it would be inappropriate for them to intervene at this stage in the case.

Defense attorney Al Avignone said he was disappointed in the high court’s ruling.

“We were hoping the court would address the merits of the more substantial arguments that we made. They simply said those arguments involve factual issues more appropriately determined on a direct appeal,” Avignone said.

Richland County Attorney Mike Weber, who is leading the prosecution, did not immediately respond to a request for comment.

Spell is charged with attempted kidnapping and deliberate homicide. He faces a maximum of life in prison.

Prosecutors initially sought the death penalty in the case. They dropped that pursuit after a psychiatrist from the state mental hospital in Warm Springs agreed with defense experts that Spell is mildly mentally disabled.

In 2002, a U.S. Supreme Court ruling outlawed the execution of defendants who have a mental or intellectual disability.

An accomplice, Lester Van Waters, pleaded guilty last year under a deal with prosecutors that allowed him to avoid the death penalty. He has yet to be sentenced.