A Colorado man faces sentencing Monday in the killing of a Montana math teacher in a case that has emerged as a chilling example of the social changes accompanying an oil boom sweeping the Northern Plains.

Lester Van Waters Jr., 50, of Parachute, Colorado, pleaded guilty last year to a count of deliberate homicide by accountability. The case is before Montana District Judge Richard Simonton.

Prosecutors say Waters and accomplice Michael Spell killed 43-year-old Sidney High School teacher Sherry Arnold during an attempted abduction.

Arnold, a mother of two and popular teacher in the close-knit city of Sidney, was killed just blocks from her house after going out for a morning jog on Jan. 7, 2012. Her body was found more than two months later buried in a rural area of North Dakota.

Spell and Waters traveled to Sidney from Colorado, using crack cocaine throughout their journey, according to authorities and previous testimony from the men. They had told friends and family they were searching for work in the Bakken oil fields along the Montana-North Dakota border, where an oil boom has boosted agricultural communities but brought a spike in crime.

Waters allegedly told Spell that using crack "brought the devil out in him" and began talking about kidnapping and killing a female, according to an affidavit filed by prosecutors.

Authorities said Arnold was choked or otherwise asphyxiated after Spell tried to grab her. Spell said during a change-of-plea hearing in October that he was unsure if he or Waters had killed Arnold.

Waters made a deal with prosecutors that called for him to testify against Spell if the case went to trial. In exchange, Waters would be spared the death penalty and prosecutors would recommend he receive 100 years in prison, with 20 years suspended.

Waters had a lengthy criminal background in Florida, where he lived until after his most recent release from prison in August 2010.

Beginning in the late 1980s, he had several stints in jail in Florida's Indian River County and served three state prison sentences between 2002 and 2010.

Spell has pleaded guilty to deliberate homicide. His sentencing has not been scheduled.