DURANT - A man charged with murder and scheduled for trial to determine if he was mentally retarded, and therefore eligible for the death penalty, entered a plea in the case.

Gary Wayne Olsen Jr. 23, pleaded guilty to accessory after the fact to first-degree murder, and was sentenced to 45 years in prison. Olsen originally was charged with first-degree murder for the death of Scotty Dean Sheffield, 23, who was slain in September 2005.

Investigators said Sheffield was beaten and shot. After receiving a tip, authorities found the body in a shallow grave off Old Highway 70 near the Blue River approximately two weeks after the murder.

Kevin Leon Cross, 25, Olsen's half brother, pleaded no contest in January to first-degree murder and was sentenced to life in prison.

Olsen had been scheduled for trial Wednesday to determine if he was mentally retarded. The District Attorney's Office was originally seeking the death penalty and Olsen's attorneys alleged he is mentally retarded because he has an IQ of 69, according to court papers.

District Attorney Emily Redman said she had expected the mental-retardation trial to go forward.

“We showed up this morning (Wednesday) in full anticipation of having a trial on the mental- retardation case, and at the last minute, were able to work it out,” Redman said.

According to Redman, Sheffield's father was contacted and agreed to the plea offer.

“His only request was that Olsen plead guilty instead of no contest,” Redman said.

Authorities said Sheffield was murdered because he was a witness in another criminal case against Cross.

Charges remain against two other people authorities said were involved in the crime. Melissa Michelle Poore, 27, was charged with assault and battery with a dangerous weapon. According to the sheriff's office, she brought Sheffield to the area where he was subsequently beaten and killed. Charged with being an accessory was John Edward Cook, 21. Authorities said he helped bury the body.