An Oklahoma man charged as an accessory after the fact in the murder of Australian baseball player Christopher Lane has pleaded guilty to hiding the gun used to kill the athlete.

Oddesse Barnes, 23, pleaded guilty in a deal with Stephens County prosecutors and agreed to testify against Chancey Luna and Michael Jones, who are facing first-degree murder charges.

Barnes would serve 12 years for the crime, followed by 13 years of probation for hiding the handgun thought to have been used to kill Lane, prosecutors said.

Teenagers Luna and Jones will be tried separately in April.

The two are accused of tracking Melbourne resident Lane, who police said was shot in the back on August 16, 2013, while jogging in Duncan, about 130 kilometres south of Oklahoma City.

Lane was a student at East Central University in Ada and had been jogging in the small town when he was shot.

He was on a baseball scholarship at the university and was two weeks away from celebrating his 23rd birthday.

Prosecutors said the pair decided to kill someone "for the fun of it". Lawyers for the teenagers have denied that accusation.

A third teenager in the car with the pair at the time of the incident has agreed to testify against the two.

The teens, who were 17 and 16 at the time of Lane's death, face possible sentences of life in prison without parole if convicted.

People who commit capital crimes before age 18 cannot be sentenced to death in the United States.

Reuters