By Keith Coffman

DENVER (Reuters) - A policeman charged with murder in the shooting death of a man last year in a rural Colorado community shot the victim in the back when he posed no threat to the officer, court papers unsealed on Friday showed.

James Ashby, 31, is charged with second-degree murder in the October slaying of Jack Jacquez, 27, in the small farming town of Rocky Ford, about 135 miles southeast of Denver.

Details about the shooting emerged after Ashby was bound over for trial by Otero County District Court Judge Mark MacDonnell following a preliminary hearing on Thursday.

According to an arrest warrant affidavit filed by an agent with the Colorado Bureau of Investigation, Ashby lied in his accounts of what led up to the confrontation and about the shooting itself.

Ashby told investigators he was patrolling in his car when he saw Jacquez riding his skateboard in the road. Ashby said he pulled up alongside him and asked him what he was doing.

Ashby said Jacquez responded with a profanity but a member of the public who was doing a "ride-along" in the officer's vehicle at the time later told detectives he heard the victim say only that he was going home, the affidavit said.

The officer then pursued Jacquez to a house the victim shared with his mother and entered the property on foot, the court papers said.

Ashby told detectives he thought Jacquez was trespassing or burglarizing the residence and that Jacquez advanced on him out of the darkness wielding a baseball bat. Ashby said he only fired in self-defense, the affidavit said.

An autopsy concluded Jacquez died from a single gunshot that entered his back, severing his spinal cord and passing through his heart and a lung.

Investigators who re-created the scene found there was enough ambient light inside the house to call Ashby's account into question, the court papers said.

Police said Jacquez had likely been holding a baseball bat but that his back was turned to the officer. The affidavit said the physical evidence indicated Jacquez had been facing away from Ashby when he was shot and was not a threat.

Ashby was fired from the police department in Rocky Ford, population about 4,000, following his arrest in November. He is free on a $150,000 bond and is set to be arraigned on Feb. 12, according to the Otero County Clerk's office.

(Reporting by Keith Coffman; Editing by Daniel Wallis and Bill Trott)