A Border Patrol agent charged in the shooting death of a Mexican teen across the border six year ago cannot be cross-examined about his military record when his trial begins in Tucson in March, a federal judge has ruled.

Chief U.S. District Court Judge Raner C. Collins in a decision Thursday sided with defense lawyers for Lonnie Ray Swartz who do not want their client's Army service and personnel records introduced as evidence.

Prosecutors have said the records include an arrest for desertion but Swartz' lawyers say he was never was actually in custody and went on his own to an Oklahoma military base to formally leave the Army.

Swartz has pleaded not guilty to one charge of second-degree murder in the 2012 death of 16-year-old Jose Antonio Elena Rodriguez of Mexico. He is accused of killing the youth in 2012 by firing through a border fence from Nogales, Arizona, into Nogales, Sonora, Mexico.

Swartz has said Rodriguez threw rocks at him, endangering his life. The teen's family denies that claim, saying he was walking home after playing basketball with friends.

Swartz reportedly enlisted in the military in 1995 when he was 19 and went AWOL two months later. Prosecutors have said he was picked up in Las Vegas in October 1997 and discharged in lieu of trial by court-martial four months later.

They claim Swartz omitted that information when he applied to work for the Border Patrol and said only that her served a month in the Army before quitting.

"The jury should be apprised of those statements in evaluating his credibility on the witness stand," prosecutors said in request for the documents to be made available to jurors.

Defense attorney Sean Chapman has said Swartz's military history has no bearing on whether he fired his weapon with criminal intent in the death of Rodriguez.

The judge said in his ruling that Swartz' military records are more than 10 years old and that the defense had a reasonable argument made "in good faith."

Collins ruled that prosecutors can use 15 documents from Border Patrol employee records.

The agent, who is on administrative leave from his job, also faces a civil rights lawsuit that the ACLU filed on behalf of the boy's mother.

Earlier this week, defense lawyers asked the judge to allow jurors to make a nighttime visit to the crime scene of the international boundary. It was unclear when a ruling will be issued on that request.

Chapman argued that jurors are unlikely to be familiar with the border fence, located on a steep hill fronted by narrow streets where the shooting occurred.