The attorney for a Border Patrol agent who killed a teen in 2012 wants to block jurors from hearing a prosecution witness testify he believes the shooting was unjustified.

In new court filings Wednesday, Sean Chapman said the question of whether Lonnie Swartz had reason to shoot Jose Antonio Elena Rodriguez through the border fence in Nogales is one for the jury — not the government’s expert witness — to decide.

Chapman also wants U.S. District Court Judge Raner Collins to limit the testimony of other law-enforcement witnesses who were involved in the incident. He said there’s nothing wrong with them telling jurors what they saw.

“But they may not offer opinion as to whether Agent Swartz’s use of force complied with Border Patrol training or policy,” he told Collins.

Swartz is charged with second-degree murder.

Swartz admits to the shooting, but said Elena Rodriguez was throwing rocks at him from across the border. Chapman said the teen was doing so because he had been on the U.S. side of the border prior to the shooting, “probably acting as a smuggler or a scout.”

Prosecutors argue all that is legally irrelevant to the question of whether Swartz was justified in firing through the fence. An autopsy found the teen dead on the Sonoran side of the border with 10 shots in his back.

In the latest legal filing, Chapman told Collins he got a letter from prosecutors saying they intend to call Alan Foraker as a “use of force” expert in a bid to persuade jurors that Swartz’s use of his gun was contrary to the Border Patrol’s training and policies regarding use of deadly force.

Specifically, Chapman said, prosecutors said Foraker will testify that the use of force “was neither reasonable nor necessary,” that Elena Rodriguez did not have the opportunity and intent to inflict serious bodily harm on Swartz or anyone else, and that Swartz, who said rocks were being thrown at him, “should have made use of available cover” and that it was “neither reasonable nor necessary” for the agent to approach the border fence.

Chapman said that Foraker, assuming he really is an expert witness, can legally talk to jurors about policies, procedures and appropriate uses of force within those policies. What he cannot do, the attorney said, is give his legal conclusion on whether what Swartz did was lawful.

Chapman also is trying to get Collins to rein in what other officers at the scene may say during the trial, which is set to begin Oct. 12.

“While it clearly (is) permissible for agents to testify as to what actions they took, testimony regarding their interpretation of use-of-force policy is inappropriate and should be precluded,” the defense attorney wrote.

According to Chapman, prosecutors have identified a witness who will suggest to the jury that Elena Rodriguez was not throwing rocks at Swartz or other agents.

The defense attorney renewed his effort to have jurors hear from a Nogales resident who will provide some information he said links Elena Rodriguez to drug-smuggling operations. In addition, Chapman said a defense investigator has evidence that markings found on the dead teen’s shoes are “very similar” to what would occur if a smuggler were climbing the border fence.

“This information ... debunks the government’s theory that the decedent was innocently walking home (and not throwing rocks) at the time of the shooting,” Chapman wrote. “It completes the story, and supports the theory of the defense” that Swartz was acting in self-defense.

Assistant U.S. Attorney Wallace Kleindienst, in his own legal filings, told Collins that proposed testimony is both irrelevant and inflammatory and would “prejudice the jury against the government.”

Chapman chided the prosecutor’s claim. “The mere fact that the evidence is potentially harmful to the government’s case makes it neither irrelevant nor overly prejudicial,” he wrote.