FILE - In this Dec. 4, 2017, file photo, a portrait of 16-year-old Mexican youth Jose Antonio Elena Rodriguez, who was shot and killed in Nogales, Sonora, Mexico, is displayed on the Nogales street where he was killed that runs parallel with the U.S. border. Closing arguments are expected in Tucson, Ariz., this week in the trial of U.S. Border Patrol agent Lonnie Swartz, charged in the 2012 fatal shooting 16-year-old Jose Antonio Elena Rodriguez across the Mexican border. (AP Photo/Anita Snow, file)

TUCSON, Ariz. - Jurors in Arizona deliberated Tuesday without reaching a verdict in the trial of a U.S. Border Patrol agent charged with second-degree murder in the cross-border shooting of a teenager who was throwing rocks at authorities during a drug-smuggling attempt.

The deliberations began earlier in the day in federal court in Tucson, Arizona, in the case against agent Lonnie Swartz, who fired 16 shots in 2012 through a 20-foot (6-meter) fence that sits on an embankment above Mexico's Calle Internacional, a Nogales street lined with homes and small businesses.

Deliberations are set to resume Wednesday after the month-long trial.

The case marks the rare prosecution of an on-duty federal officer in a fatal shooting from the U.S. into Mexico.

Prosecutors acknowledged during the trial that 16-year-old Jose Antonio Elena Rodriguez was throwing rocks across the border into the U.S. but say Swartz responded with an unreasonable amount of force.

During closing arguments Monday, Assistant U.S. Attorney Wallace Heath Kleindienst said Swartz "was fed up with being rocked" after being targeted in at least six other attacks.

"He was angry with those people who had been throwing rocks against the fence," Kleindienst said.

"It was not about eliminating a threat, because there was no threat," he said. "It was about eliminating a human being."

Jurors temporarily left the deliberation room Tuesday to sit in the courtroom as a clerk read back the agent's testimony about being targeted in at least six rock-throwing incidents.

The Border Patrol came under close scrutiny during the Obama administration for allegations involving excessive use of force.

Customs and Border Protection, its parent agency, reported 55 incidents in which employees used firearms from Oct. 1, 2011, to Sept. 30, 2012. The number of incidents fell to 17 for the same period five years later.

Defence attorney Sean Chapman said in his closing argument that there was "not a scintilla of evidence" that Swartz was angry or fed up.

He said Swartz shot because he was trying to protect himself and his fellow agents during a drug operation.

"From his first day in the Border Patrol, it had been ingrained in him that rocks were dangerous," Chapman said.

District Judge Raner Collins has told the jury it can downgrade the charge against Swartz to voluntary or involuntary manslaughter during its deliberations.

The trial played out as President Donald Trump called for National Guard troops to be sent to the Mexican border to free Border Patrol agents to concentrate on stopping drugs and people from illegally entering the United States.

The killing of Elena Rodriguez was felt deeply in the twin communities of Nogales, where about 20,000 people live on the Arizona side and about 300,000 in Mexico. The communities are linked by family members, trade and culture and have long been referred to locally as "Ambos Nogales" — "Both Nogales" in Spanish.

Swartz pleaded not guilty after being indicted by a federal grand jury in 2015 and has been free on his own recognizance. The Border Patrol has not said if he was still receiving his salary.

The agent, who has been on administrative leave pending the trial's outcome, testified that he remembered little of what happened.

News from © The Associated Press, 2018