The day after the Day of the Dead, Taide Elena arranged flowers at her grandson’s grave in Nogales, Mexico.

The tightly packed graveyard was quiet, save a few Día de los Muertos latecomers, among them, a woman cleaning the neighboring grave. “Was yours the car accident next to the technical college?” the woman asked.

“No,” Elena said and her voice dropped. “A border patrol agent shot my grandson from the other side of the border.” She took a deep breath. “I hope that God forgives him, because we never will. He killed Toñito with 10 shots in the back. They’re in court now. Let’s see what God says.”

God, and also a jury, which is currently in deliberations and could deliver a verdict as soon as this week on a case that caused headlines nationwide and catapulted Elena’s personal loss into the center of America’s fierce debates over immigration and its border with Mexico.

Last week, Elena was in a Tucson, Arizona, courtroom, hearing quickfire testimony through slow Spanish translation in the trial of the man who killed her 16-year-old grandson.

José Antonio Elena Rodríguez was shot and killed by a border patrol officer, Lonnie Swartz, through three-and-a-half-inch slots in the steel fence dividing Nogales, Mexico, from Arizona on 10 April 2012. It’s been an arduous legal journey to get to this point. It took two and a half years for Swartz to be indicted, another three to go to trial, and the jury there found him not guilty of second-degree murder. They did not reach a verdict on the manslaughter charges last April, though, so now the US government prosecutor’s office has been working to prove both voluntary and involuntary manslaughter over the past four weeks.

The defense argued the reason Swartz fired the 16 rounds in 34 seconds was because he feared for his life. Why? Because of rocks coming over the international border fence. Rocks that many doubt Rodríguez had anything to do with.

James Tomsheck served as head of internal affairs at Customs and Border Patrol until 2014. During his eight years at the agency, José Antonio’s case was the only one that went to criminal court. The case still haunts him.

“If no guilty verdict is achieved in this trial, I believe it would be interpreted by frontline border patrol agents as open season on young Latino boys at the border who may be engaging in misconduct that does not in any way justify lethal force,” he said.

Relatives and supporters attend a monthly vigil in Nogales, Mexico held in honor of José Antonio Elena Rodríguez. Photograph: Richard Boren

Art Del Cueto, however, believes Swartz’s use of force was perfectly justified. “Rocks can kill you” he said, echoing Donald Trump’s assertion earlier this month as he sent thousands of US troops to the border.

Del Cueto is vice-president of the National Border Patrol Council, the union that was the first union to endorse Trump as a candidate, and which is funding the defense in this trial. They have brought an impressive roster of witnesses, such as Dr Cyril Wecht, who examined the autopsy notes that the Mexican forensic pathologist made, as well as JFK’s body immediately after his assassination. “The union is representing Lonnie Swartz because we believe he’s innocent. I believe Lonnie did the right thing,” Del Cueto said.

Many do not, arguing that Swartz was not under any kind of threat from anyone throwing rocks.

The day before closing statements, Elena took the stand as the final witness in the case and faced questions from the prosecuting attorney Mary Sue Feldmeier.

“How often did you see José Antonio?”

“Every day,” she said. “Including the day before he died.”

“And where did he live?”

“With me. In the home I raised my children and grandchildren in for 42 years.” She fought the picture of drugs and violence the defense had conjured with descriptions of an adobe and wooden house, laughing when asked it was fancy, “Lujoso? Pues, no,” she said.

The third question got to the point: And which hand did he favor? “He combed, ate, did everything with his left hand. It’s like he only had one hand.” Her love was apparent even through the monotone English interpreter. A couple of jurors laughed.

All of the models that the defense has developed allege that José Antonio was throwing rocks with his right hand.

While the impact of this case ripples far beyond the family, into border enforcement, the war on drugs and a rare opportunity for accountability within the largest policing agency in the country, for Elena, justice is simpler: Swartz should be in prison for murdering her grandson. While the jury make up their mind in the coming days, Elena will continue to light candles at the altar she made for her grandson. She is waiting to see what God – and an American jury – decides.