Her son died in Mexico from a bullet fired by a U.S. border agent. Seven years later, she waits for justice.

CIUDAD JUAREZ, Mexico.- The body of Sergio Adrian Hernández lay on the dry riverbed of the Rio Grande, just a few feet from the puddles of water that mark the border between the United States and Mexico.

A bullet fired by a U.S. Border Patrol agent on the U.S. side had hit the unarmed 15-year-old in the head. He collapsed on the Mexican side and died a few minutes later, at the foot of a bridge used for legal border crossings by millions of pedestrians and vehicles each year.

A sign on the crossing now reads: “Your mother and brothers you.”

Hernández was shot on June 7, 2010, and the case remains open. But the U.S. Supreme Court, the highest legal authority in the nation, will decide this month if the teenager's family has the right to sue the Border Patrol agent for the death.

“He didn't have a right to kill him just because he was Mexican and was on Mexican soil,” said Hernandez' mother, Maria Guadalupe Güereca. “Of course not!”

A divided Supreme Court

The boy's father, Jesus Hernández, 63 and a car wash attendant, said nothing on Feb. 21 of this year as he left the family's home on the southern edge of Ciudad Juarez, where the city disappears into the desert, in a neighborhood without paved streets or running water.

He found an isolated spot and knelt. And he prayed. “Lord, thy will be done.” As he did so, eight justices of the U.S. Supreme Court were hearing his lawyers' arguments in Washington.

The Supreme Court is not ruling on whether the Border Patrol agent was wrong to fire at Hernández. It will rule only on whether the family of a foreign citizen killed in another country by a U.S. official has the right to sue him in a U.S. court.

Only eight of the nine Supreme Court justices heard the arguments in February because Justice Neil Gorsuch had not yet been confirmed by the Senate.

The justices appeared to be deeply divided on the issue. The progressive justices appeared to believe that the death took place in no-man's land because it was not clear where U.S. jurisdiction ended and Mexican jurisdiction began. Conservative justices appeared to fear that a Hernandez family victory would open the door to thousands of lawsuits for deaths caused by U.S. forces anywhere in the world.

The Hernandez family's lawyers argued that the U.S. Constitution is valid in the region where the two countries meet – and that therefore the Fourth and Fifth Amendments should protect their son from police brutality and official immunity.

“Right now the border is a free kill zone," said attorney Robert Hilliard, who presented the family's case to the Supreme Court. “They are free to kill a Mexican citizen in Mexican territory without consequences.”

“There's anarchy because the Constitution has no effect on security forces when they are on U.S. territory,” the lawyer added. “They are free to kill a Mexican citizen in Mexican territory, but also a U.S. citizen on Mexican territory.”

Six shot to death on Mexican territory

“When I thought everything was lost, the lawyer called me,” said Hernández' mother. He said: “You know what, ma'am? … Your son's case is going to the Supreme Court.”

That's how Güereca, 60, learned in October that the high court had agreed to hear the appeal to rulings by federal district and appeals courts that had turned down the lawsuit. She was getting off a bus after a nearly 370 mile trip from the border town of Nogales.

She had been in Nogales for an annual protest against fatal Border Patrol shootings of people on the Mexican side of the border. “There's the case of Sergio, of Jose Antonio, of Anastasio, in Tamaulipas. There are many, there are many,” she said.

The American Civil Liberties Union has reported at least 53 deaths caused by U.S. Customs and Border Patrol agents between 2010 and 2016. Hernández and five others were shot to death on Mexican territory. Agents claimed the victims were throwing rocks at them from the other side.

The future of the other cases hangs on the Supreme Court ruling in the Hernández-Güereca case later this month.

One version: A kid's game

Hernandez' mother said she did not even put her shoes on, just ran “like a crazy woman” to the border crossing after she heard about the shooting. She saw her son's body on the side of the river, from a distance, and a Mexican official told her the teenager had just been pronounced dead.

The boy's father had to rush in from further away, hitchhiking in cars and trucks. By the time he got to the scene, only the stains of the tragedy remained.

From the start, the family claimed the boy was simply playing with friends on the river, running to touch the border fence and then running back to the Mexican side. They denied that he had crossed the fence, was throwing rocks at the Border Patrol agent or helping to smuggle immigrants.

“And anyhow, even if he had thrown a rock, what's a rock against a bullet,” said the mother, who has been separated from the boy's father for more than a decade. She sold her house to pay off debts and now lives with a daughter.

Another version: Migrant trafficking

The day after the boy's death, on June 8, 2010, an FBI statement said the Border Patrol agent who fired had run into a group of young smugglers who surrounded him and threw rocks at him.

One day later, a cellphone video recorded from the border bridge and provided to Univision contradicted the U.S. version. The video showed the youths did not surround the U.S. agent, and that Hernández did not throw rocks before he was shot.

The U.S. Department of Justice and lawyers for the Border Patrol agent argue that he was justified to fire in self-defense. Defense documents in the case allege that Hernández was trafficking migrants and claim the agent has immunity.

Univision Noticias requested an interview with the agent's lawyers several times but never received a reply.

The agent, Jesús Mesa Jr., was not dismissed by the Border Patrol. The Customs and Border Protection agency would not say whether he continues to work for the agency, saying it does not comment on cases under litigation.

Added fuel for U.S.-Mexico tensions

The Mexican government can do little about the case. It has filed several complaints with U.S. Courts, but it cannot put the Border Patrol agent on trial unless the U.S. Government extradites him. Mexican authorities have said their northern neighbor is not respecting Hernández' basic human rights.

The Supreme Court ruling will come at a tense time in U.S.-Mexico relations, following the election of President Donald Trump and his harsh immigration and border policies.

Hernández's funeral drew a large crowd, and the anger unleashed by the death of the teenager known as Keko are still visible.

A sign saying “Rest in peace Keko” now marks the house where he lived, and four big yellow letters spell Keko next to the riverbed where he died.

His father carries photos of Hernández and newspaper clips about his case in his backpack as he heads to work. He drives on an empty and dusty road, from where he can see the twin cities of Ciudad Juárez in Mexico and El Paso in Texas. The border is invisible, and the two cities look like one huge urban sprawl.

Tears fill his eyes whenever he talks about his son, and he says he's ashamed that he never spent enough time with the boy. “There's been problems in my life, but nothing tortures me like this one,” he said.

The boy's mother seems to stare into the distance a lot, tired after so many hours of crying. She once dreamed that her son told her to stop crying for him, and now tries not to shed tears.

At the cemetery, sitting on the ading tomb of someone named Alvaro, she dabs a tear with the same blue rag she has been using to clear her son's tombstone of the desert dust that covers much of Ciudad Juarez. She is here every Monday.

“I talk to him,” she said. “And I ask him, what were you doing there? Why did you have to go there?”