The boys were racing up the concrete embankment to touch the barbed-wire fence on the US side, then racing back down, when Border Patrol agent Jesus Mesa shot Sergio in the head. Photograph: (AFP)
Sergio Hernandez, 15, was playing around with friends on the dry riverbed of the Rio Grande which separates the two countries
Sergio Hernandez died at 15, shot dead by policeman Jesus Mesa. His would have been a story of American violence both tragic and banal if the victim had not been in Mexico and the shooter in the US.
The thorny legal question raised by the cross-border homicide heads to the US Supreme Court on Tuesday.
At issue is whether the teen's family has the constitutional right to sue Mesa, a Border Patrol agent, in US courts.
The Supreme Court takes up the case amid a deeply divisive national debate on President Donald Trump's vow to build a US wall on the border with Mexico to stem illegal immigration.
The shooting occurred June 7, 2010. Hernandez was playing around with three friends in the dry riverbed of the Rio Grande that separates the Mexican city of Ciudad Juarez from its Texan neighbor El Paso.
Mesa later explained that Hernandez and his friends had refused to obey his order to stop the game and had thrown rocks at him. Mesa left the scene without helping his victim
The four friends were racing up the concrete embankment to touch the barbed-wire fence on the US side, and racing back down. The unmarked border line runs through the middle of the culvert.
Their game bothered Mesa, who was patrolling the area on bicycle. He shot Hernandez in the head, and the teen died just 60 feet (18 meters) from the border on Mexican soil.
The Border Patrol agent later explained that Hernandez and his friends had refused to obey his order to stop the game and had thrown rocks at him.
Mesa left the scene without helping his victim, accompanied by colleagues who had come to give him back-up.
According to the family of the victim, the teen was shot while unarmed and presented no danger.
The case sparked protests in Ciudad Juarez and a diplomatic mini-crisis between the neighboring countries, with Mexico's then-president Felipe Calderon demanding a "profound and impartial" investigation by the Obama administration.
The previous week, another Mexican teenager, Anastasio Hernandez Rojas, had died after being beaten and shocked with a Taser by border police at the southwest crossing between Tijuana and the US city of San Diego.
It was in this context of repeated US official violence against Mexican nationals at the border that the parents of Hernandez decided to sue Mesa, accusing him of violating the Fourth Amendment of the US Constitution, which bars unjustified deadly force.
Their lawsuit for unlawful use of lethal force also cites the Fifth Amendment, which among other provisions says that a life cannot be taken without the "due process of law."
The Fifth Circuit Court of Appeals in New Orleans ultimately upheld a decision to dismiss the case, stating that US courts had no jurisdiction since the victim was Mexican and died in Mexico.
In the appeal, the New Orleans court decided that the complaint of unlawful use of lethal force could not be applied.
Rights group Amnesty International called the ruling "intolerable" and "in violation of basic principles of international law."
According to Bob Hilliard, an attorney with Hilliard, Munoz, & Gonzales, the firm representing the Hernandez family before the Supreme Court, US border patrols have fatally shot at least eight Mexicans between 2006 and 2016 in cross-border incidents.
"Innocent Mexican nationals have been murdered with no ability to speak through the court system to the person who committed a crime," he said.
His partner, Jose Luis Munoz, pointed out the case has broad implications.
"Beyond politics, this case is about humanity," he told AFP.
"Human worth is not determined by place of birth and justice is not determined by where a life ends -- especially a young life cut short when a US law enforcement agent, standing inside the US and governed by this country's constitutional constraints, pulls the trigger."
After lengthy hesitation, the Supreme Court decided last October to hear the case, which has gathered numerous arguments in support of the parties.
The US federal government is backing Mesa, warning that authorization of such lawsuits could "significantly disrupt the ability of the political branches to respond to foreign situations involving" US national interests.
The Mexican government has warned that blocking the case could damage US-Mexican relations.
"Applying US law in this case would not interfere with operations of the Mexican government within Mexico," it said in a court brief.
"On the contrary, providing an adequate and effective remedy would show appropriate respect for Mexico's sovereignty on its own territory and for the rights of its nationals."'