Maria Guadalupe Güereca, 60, leaves her house in her car to visit the grave of her son Sergio Adrián Hernández Güereca at the Jardines del Recuerdo cemetery in Juarez, Mexico. (Yuri Cortez/AFP via Getty Images)

The gun was fired in the United States. The bullet stopped 60 feet away in Mexico — tragically, in the head of a 15-year-old boy named Sergio Adrián Hernández Güereca.

Border patrol agent Jesus Mesa Jr. pulled the trigger that day six years ago in the wide concrete culvert that separates El Paso from Juarez, Mexico. On Tuesday, the Supreme Court will consider whether the Constitution gives Hernández’s parents the right to sue Mesa in American courts for killing their son.

The case comes amid a time of increasing tension and controversy over how this country polices the daily churn along the border, where essential international commerce takes place alongside narcotics trafficking and human smuggling.

[Border patrol chief quits after clashes with union]

Courts have struggled to deal with the national security and foreign policy implications of the case, and the Supreme Court’s precedents.

(Outreach Strategists, LLC)

If Hernández had been killed inside the United States, then the case could proceed. Or if he had been a U.S. citizen, it would not have mattered that Mesa was on one side of the border and he was on the other.

But the courts so far in Hernández’s case have said the Constitution does not reach across the border — even 60 feet — to give rights to those without a previous connection to the United States.

To find otherwise, Judge Edith H. Jones wrote when the U.S. Court of Appeals for the 5th Circuit considered the question, would “create a breathtaking expansion of federal court authority … and would have severely adverse consequences for the conduct of American foreign affairs.”

But lawyers for the parents say there must be recourse for killing an unarmed teenager playing with his friends. Halting the case before it is even tried, their brief tells the Supreme Court, erects “a legal no-man’s land in which federal agents can kill innocent civilians with impunity.

“This court should make clear that our border is not an on/off switch for the Constitution’s most fundamental protections.”

There have been more than 40 killings by border patrol agents, according to an Arizona Republic investigation cited in Hernández’s parents’ brief. Their lawyer, Corpus Christi, Tex., trial attorney Robert C. Hilliard, said there have been 10 cross-border shootings, with six deaths.

Hernández’s death attracted more than the usual headlines, partly because of the boy’s age and partly because cellphone videos of the incident contradicted the border patrol’s initial explanations.

The agency said Mesa was under attack from rock-throwing youths on the other side of the culvert that follows the Rio Grande as he tried to break up an attempt to enter the United States.

But the videos showed Hernández and the others apparently playing a child’s game in which they ran up the steep concrete bank, touched the high fence on the U.S. side, and ran back to Mexico. In the footage, Mesa, patrolling in the culvert on a bike, grabbed one of the boys. While holding on, Mesa fired his gun at Hernández. The deadly shot came as Hernández peered from behind a pillar of the Paso Del Norte Bridge, which connects the two countries.

Two U.S. investigations found there were no grounds on which to charge or reprimand Mesa. He was indicted on a charge of murder in Mexico, but the United States refused to extradite him.

Mesa’s attorney, Randolph J. Ortega, questions the version of the events contained in the family’s lawsuit. But for the proceedings in the Supreme Court, the allegations against Mesa are to be accepted by the justices as they consider whether the case can be heard in U.S. courts.

Both sides say there is precedent to support them as the court considers whether constitutional rights apply to a non-U. S. citizen for events that occurred outside this country.

In a 1990 case called United States v. Verdugo-Urquidez, a four-member plurality of the court ruled that the Constitution does not protect noncitizens from the prohibition against unreasonable searches and seizures by government agents beyond the border.

But in a 2008 case, Boumediene v. Bush, regarding the rights of those held at Guantanamo Bay, the court took what is called a “functional’ approach to border issues. It said the totality of the circumstances, not just location, must be considered.

Key to both issues was Justice Anthony M. Kennedy. He wrote the majority opinion in the Boumediene case, and wrote a concurring opinion in the Verdugo-Urquidez case that provided a majority for the outcome.

The U.S. government is supporting Mesa. “An injury inflicted by the United States on a foreign citizen in another country’s sovereign territory is, by definition, an incident with international implications,” the government said in its brief.

Courts should not insert themselves into “such sensitive matters.”

But Mexico is urging the Supreme Court to step in. It said the decisions by the lower courts “failed to take due account of the binding international human rights obligations that the United States has voluntarily undertaken to Mexico and its nationals.”

Its brief continues: “Those include, among other things, the fundamental right not to be arbitrarily deprived of life and the right to an adequate remedy when that right has been violated.”

Hilliard, Hernández’s parents’ attorney, said the renewed national commitment to secure the borders and the increased militarization of the border patrol means there will be more such cases. The U.S. Court of Appeals for the 9th Circuit has said another cross-border shooting case may proceed. It is on hold awaiting the Supreme Court’s action.

Attempts to bring Hernández’s mother to Washington for Tuesday’s hearing were unsuccessful. Mesa’s attorney Ortega said his client will not be there either and has not attended any of the lower court proceedings.

Mesa has continued to work as a border agent but has moved away from El Paso because of death threats, Ortega said. “He wants to know as little as possible” about the court battles surrounding his action, Ortega said.