WASHINGTON – The Supreme Court agreed Tuesday to consider for the second time whether a U.S. Border Patrol agent is liable for the cross-border shooting death of a 15-year-old Mexican boy.

The justices granted the case, first heard in 2017, after two federal appeals courts issued conflicting rulings. The U.S. Court of Appeals for the Fifth Circuit dismissed the claim for damages against the agent, but a Ninth Circuit appeals court came to the opposite conclusion in another cross-border shooting.

It will be the second Supreme Court go-round for Border Patrol agent Jesus Mesa and the family of Sergio Adrián Hernández Güereca following the 2010 incident, in which Mesa fired from El Paso, Texas, killing the boy with a single shot to the head.

The family's lawyers say Hernández was playing with three friends in the 33-foot-wide concrete culvert separating El Paso and Ciudad Juárez, Mexico. Mesa's lawyers say he responded to a group of suspected illegal aliens throwing rocks at Border Patrol agents. Cellphone videos appeared to show that Hernández was hiding beneath a train trestle when he was shot in the head.

At issue is a Supreme Court precedent that allows private individuals to sue federal employees for constitutional violations in specific instances. In this case, it depends on whether Hernández lacks constitutional protection because he was in Mexico, as lower courts have consistently ruled, or whether Mesa is liable because the gun was fired in the United States.

A Mexican court could have tried Mesa in that country, but the U.S. government refused extradition.

"The deadly practice of agents standing in the United States and shooting innocent kids across the border must be stopped," the family's attorney, Bob Hilliard, said in a statement Tuesday. "It’s never right. It’s never constitutional. This is one of those times when morality and our U.S. Constitution line up perfectly.”

The first time the case was heard, the high court called it "a disturbing incident resulting in a heartbreaking loss of life" but sent it back to the Fifth Circuit for further review. The case had been watched closely in part because of President Donald Trump's fledgling effort to build a wall along the U.S.-Mexico border.

Associate Justice Clarence Thomas dissented from the 2017 ruling and said Mesa should be cleared. Associate Justices Ruth Bader Ginsburg and Stephen Breyer also dissented, arguing the boy should be covered by the Fourth Amendment's guarantee of security.

In a related case decided in 2017, the high court ruled that U.S. officials cannot be held personally liable for the detention and harsh treatment of illegal immigrants in the days after the Sept. 11 terrorist attacks. The justices then told the appeals court to take that into consideration in the cross-border case.

A 2013 investigation by The Arizona Republic, part of the USA TODAY Network, found that Border Patrol agents and Customs and Border Protection officers killed at least 42 people – including at least 13 Americans – in an eight-year period. At the time, none of the agents or officers responsible were publicly known to have faced consequences.