PHOENIX — A U.S. Supreme Court ruling Monday could prove to be good news for the mother of a Mexican teen hoping to sue the Border Patrol agent who shot her son at the Nogales line.

In an unsigned order, the justices directed the 5th Circuit Court of Appeals to take another look at its decision in a similar case, where a Border Patrol agent in Texas shot and killed a teen who was in a culvert on the Mexican side of the border. The justices said the appellate court needs to consider certain legal issues.

Potentially more significant, the Supreme Court said there was no basis for lower courts to conclude the Border Patrol agent is entitled to qualified immunity.

The ruling is a victory for the plaintiffs in that case: The appellate court had previously ruled they had no right to sue in U.S. courts. It gives the parents of Sergio Hernandez a new opportunity to make their case that Border Patrol agent Jesus Mesa Jr., who fired across the border, can be found liable.

Robert Hilliard, attorney for the victim’s family, told Capitol Media Services that what the justices wrote in connection with his case should also benefit Araceli Rodriguez, who is suing Border Patrol agent Lonnie Swartz over the 2010 shooting of her son in Nogales.

“Reviving our case, and determining no qualified immunity (for the Border Patrol agent) is the first step in what I believe will ultimately be constitutional protections to those shot and killed (in Mexico) by Border Patrol agents standing in the United States,” Hilliard said.

Swartz shot Jose Antonio Elena Rodriguez, who was standing on the Mexican side of the border at Nogales, through the border fence. Swartz has not denied the incident, but said the 16-year-old was throwing rocks at him.

After hearing oral arguments last year, the judges of the 9th Circuit decided not to rule whether Rodriguez’s case could go forward. Instead, they said they would wait to see how the Supreme Court ruled in the Texas case.

Swartz, through attorney Sean Chapman, has also raised the defense of qualified immunity. But U.S. District Court Judge Raner Collins, in an earlier ruling, reached the same conclusion as the Supreme Court in the Hernandez case, saying Swartz cannot claim qualified immunity for his actions, particularly as the agent could not have known at the time of the shooting that the victim was not a citizen.

There are several issues that are key in both cases.

Potentially the most crucial is whether a Fourth Amendment claim of wrongful search and seizure — in this case, encompassing wrongful death —can be brought in federal courts when the victim was killed in a foreign country.

The appellate court had concluded the Border Patrol agent was entitled to qualified immunity because Hernandez was “an alien who had no significant voluntary connection” to the United States.

The high court countered: “It is undisputed ... that Hernandez’s nationality and the extent of his ties to the United States were unknown to Mesa at the time of the shooting.”

Hilliard said those factors favor not only his client but also Rodriguez in her case against Swartz.

In Monday’s ruling, the justices also resurrected the claim that Hernandez’s Fifth Amendment rights were violated because he was deprived of life or liberty without “due process of law.”

If nothing else, Monday’s court action means it will likely be at least October — if not later — before the justices rule in the Texas case. And that keeps the civil lawsuit against Swartz on the back burner, even as a criminal trial against him is set to begin Oct. 12.