The appeals court opinion was not a good one for a federal police agency trying to overcome a ­trigger-happy ­reputation.

A three-judge panel of the U.S. Court of Appeals for the 5th Circuit ruled that the family of a 15-year-old boy can sue a Border Patrol agent who killed the teen. At the time, the boy was in Mexico and the officer was in the United States.

The June 2010 cross-border shooting by agent Jesus Mesa Jr. killed Sergio Adrian Hernandez Guereca. Mesa’s attorney said Sergio was throwing rocks at the officer, an accusation denied by the family’s attorney.

Last week, the court sided with the family, saying “no reasonable officer would have understood agent Mesa’s alleged conduct to be lawful. . . . It does not take a court ruling for an official to know that no concept of reasonableness could justify the unprovoked shooting of another person.”

This was yet another blow to U.S. Customs and Border Protection, the Border Patrol’s parent agency. It has been working to repair its image after a string of reports about abusive, sometimes fatal, actions by its employees.

Working for the Border Patrol can be a difficult and dangerous gig. Just last month, a man accused of killing agent Brian Terry in 2010 was extradited from Mexico. Lately the officers have had to deal with a flow of unaccompanied children and families from Guatemala, El Salvador and Honduras.

No one denies the important work the officers do. They protect the border from the undocumented and illegal activities. But when agents use excessive force, that can be illegal, too.

At least 29 people have died since January 2010 as a result of encounters with CBP, according to the American Civil Liberties Union. “Ten of these individuals were confirmed U.S. citizens, and six, including three minors, were standing in Mexico when fatally shot,” the ACLU said. “At least nine people were allegedly throwing rocks when CBP personnel responded with lethal force.”

Shawn Moran, vice president of the National Border Patrol Council, said he fears the court ruling, if it stands, could make agents “hesitate to defend themselves when under attack due to concern of a civil suit, thus leaving them vulnerable to serious injury or death.”

The labor organization “does not condone the abuse of illegal aliens, in any form,” Moran added. “Border Patrol agents work every day to protect this nation’s borders. This same work includes rescuing illegal aliens, treating their injuries and providing them food and shelter in numbers far beyond what any other aid group has ever accomplished for illegal aliens. . . . This is not to say there are not those within our ranks that have committed crimes against illegal aliens. Those crimes should be thoroughly investigated and if found guilty, the criminals punished.”

But CBP in too many cases has not thoroughly investigated allegations against its officers, allowing those who might be guilty to go unpunished.

“CBP officials rarely take action against the alleged perpetrators of abuse,” according to a report by the American Immigration Council. It reviewed 809 abuse complaints lodged against the Border Patrol from January 2009 to January 2012. “It is astonishing,” the council said, “that, among those cases in which a formal decision was issued, 97 percent resulted in ‘No Action Taken,’ ” which is the title of the report. The council acknowledges that some cases might not have merit.

Mesa was not charged with a crime or disciplined in connection with the teen’s killing.

CBP’s transparency deficiency has made matters worse. It feeds the perception the organization has something to hide. In fact, it did hide from the public a critical February 2013 report the agency commissioned from the Police Executive Research Forum until the Los Angeles Times reported on it a year later.

CBP finally released the report in May along with a revised use of force policy handbook. Commissioner R. Gil Kerlikowske, who took office in March, said “this release and, most importantly, the policy and training changes they represent are the beginning of a continuous review of our responsibility to only use force when it is necessary to protect people.”

The PERF report said some CBP investigations into the use of deadly force by its officers demonstrated a “lack of diligence. . . . It is not clear that CBP consistently and thoroughly reviews all use of deadly force incidents.”

That was not good for the head of CBP’s internal affairs unit, who was removed last month.

The agency is working on its tarnished image, and Rep. Lucille Roybal-Allard (D-Calif.), who has been a CBP critic, praised Kerlikowske for taking “several important steps to enhance CBP’s transparency and accountability.”

But, she pointed out: “None of the officers and agents involved in these deaths have faced any consequences. The American people deserve a higher standard of conduct and professionalism from our nation’s largest law enforcement agency.”

Twitter: @JoeDavidsonWP

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