EL PASO - Two U.S. Border Patrol agents watching the Mexican boundary last year when they stopped a van carrying 743 pounds of marijuana. The driver fled back across the Rio Grande - with a gunshot wound in his buttocks.

Federal prosecutors convinced a jury in March that the agents had shot a defenseless man, then schemed to cover it up. Much of the evidence against them came from the drug runner, Osvaldo Aldrete-Davila, who reported the shooting to a friend at the Border Patrol in Arizona. Aldrete-Davila was given immunity from prosecution by the U.S. Attorney's Office.

On Thursday, the agents - Ignacio "Nacho" Ramos and Jose Alonso Compean - were sentenced to 11 years and 12 years, respectively, for offenses that included violating the smuggler's civil rights. Outraged supporters and anguished family members packed the courtroom, and many wept as the sentences were announced.

Outside the courthouse, members of the Minuteman Project, a group that opposes illegal immigration, carried "Free Nacho" placards.

"I'm just happy to be going home to my family tonight," Ramos said as he left the courtroom, surrounded by his attorneys and relatives. U.S. District Judge Kathleen Cardone agreed to let the men remain free until January, when they must report to prison.

The case has become a cause celebre among anti-immigration activists and advocates of stronger border security, who argue that it epitomizes the misplaced priorities of federal prosecutors as well as the absurd predicament of Border Patrol agents, who must fight heavily armed criminals while using little or no force. Among the rules broken by the agents, supporters note, was a policy forbidding agents from giving chase.

After Ramos and Compean were convicted, members of Congress demanded a review of the case; tens of thousands of people signed a petition supporting the agents and the efforts of the Border Patrol, which is vastly outgunned in its battle against narcotics cartels and human smuggling rings.

But Walter Boyaki, an attorney representing the smuggler, commended federal prosecutors for having the courage to carry on with a politically unpopular case, and he argued that if the agents had not been punished, it would have "put a bulls-eye on every illegal alien."

The agents were convicted of assault with a dangerous weapon and defacing a crime scene, as well as violating Aldrete-Davila's rights. One of the charges, using a firearm in the commission of a felony, carried a mandatory 10-year term. Lawyers for the agents successfully sought reduced sentences for the other counts, arguing that the men had solid records before the shooting, but Cardone gave Compean a longer sentence, finding him more culpable. She did not explain why.

"He's a good man who did his job," said Compean's attorney, Chris Antcliff. "What's got people so upset is the Draconian punishment in this case."

Added Andy Ramirez, head of Friends of the Border Patrol, a California group that has rallied support for the agents: "Why are they trying to protect this dope smuggler so badly? Why are they ruining the lives of two agents for doing their job?"

Federal prosecutors say the facts, which included evidence that Ramos and Compean did not report the shooting to their superiors, clearly warranted a tough prosecution. They say illegal-immigration opponents have spread lies and half-truths in a calculated campaign to turn the agents into martyrs.

"Federal agents do not get to shoot unarmed people as they are running away in the back and then lie about it and cover it up," said Johnny Sutton, U.S. attorney for the Western District of Texas. "It is very important for border agents to follow the laws they enforce, and in those rare instances where they do not do that, it is our job to bring them to justice."

Ramos and Compean said that they had gotten into a scuffle with Aldrete-Davila and that he appeared to be holding a gun. Aldrete-Davila said he was unarmed, that he had held up his hands in a surrender gesture; he said he fled in fear only after Compean tried to beat him with the end of his shotgun.

As he ran toward the Rio Grande, the Mexican citizen said, he felt a sharp sting and fell to the ground. When he touched his backside, he said, his hand came away bloody and he limped back to Mexico. Ballistics experts matched the bullet extracted from Aldrete-Davila's buttocks to Ramos' handgun.

He has sued the federal government for million, claiming permanent injuries.

The agents' description about what had occurred was contradicted by other agents who arrived on the scene.

After the trial, three jurors gave sworn statements saying that they felt pressure to convict, not understanding that a hung jury was a possibility. Attorneys for the agents sought a new trial, but their request was denied. They plan to appeal.