The Bush administration aggressively expanded an already-existing rendition program. Human rights advocates believe U.S. agents transported terrorism suspects to the custody of countries including Egypt, Jordan, Morocco, Libya and Syria.
The exact number of people is unknown. In a speech in 2007, former CIA Director Michael Hayden said that fewer than 100 had been targets of the program since the Sept. 11, 2001, attacks, according to Human Rights Watch.
The Obama administration has cracked down on what it calls abusive tactics, moving to shut down the detention facility at Guantanamo, end secret detentions and investigate harsh interrogation methods.
But U.S. officials have said spy agencies will continue renditions, albeit with more oversight, because they are an effective tool for fighting terrorism, especially in lawless regions. Critics have warned that the combined effect of overseas prosecution and the administration's new policies will damage the morale of CIA officers and impede them from doing an already dangerous job.
On Wednesday, the CIA declined to comment, as it has throughout the case.
Other U.S. officials expressed disappointment.
"We are disappointed by the verdicts against the Americans and Italians charged in Milan for their alleged involvement in the case involving Egyptian cleric Abu Omar," said Ian C. Kelly, a State Department spokesman. He said he expects defense lawyers to appeal.
A Pentagon spokesman said the judge should have dismissed charges against Air Force Lt. Col. Joseph Romano, who was in charge of security at the Aviano base. The Pentagon had argued that Romano was shielded by a NATO treaty that protects the U.S. military from foreign prosecution.
Spartaro said he probably will appeal the acquittals of the three Americans and the verdicts setting aside charges against the Italians.
Because Judge Magi convicted most of the American suspects, it was surprising that he cited diplomatic immunity for his acquittals of Castelli and the two other officials based at the U.S. embassy in Rome. Prosecutors had argued that immunity did not apply.
But analysts said the judge apparently made the decision because the case against the top officials in Rome lacked the abundant physical evidence accumulated against those directly involved.
"It was rather surprising because it seemed from the investigation that Castelli was the person who inspired the operation," said Guido Olimpio, author of a book about the case called "Operation Hotel California" and Washington correspondent for Italy's Corriere della Sera newspaper.
"But the evidence was the strongest involving the kidnapping itself and those who took part. The important fact is that it is the first verdict of its kind. Usually spies from a friendly nation are expelled, not prosecuted."
McClatchy-Tribune News Service.