MILAN — Italy’s highest court upheld guilty verdicts Tuesday against the final three U.S. defendants in the 2003 extraordinary rendition kidnapping of an Egyptian terror suspect.

The decision, after a series of trials spanning six and a half years, brought to a close the only prosecution to date against the Bush administration’s practice of abducting terror suspects and moving them to third countries that permitted torture.

The court upheld guilty verdicts and confirmed the seven-year sentence against the CIA’s former Rome station chief Jeff Castelli and six-year sentence against two others identified as CIA agents. All three had been acquitted in the original trial due to diplomatic immunity.

The three are among 26 Americans, mostly CIA agents, who have been found guilty in absentia of kidnapping Milan cleric Osama Moustafa Hassan Nasr, known as Abu Omar, in broad daylight from a Milan street on Feb. 17, 2003. They received sentences of six to nine years. Italy later pardoned the only military defendant.

Though lower courts found the CIA had worked alongside Italian secret services, the high court last month acquitted Italy’s former head of military intelligence and the former head of counter-intelligence, as well as three Italian agents, after the Constitutional Court ruled key testimony was classified as state secret.

Human Rights Watch, Amnesty International and European human rights activists monitored the trial throughout.

“It is really a seminal case. It set a very important precedent that unfortunately has not been followed yet by any other countries,” said Judith Sunderland, senior Western Europe researcher for Human Rights Watch. “We certainly hold it as an example how a national judiciary can in fact get to the bottom of an unlawful rendition.”

The case set Italy’s institutions against each other from the start, with a dogged prosecution facing off against a state that showed reluctance to prosecute agents of its American allies, with U.S. bases established during the Cold War still on Italian soil.

Four successive Italian governments argued that evidence against the Italians, most critically that demonstrating contact with foreign agents, was covered by state secret, with flip-flop decisions delaying proceedings and overturning previous rulings until the end.

The Italian Justice Ministry never responded to prosecution requests for extradition of American suspects to Italy, and issued an Interpol notice for an arrest warrant for only one defendant, former CIA base chief Robert Seldon Lady, who received the stiffest sentence of nine years. He was briefly detained in Panama last summer as a result, and has since asked Italy’s president for a pardon.

The case against the Americans relied primarily on detective work, including photocopies of passports from Italian hotels that showed reconnaissance meetings and intercepts of cellular data to show proximity to the actual kidnapping as well as movements from Milan to Aviano Air Force base, from where Nasr was put on board a plane for Ramstein Air Base in Germany. From there, he was transferred to Egypt, where he says he was tortured.

Milan Prosecutor Armando Spataro, who led the investigation and prosecution, said Tuesday’s verdict “was confirmation that our investigation was correct and that the evidence was solid. This crime was not covered by diplomatic immunity.”

Despite having the main Italian convictions overturned, Spataro said the overall outcome “was positive.”

“This was the only case in the world that brought to light this practice,” he said.

Alessia Sorgato, who was one of four court-appointed defense lawyers, complained the U.S. government had not responded to requests for help to defend their clients.

None of the court-appointed lawyers had any contact with their clients. U.S. officials only granted two of the defendants permission to seek their own counsel toward the end of the trial: the military defendant Col. Joseph Romano, who was head of security at Aviano, and Sabrina De Sousa, an India-born U.S. diplomat whose involvement in the trial has prevented her from visiting family outside of the United States.