A separate case is pending that involves four Spanish citizens who were held at the U.S. military prison at Guantánamo Bay, Cuba, where they say they were subjected to sexual assault, forced nakedness, death threats, severe beatings and constant interrogations without lawyers.

Judges in both cases sent letters last May asking U.S. government lawyers whether they're investigating these allegations; if they were, any U.S. cases probably would supersede the Spanish ones. To date, according to the center, the U.S. hasn't responded.

"As much as they're moving slowly, these are cases that have a pretty good shot of proceeding, particularly in face of inaction in the U.S.," said Katherine Gallagher, a senior staff attorney with the center.

The prosecutions would mark a turnaround for Spain, which under a conservative government earlier in the decade was one of the staunchest European supporters of the Bush administration's war on terrorism.

Lithuania and Poland — where prosecutors are considering bringing war crimes charges against the country's former president and former prime minister over allegations of secret prisons — are part of what former Defense Secretary Donald H. Rumsfeld famously called the "new" Europe. It was Rumsfeld's way of distinguishing traditional powers such as France, which opposed the war on terrorism, from the continent's younger democracies, which were among Bush's early backers.

"They were strong allies, and the obstacles were very strong in the beginning," said Wolfgang Kaleck, a civil rights attorney and the general secretary of the nonprofit European Center for Constitutional and Human Rights. "At a certain point, important people within those countries made the decision to start these investigations. This is already a big step."

Last month, the new British prime minister, David Cameron, announced a judicial inquiry into whether British intelligence services had participated in the abuse of terrorism suspects. Cameron's decision followed a public outcry over the case of Binyam Mohamed, an Ethiopian national living in Britain who charges that British authorities knew that CIA agents were torturing him in Pakistan, Morocco, Afghanistan and Guantánamo and did nothing to stop it.

"Our reputation as a country that believes in human rights, justice, fairness and the rule of law ... risks being tarnished," Cameron said.

Months earlier, when the British government bowed to a court ruling and published classified details about how Mohamed was treated, U.S. intelligence officials had said that the decision was "not helpful, and we deeply regret it."

As a result, Cameron said that British courts wouldn't disclose such evidence during the inquiry and suggested that foreign witnesses — such as current and former CIA officers — won't be called to testify.

"There are foreign-policy and diplomacy considerations in how far they're willing to push this," said Siems of the ACLU.

However, Siems said, the cases weren't toothless, particularly if they result in arrest warrants for U.S. officials, as they did in Italy's conviction of the CIA officers.

"Ultimately, that's what you could end up with: an international map with various judgments against U.S. officials which are subject to enforcement if they travel," Siems said. "That would put us in pretty dubious company."