“My analysis of those papers has removed any shred of doubt as to the accuracy of statements made in our application” for victim status, he said.

Some of what took place here is already known. According to eclassified U.S. documents, Nashiri was threatened with a mock execution by power drill and handgun early in his seven-month stay at Stare Kiejkuty. Abu Zubaydah was waterboarded and subjected to other so-called “enhanced interrogation techniques.”

Other prisoners were very likely held here and treated in a way that Polish law prohibits.

Khalid Sheik Mohammed, the Pakistani man accused of masterminding the Sept. 11, 2001, terrorist attacks, was waterboarded 183 times in March 2003, declassified Bush-era documents have revealed. That treatment came at a time he was probably in Poland, said Irmina Pacho, of the Helsinki Foundation’s “strategic litigation” program. But Mohammed is representing himself at Guantánamo, so there’s no way lawyers can plead for him here.

It’s difficult to gauge the likelihood that all facts will be made public.

The Polish political elite is clearly ambivalent about prosecuting former officials, and the U.S. government has stonewalled all known requests for assistance, Polish lawyers say.

At Guantánamo, the U.S. government has insisted that information about Nashiri’s treatment be kept secret. His Pentagon defense attorneys and a group of American news organizations are challenging the idea that Nashiri’s treatment must be considered “classified” and kept secret.

The military commission judge will consider the issue at Guantánamo next week during hearings in the 9/11 case. Poland’s president, Bronislaw Komorowski, called in May 2011 for a “thorough investigation” rather than excuses about “loyalty to an ally.” But four months later he refused to release his predecessor, Aleksander Kwasniewski, from his pledge to secrecy on state security matters when the prosecutor wanted to question him.

Kwasniewski, who in 2008 denied that there was ever a secret CIA prison in Poland, opposes the prosecution. In an interview with McClatchy, he said that if anyone were to be prosecuted, it should be Americans, not Poles. “Calling to account someone in Poland” for cooperating with the U.S. is “inappropriate,” he said.

Leszek Miller, the left-of-center prime minister at the time the CIA center was operating, has refused to comment on the secret prison. But Donald Tusk, the right-of-center current prime minister, talks tough. “This is not the 19th century, and this is not some Bantu-stan,” he said in late March, after Siemiatkowski was indicted. “This case has to be resolved. Let there be no doubt about that either in Poland or on the other side of the ocean.”

For Tusk, the moment of truth is nigh. Last month, the European Court of Human Rights ordered Poland to explain by Sept. 5 why Nashiri and Abu Zubaydah have been given victim status and to provide the court with all agreements that pertain to the setting up of what the court called “a secret CIA prison” on Polish territory.

Still, there’s much that’s unknown about what happened in the Markus Wolf villa: the role of outside contractors in the prison’s day-to-day operations, the discussions between intelligence agencies that led to the establishment of the prison and what the Poles received in return, if anything, for allowing the black site to operate.