In a landmark congression-al hearing Tuesday, former Guantánamo detainee Murat Kurnaz described abuses he said he endured while in US custody – among them electric shock, simulated drowning, and days spent chained by his arms to the ceiling of an airplane hangar.

Lawmakers were also provided with recently declassified reports, which show that US and German intelligence agencies had determined as early as 2002 that Mr. Kurnaz had no known links to terrorism. Still, he was held for four more years.

Kurnaz's testimony to Congress, via videolink, as well as a report released Wednesday showing that FBI agents were troubled by the harsh interrogations at Guantánamo, are the latest signs of growing concerns in the United States about the prison camp, which has become emblematic of what many around the world see as American excess in the war on terrorism.

Nowhere was the disquiet more evident than in lawmakers' responses. Politicians on both sides of the aisle, who had once accepted Pentagon assurances that those held at Guantánamo were the "worst of the worst," reacted with outrage and regret to Kurnaz's statements, which were broadcast from his hometown of Bremen, Germany.

Rep. William Delahunt (D) of Massachusetts, who chaired the hearing, said Kurnaz's account – denied by Pentagon officials – was something "every patriotic American should find repugnant."

Even Dana Rohrabacher, a stalwart Republican and defender of the Guantánamo prison system, voiced concern, saying, "It could be after seeing those buildings go down and 3,000 of our people were slaughtered, we moved so quickly that some mistakes were made.... The documents seem to indicate mistakes were made in this case."

Among the documents given to lawmakers is a May 2003 report from Brittain Mallow, the commanding general at the time of the Criminal Investigation Task Force, a Pentagon intelligence unit that interrogates and collects information on detainees. It notes, "CITF is not aware of evidence that Kurnaz was or is a member of al-Qaida."

Another memo, from German intelligence agents who interrogated Kurnaz under CIA supervision in 2002, reads, "USA considers Murat Kurnaz's innocence to be proven."

'Innocent' but not set free

The papers are only the latest batch to surface in Kurnaz's case, where the record clearly shows that he was repeatedly designated an enemy combatant despite evidence of his innocence.

Much of the testimony given by Kurnaz, the first former Guantánamo detainee to appear before Congress, focused on his treatment at Kandahar Air Base in Afghanistan, where he was taken after being arrested in Pakistan in December 2001. While there, he said was subjected to "water treatment," which involved having his head dunked in a water-filled bucket. "They stick my head in the water and at the same time they punched me in the stomach so I had to inhale the water," he said, using English he picked up in detention.

Kurnaz, dressed in a black satin pinstriped suit and seated next to his lawyer, also claimed he was routinely beaten, subjected to extreme temperatures, and chained by his arms to a ceiling, adding that "the pain from this treatment was beyond belief."

Having grown up in Germany, which was schooled in the rule of law by the US, he said he "couldn't believe Americans would do these kinds of things."

Commander Jeffrey Gordon, a Pentagon spokesman, refused to comment on his treatment, but said in a written statement, "The abuses Mr. Kurnaz alleges are not only unsubstantiated and implausible, they are simply outlandish."

The Bush administration has repeatedly insisted that those held at Guantánamo are enemy combatants that pose a threat to the US. Earlier this month, for example, a former detainee from Kuwait was found to have participated in a suicide bombing in Iraq.

Why he was kept for four more years

Two months into his detention, in February 2002, Kurnaz was moved from Afghanistan to Guantánamo.

In September of that year, three German intelligent agents were invited to the island to interrogate him under CIA supervision.

According to transcripts of testimony they later gave before Germany's parliament, the US and German intelligence agencies agreed that there was no evidence of links to terrorism and cleared him for release. But German officials, wary of looking soft on terrorism after a Hamburg cell was found to have played a key role in the 9/11 attacks a year earlier, blocked his return.

Apparently as a result, Kurnaz stayed at Guantánamo for another four years. The Pentagon summary from his August 2004 tribunal proceedings show that the key charge against him was that he was "a close associate with, and planned to travel to Pakistan with" a man named Selcuk Bilgin, who, the Pentagon claimed, "later engaged in a suicide bombing."

These allegations turned out to be untrue: Mr. Bilgin is living in Germany with his wife and children, and has never been charged with any crime, according to German police.

It has since come to light that at least three classified documents in Kurnaz's Pentagon file pointed to his innocence, but because detainees do not have access to classified evidence, he had no way of knowing this.

Pentagon support for his detention

US District Judge Joyce Hens Green, who delivered a 2005 ruling on Kurnaz's claim, and those of 62 other prisoners challenging the legality of the Combatant Status Review Tribunals, found that Kurnaz's case was an illustration of the "fundamental unfairness" of the system, particularly its reliance on "classified information not disclosed to the detainees." (Much of the ruling was itself was classified until recently.)

Kurnaz was finally released in August 2006 after Angela Merkel took over as German chancellor and personally pressed his case with President Bush.

The Pentagon maintains that it was justified in holding Kurnaz. "We have a significant amount of information, both classified and declassified to support his detention," Commander Gordon said. Noting that many of the documents related to Kurnaz's case are heavily redacted, he added, "It would be misguided to draw a whole picture based on bits and pieces of information."

But members of the House Foreign Affairs subcommittee, which hosted Tuesday's hearing, are calling for an investigation.

Key exhibit in Supreme Court review

While Kurnaz's case has only recently gained wide attention in the US, he has long been a household name in Europe, particularly in Germany, where – as in many other nations – there are deep misgivings about Guantánamo.

A 25-country poll by the BBC World Service and GlobeScan found that 69 percent disapprove of the prison and of US treatment of detainees.

A growing number of US lawmakers have been calling for the camp to be shut down. Opponents warn that doing so could return terrorists to the battlefield.

The outcome of the debate may hinge, in large part, on the findings of the Supreme Court, which is currently weighing a challenge to the legality of the Guantánamo Tribunals – a case in which Kurnaz is emerging as a key exhibit.

The former detainee hopes his testimony on Capitol Hill will help tip the scales. "I hope they will take it seriously and close the place down," he told the Monitor.