Masri's case is one of the 26 instances detailed in the Senate report when the CIA snared someone in its web of secret dungeons by mistake, realised its error after weeks or months of mistreatment and questioning, and then let them go. But the report does not recount what that mistake meant to Masri's life.

"I was stunned by the torture report," Gnjidic said. "They had known and privately admitted for years that they had made a mistake regarding Khalid," who is a German citizen.

And yet the CIA, which realised its error within weeks of Masri's January 2004 detention, remained silent - as did the Senate Intelligence Committee, which learned of the mistake in 2007.

"For a decade, a decade in which his life has been shattered, he'd asked for … an apology, an explanation, a chance to go ahead with his life," Gnjidic said.

"They knew this, they admitted this and they didn't share this with him? How cowardly must they be, how weak must they be, to fear apologising when they knew they were … wrong?"

Masri's incarceration totalled 35 days by CIA count - but closer to four months by Masri's. The Senate report does not discuss his treatment there, but Masri has previously insisted he was tortured. He has described being shackled to the ceiling naked, unable to sit for days, existing on nothing, in the dark - a scenario that appears to be common in the torture report. A European court ruled in 2012 that he'd been sodomised and drugged.

The shadow cast by the detention saw him labelled by German media as an "Islamist extremist". Neighbours shunned him. Potential employers turned him away.

A grocer and a mechanic before he was detained, he was arrested the first time in 2007 for setting fire to a store in a dispute over a broken iPod. His second arrest came when he attacked the mayor of Ulm in 2009, reportedly over the city's approval of a legal brothel permit.

But the truth of his case was evident just days after CIA agents stuffed Masri's head into a hood and chained him to the floor of an aircraft that took him from Europe to Afghanistan in January 2004. The CIA officers tasked with getting at his terror connections soon expressed doubts about whether he had any.

In emails contained in the Senate report, CIA officers in Afghanistan noted Masri, who'd been on a bus holiday to Macedonia, "seemed bewildered … adamant that (CIA) has the wrong person."

He was picked up, after 23 days of similarly pointless interrogation in Macedonia, because counterterrorist officers reported "al Masri knows key information that could assist in the capture of other al-Qaeda operatives."

Yet as the CIA became convinced it had the wrong man, the question became what to do with him. They eventually flew him back to Macedonia and dumped him on a roadside with €14,500 (about HK$132,000 at the time).

There were no consequences for those who made the mistakes.

CIA did have prison in Romania, official admits

After years of government denials, a top Romanian official has for the first time confirmed the CIA had "at least" one prison in the country.

Ioan Talpes, the former head of the country's intelligence service, said the CIA had "centres" in Romania, including a transit camp or compound where prisoners were kept before being moved to other locations.

He is the first Romanian official to confirm the information in the CIA torture report last week, which stated the existence of at least one "black site" in which prisoners were held and probably tortured.

Successive governments have spent years denying the rumours, even after last week's US Senate report said there had been a prison in Romania.

Talpes said the transit camp was set up following detailed discussions with Romanian authorities. He told Germany's there was one, possibly two locations in the country in which "it is probably that people were imprisoned and treated in an inhumane manner" between 2003 and 2006.

Talpes, 70, was head of Romania's foreign intelligence service SIE between 1992 and 1997. And for four years until 2004, was head of the president's office with responsibility for national security.

He said he had continuous discussions with CIA and US military officials about closer cooperation between them and Romania. The main tenet of the conversations was always about giving the CIA the ability to carry out its own activities, he added.

But he denied knowing where the CIA centres had been or that torture had been carried out in them, adding that Romania had "explicitly taken no interest in knowing what the CIA did there".

His country had been particularly keen at the beginning of negotiations to prove its willingness to cooperate in the hope that it would help it to achieve Nato membership. Romania finally joined Nato in March 2004.

"It was the Americans' business what they did in these places," Talpes said.

Dick Marty, appointed by the Council of Europe to investigate alleged illegal CIA activities in Europe, accused Romania in 2005 of hosting CIA prisons for terrorist suspects. The accusations were repeated by Amnesty International.

Khalid Sheikh Mohammed, the 9/11 chief planner, is one prisoner believed to have been held there.

Romania's former president Ion Illiescu said this week he had no knowledge of the CIA prisons. However Talpes said he had informed Illiescu himself in 2003 and 2004 that the Americans were carrying out "certain activities" on Romanian soil.