Murat Kurnaz, who spent five years in the Guantanamo Bay prison camp without charge, has asked for an apology from Frank-Walter Steinmeier before the German foreign minister's expected accession to the presidency next February.

Steinmeier was chief-of-staff under Chancellor Gerhard Schröder while Kurnaz was being tortured and interrogated at Guantanamo between 2002 and 2006. According to a later European Parliament investigation, Steinmeier turned down a US offer to release the inmate back to Germany as early as 2002, when the CIA and the country's intelligence agency, the BND, knew he was innocent.

Kurnaz, now 34, was eventually released in 2006 under Schröder's successor Angela Merkel and now lives with his family in Bremen.

"To this day Frank-Walter Steinmeier has not approached me, to this day he has not apologized," Kurnaz told the "taz" newspaper on Monday via his lawyer Bernhard Docke. "He should clear his register of sins before becoming president." It was still, he said, an "open wound, a boundless disappointment to be left deserted in my need by Germany."

"Such a gesture is still owed, and we don't want to rule out that Steinmeier - following further reflection - might come to a different and better conclusion," Docke told DW. "We don't want to give up hope."

Tortured for years

Kurnaz, born in Germany with Turkish citizenship, was travelling in Pakistan in November 2001 to study Islam when he was arrested during a routine check by local security forces. He was then handed over - in exchange for a bounty - to the US army.

Then aged 19, he was interrogated in Kandahar, Afghanistan, before being transferred to Guantanamo in January 2002, where he was to spend the next five years of his life with no charge.

"American interrogators [in Kandahar] asked me the same questions for several weeks: Where is Osama bin Laden? Was I with Al Qaeda?" Kurnaz wrote in a "New York Times" article published in 2012. "No, I told them, I was not with Al Qaeda. No, I had no idea where bin Laden was. I begged the interrogators to please call Germany and find out who I was.

"During their interrogations, they dunked my head under water and punched me in the stomach," he continued. "At one point, I was chained to the ceiling of a building and hung by my hands for days. A doctor sometimes checked if I was O.K.; then I would be strung up again. The pain was unbearable."

The torture was intensified in the prison camp on Cuba. "There were more beatings, endless solitary confinement, freezing temperatures and extreme heat, days of forced sleeplessness," Kurnaz wrote. "I told my story over and over - my name, my family, why I was in Pakistan. Nothing I said satisfied them. I realized my interrogators were not interested in the truth."

Diplomatic abrogation

The German government was initially informed of Kurnaz's arrest in 2002, but told Docke that it couldn't intervene because of his Turkish citizenship. The Turkish government, for its part, refused to get involved because Kurnaz did not live in Turkey.

Nevertheless, the BND exchanged information on Kurnaz with the CIA, and in September 2002 two German intelligence agents were allowed to question him in Guantanamo, (Kurnaz himself was not allowed to speak to a lawyer until 2004).

According to the European Parliament inquiry on CIA activities released in 2007, both the CIA and the BND concluded that Kurnaz was innocent in 2002, and offered to release him back to Germany - an offer that Steinmeier was instrumental in turning down, calling instead for him to be released to Turkey, who again refused. (The inquiry noted that Steinmeier also turned down requests to testify, as did Klaus-Dieter Fritsche, coordinator of Germany's intelligence services, and BND president Ernst Uhrlau.)

Steinmeier's calculations

Docke said it had been "more a political decision" not to accede to the US release request, and that Steinmeier, as chief of staff, would certainly have made the final decision in consultation with the heads of Germany's intelligence agencies.

Docke also dismissed the question of Kurnaz's nationality as a factor, since it was clear that his client had his entire social circle in Germany - which was why the US wanted to release him there. "Germany could have said, 'of course we'll take him, regardless of his nationality, and we're glad we make this humanitarian gesture' - namely save someone from torture and the stripping of his rights," he said.

"Steinmeier never questioned that he helped make this decision," Docke added. "He just said that it was the right decision, because Kurnaz was a security risk. But that wasn't true, because the unanimous opinion in October 2002 was that Kurnaz was firstly innocent and secondly not dangerous."

Steinmeier himself was unrepentant after the report was made public. "I wouldn't make a different decision today," he told "Der Spiegel" in 2007, when he was foreign minister in Merkel's first cabinet. "You only have to imagine what would happen if there had been an attack, and afterwards it emerged that we could have prevented it."

Nine years later, that position doesn't seem to have changed - the Foreign Ministry did not respond to a DW request for a statement on Wednesday. Kurnaz has never received any kind of compensation or apology for his treatment, either from the US or Germany.