Babak Zamanian, a lanky 23-year-old student of mining engineering, vividly remembers the last time he bellowed slogans denouncing President Mahmoud Ahmadinejad.
On a bitterly cold winter's day in December 2006, he led a crowd of students in chanting 'Death to the dictator!' as the Iranian leader delivered a speech at Amirkabir University of Technology, a hotbed of student protest in Tehran.
A few weeks later, Zamanian was blindfolded by authorities and tossed into Section 209, the notorious solitary confinement block in Evin Prison run by the Ministry of Intelligence and Security. That began a four-month ordeal of physical and psychological abuse by interrogators determined to have him confess on camera to collaborating with the CIA. When he refused, he says, they tied his hands behind his back and beat him black and blue.
'They harbour a 'teach them a lesson' vindictiveness,' he says. 'They are very, very brutal.'
Zamanian is among thousands of political activists and journalists freed on bail but banned from leaving the country. Yet, he can count himself lucky; a young man and woman were recently reported to have died in custody, though the authorities announced the deaths as suicides.
A visibly nervous Zamanian recounts the litany of abuse and torture at a rendezvous in a downtown Tehran cafe, all the while fearing that he might have been followed.