An aircraft technician saw a detainee shackled to the floor of a US plane at Shannon airport, a seminar on extraordinary rendition was told yesterday.
The claim came from retired Army officer and anti-war campaigner Edward Horgan, and was based on information he received from a third party.
He said he was told the technician had seen a man in an orange boilersuit shackled in this way in the plane a year ago. The technician had not made this public.
Mr Horgan appealed to workers at Shannon who had observed people being transported through Shannon in this way to come forward.
The seminar heard international experts say that it was not necessary for a plane to actually be carrying a detainee in order for an investigation to be justified by international law.
"The Government should investigate the entire itinerary of the plane," said Michael O'Flaherty, a member of the UN Human Rights Committee. It could be returning from having brought a detainee to another country.
He said it was not enough to accept assurances. The US had said at the UN that it did not accept assurances from other countries at face value but carried out its own investigations.
He said a problem arose with different understandings of what constituted torture. "For example, 'water-boarding' is torture according to the UN, but not according to certain states. What is the value of assurances if we don't know what words mean?"
Colm Ó Cuanacháin, secretary general of Amnesty's Irish section, said research conducted for Amnesty by Lansdowne Market Research had revealed that 76 per cent of respondents thought the Government should be checking US flights through Shannon.
Dr Vindodh Jaichand, deputy director of the Irish Centre for Human Rights, congratulated the Government on its categorical assurances that no rendition was taking place through Shannon.
"But reassurances, diplomatic or otherwise, do not take away people's suspicions. People feel actions are taking place on the margins of legality. I implore the US to do more than offer diplomatic assurances and allay the fears."