'Here, it's just rampant,' he said.

'I don't know exactly why. Maybe it's a character thing, it may be the culture of Rwanda, maybe the witnesses need to incriminate authorities of the previous regime.'

Rwanda's Hutu majority was in power in 1994 when the president's plane was shot out of the sky, triggering a three-month killing spree. International journalists reported on a Hutu campaign of hate, one that included lists of every Tutsi in the country, who were labelled 'cockroaches' in radio broadcasts and marked for extermination.

An ex-Tutsi rebel witness known as 'BBB' signed an affidavit saying he attended at least three meetings orchestrated by a Rwanda-based survivor's group, Ibuka, where witnesses plotted false testimony.

Another says he listened from his living room while an Ibuka representative dictated the evidence his wife was to give. In some cases, the prosecution paid witnesses, ostensibly for travel-related expenses.

'Witness G', a former leader of the Interahamwe, the Hutu militias blamed for carrying out the killings, admitted in court on October 24, 2005, that he received US$30,000 in cash from the prosecution, explaining it was a reward from the prosecution for helping build cases against Hutus.

Another Interahamwe leader, known as 'Witness T', admitted he received US$16,000 in cash.

'These payments were laundered through the United States government and were subject to approval and review by lawyer Neil Karbank of Aspen, Colorado,' states a motion filed by Mr Robinson asking the judges to order prosecutors to disclose payments they made to witnesses. The motion was rejected in August, when three judges decided 'an oral hearing to investigate these allegations would be no more than a fishing expedition'.

Stephen Rapp, a state prosecutor from Illinois who joined the tribunal in 2001 as its chief of prosecutions, admits prosecutors have a very difficult job unravelling the web of political influence in a demure culture with deep ethnic roots and tensions, where lying is not only tolerated but sometimes encouraged.

In Rwanda, as in most of Africa, time is not important, language is imprecise and familial relationships are confusing, making court testimony difficult.

'If you read the accounts of these individuals, it's not the kind of thing that any of us would know enough about to put words in people's mouths, about what really occurred, who was there and how this worked. This is a really Byzantine political situation,' he said.

To understand it, prosecutors rely on 'insiders'. In exchange for their testimony, prosecutors have promised to provide at least five 'insiders' - who each admit to war crimes, committing murders or ordering executions - with a new identity as well as at least two years of financial support for the war criminal and their families once they've been relocated somewhere in Europe.

All will serve their sentences in a European prison and enjoy European guidelines on parole. Some have even been promised plastic surgery once they've finished serving their sentence.

Mr Rapp admits Juvenal Uwilingiyimana, the former Rwandan agricultural minister and one-time minister for national parks and tourism, would have received a similar deal if he'd signed a statement and agreed to testify against his former colleagues.

Instead, on November 21, he disappeared. A month later, his badly decomposed body was pulled from a Belgian canal. Two weeks before he went missing, Uwilingiyimana allegedly wrote a letter to the prosecutors at the international court. In it, he spoke of threats levelled at him by two Canadian investigators working for the court, of pressure to provide false testimony that would 'demolish' key members of the Hutu government believed to be the masterminds behind a plan to wipe out the country's Tutsi minority.

'I do not wish to lie to please the investigators,' Uwilingiyimana allegedly wrote. 'I am prepared to assume all of the consequences set forth in detail by the investigators [Rejean] Tremblay and [Andre] Delvaux: I will be lynched, crushed, my body will be trampled on in the street and the dogs will piss on me [the terms used by the investigators].' Mr Rapp dismissed the letter as a fake and said investigators deny making any threats.

Uwilingiyimana was secretly indicted last summer for his role in helping prepare for the genocide, in which peasants took up hoes and machetes to kill more than 800,000 people in 100 days.

For nearly three months, Uwilingiyimana staved off arrest by travelling each weekday from his home in Brussels to Lille, in France, under the guise of attending a university course. In fact, he was being interrogated by tribunal investigators and was on the verge of landing a sweetheart deal in return for signing a 92-page question-and-answer-style statement that would be the basis for his insider testimony against key purported war criminals.

That is motive enough for desperate defendants to make him disappear, prosecutors say. But more than one defence lawyer claims Uwilingiyimana was going to testify on behalf of their clients.

Montreal lawyer John Philpot expected he would take the stand and help exonerate his client. Investigators working with Mr Robinson met with Uwilingiyimana on November 26, 2002, and December 4, 2003, and expected him to testify in Arusha refuting evidence given by one of the tribunal's 'insiders'.

'His death actually does more harm to us than the prosecution,' Mr Robinson said. Mr Rapp is adamant his investigators are neither building false cases, nor pressuring witnesses to lie.

'You don't gain anything if the insider sits there and tells you a whole pack of lies about what was going on. It's gotta be stuff that's consistent with the human rights reports that were happening at the time, with the people on the inside and the outside that you've had information from,' Mr Rapp said.

He also dismisses the fabrication allegations as a diversionary tactic by desperate defence lawyers.

'Those aren't legal arguments. They don't excuse murder, they don't excuse mass murder,' Mr Rapp said. 'It doesn't win the case. It may make some accused persons feel better to have that sort of argument, but it doesn't make the case.'