IN THE summer of 1988, when its revolution was nearly a decade old and the disastrous war with Iraq was winding down, the Iranian government killed around 5,000 political prisoners. The event is not particularly well known, partly because Iran went to considerable effort to make sure this was so, and partly because there was so much going on elsewhere at the time: the Soviet Union began pulling out of Afghanistan in May and a year later the Berlin Wall came down. A tribunal sitting in London until June 22nd is attempting to fill in the gaps, hearing testimony from survivors of the purge and from the relatives of those who went missing. The killing was ordered by a fatwa issued by Ayatollah Ruhollah Khomeini, who became Supreme Leader of Iran after the revolution. It was relentless and efficient. Prisoners, including women and teenagers, were loaded onto forklift trucks and hanged from cranes and beams in groups of five or six at half-hourly intervals all day long. Others were killed by firing squad. Those not executed were subjected to torture. The victims were intellectuals, students, left-wingers, members of the People's Mojahedin Organisation of Iran (MEK), other opposition parties and ethnic and religious minorities. Many had originally been sentenced for non-violent offences such as distributing newspapers and leaflets, taking part in demonstrations or collecting funds for prisoners' families, according to a report published by Amnesty International, an NGO, in 1990. The tribunal in London, which has no legal standing, will hear from 60 witnesses in total. They have come from the many countries where they live in exile and some asked not to be identified because they fear for the safety of relatives still in Iran. They describe prisons in which torture was routinely used to extract information, gather more names of people to arrest, and also to make prisoners repent and publicly repudiate their political and religious affiliations and beliefs. One witness said that one of his cellmates, a boy of 16, was raped by guards every night. Siavash Daneshvar, who was arrested in 1982 for being a member of Kurdistan's Kumele party, described rooms underneath the wards at Evin prison from which could be heard the cries of prisoners being tortured at all hours. “They also had ‘coffins' where prisoners stayed in for two, three, five or more months,” he said. Rahman Darkeshideh, who was arrested at 16 for possessing written slogans against the war, spent eight years in prison, including three in solitary confinement. “It was dark 24 hours a day. I had to relieve myself in the same cup I used for my tea," he said. "I will suffer physically and mentally for the rest of my life.” These testimonies, translated simultaneously into English, corroborated what was already known of the executions. In 2001 Grand Ayatollah Hossein Ali Montazeri, former designated successor to Khomeini, published a memoir which contains details of the 1988 massacre, including a copy of Khomeini's fatwa calling for the execution of all Mojahedins as “fighters against God” and all leftists as “apostates from Islam.” “There is a coherence amongst all the testimonies. They confirm the same story and match what was already known,” said Eric David, professor of public international law at Brussels University.

Iran had killed a large number of political prisoners throughout the 1980s, so why the sudden increase in 1988? The witnesses' testimonies suggest that the regime was worried about the large number of unrepentant political prisoners due to be released after the end of the war with Iraq, and so decided to purge its prisons of troublesome elements once and for all.

Witnesses described how, in the months preceding the massacre, they were questioned and separated according to their political and religious beliefs, and moved across various prisons. Then they were called one-by-one in front of a makeshift court made up of an Islamic judge, a state prosecutor and a representative of the Ministry of Intelligence. They were asked: “Are you a Muslim”, “Do you pray?”, “What is your political affiliation?” and “Do you recant your beliefs and political activities?” If their answers didn't satisfy the court they were sent for execution. Many must have had no idea why they were sent to the gallows. A witness told the commission that one of the clerics was holding his son on his lap. The little boy said: “Dear Papa, please also execute this one.”

Families were informed of the deaths months after they took place and were never told where their bodies were buried. “Four months after my brother's death, my father was called to Evin prison and told that his son had been an apostate and there was no place in this world for him and no place in the other world either,” said Lawdan Bazargan.

The tribunal, which has enthusiastic backing from Archbishop Desmond Tutu, has no power to do anything bar publicising the testimony of witnesses. A second tribunal will then convene in The Hague at the end of October. Neither gathering is likely to concern the people who arranged the killings too much. But at least they remedy what the relatives of victims mind about most—the forgetting of what happened one summer almost a quarter of a century ago.