Kubwimana, the one in the pink sweatshirt, is said to have killed a child his own age. Like the vast majority of those implicated in the genocide, he belongs to the Hutu majority. He comes from the capital, Kigali, and has no idea whether his parents are alive or dead. "I'm not exactly sure what the other two are supposed to have done," says the social worker who introduces them: Innocent in the green sweatshirt and Nzayisenga in the blue. "But they've also been charged with genocide."
This is the first time in recorded history that children are being accused of mass murder. "You can't put a pretty gloss on this," says Ray Torres, of Unicef. "The crimes some of these kids have been charged with are the worst possible outrages."
In answer to questions about their involvement in last year's massacres, the boys say little other than "I didn't hurt anyone," or "It was a mistake that I was arrested." They whisper among themselves, but they have learnt from their elders not to proffer information that could lead to even more trouble.
The three boys are sitting on a blanket in one of the huts at Gitagata, a government-run juvenile detention centre in south-eastern Rwanda. They were recently brought here from the squalid, overcrowded prisons where they had been held since their arrests last year. By day, they lounge around a dusty yard where older boys strut about brandishing sticks to keep the younger ones in line. Who knows exactly what happens to them at night when they lie down on the concrete floors of the shacks that pass for dormitories? The staff stay out of the compound after dark.
Some 200 children under 14 were last year charged with crimes of genocide. More than 150 are held in Gitagata - the rest still languish among the general prison population. Under Rwandan law, they cannot be held criminally responsible, though what will happen to them is unclear. Unicef has paid for five lawyers to defend these 200 children. It is probably safer for them to be kept in detention. Were they to be released and returned to their communities, they might well be killed.
In addition to the under-14s, there are another thousand 14- to 18-year- olds who were last year charged with genocide. Unicef is lobbying for the death penalty not to be enacted for the teenagers. Their youth will also be taken into consideration when prison sentences are handed down.
To what extent did children voluntarily participate in last year's killings, and to what point were they coerced? In a situation where violence and hatred had become the norm for a certain section of the population, it does not seem unreasonable to suppose that, at one level, children were simply following the example of adults. According to some testimonies, children were handed machetes and ordered by parents or relatives to "finish off" severely wounded adults and children. Other reports tell of children accompanying their elders on killing sprees.
One is inclined to view these children as pariahs, whereas in a sense they are as much victims as those who have been attacked. Had they not been caught up in events beyond their control they would be playing in a schoolyard or on a football field rather than locked up in a prison compound. In the case of many of these children, guilt has been added to trauma, creating a burden of suffering they will bear throughout their lives.
It is difficult to grasp the enormity of the tragedy afflicting this small central African country no bigger than Wales. At least half a million people, mostly Tutsis but also moderate Hutus, were slaughtered between April and June last year. A third or more of those who died were children. In some of the largest mass graves, up to 45 per cent of the victims were children.
Unicef estimates that up to one million child survivors have been touched by the genocide. In a survey conducted by the fund near Kigali, 56 per cent of children had seen children taking part in the massacres, usually following the commands of adults, while 47 per cent had seen children kill other children. Two-thirds of all children witnessed massacres. One in five witnessed rape and sexual abuse. More than half of those questioned had seen family members being killed.
More than 95,000 children have either lost or been separated from their parents. Many of these children are now living in centres near the sprawling Hutu refugee populations in Zaire and Tanzania. Some 70,000 children are registered as unaccompanied (either orphaned or separated from their family) with the International Committee of the Red Cross, the largest number the organisation has had to deal with since the Second World War.
In centres all over Rwanda, there are children with terrible stories to tell. Samson Mazimpaka is a 13-year-old pupil at the Kadogo school for demobilised child soldiers in Butare, southern Rwanda.
"My family lived in Byumba, in the north," he explains. "In April last year, people came to our house. They were armed with machetes and said they were going to kill us. I escaped, but I learnt later that my father had been beheaded and my mother was thrown into the river. I was told the Interahamwe [Hutu militias] had tied up my two elder sisters and cut their legs off before throwing them alive into a pit with other bodies. I had two brothers but I don't know if they're alive. My grandfather is the only one in my family I know is still alive."
There are some 2,500 children at the Kadogo school. Some, as young as seven, were picked up by the Rwandan Patriotic Front as they moved into areas that had been ravaged by the Hutu militias. Though many of the older boys carried guns and participated in battles, most of the children at the Kadogo school were employed in supporting roles: they helped in the field kitchens, they polished boots and carried ammunition.
Samson's best friend is Vianney Nsanzabandi, another 13-year-old who, after the death of his family, also joined the RPF rebels as they advanced to victory over the forces of the rump government.
"We used to live in Gitarama. One day last April, young men who were neighbours came around and attacked us because we were Tutsis. I ran away. Afterwards, I was told that my parents, my brothers and sisters had been thrown alive into pit latrines. Before the killing started, we used to play with the Hutu children who lived near us. They were our friends. But they changed. They were running after other children with machetes and stones. I saw the boys who had been our friends killing other children."
What is amazing, given their experiences, is that these two former child soldiers should appear so well adjusted. Samson wants to be a journalist when he finishes his education, and Vianney wants to be a lorry driver. Both think their families' killers should be sent to prison, but neither wants the death penalty to be enforced.
"When they came here a few months ago, the children were all talking about revenge", explains director Frank Musonera, himself a former RPF soldier. "They sometimes have bad dreams at night and a few of them are still withdrawn, but they're beginning to understand that their problems aren't going to be solved by more violence".
Under the watchful eye of Frank Musonera and his team of soldiers-turned- teachers, the children at the Kadogo school are being brought back from the brink of terror. Though they are still wary of strangers and are nearly all afraid of having their photographs taken, most seem to be coping well.
Trauma manifests itself in different ways among these children. In addition to having nightmares, those who have witnessed atrocities display a wide range of symptoms from bedwetting to lack of concentration to aggressive behaviour. Psychologists believe these symptoms could form the prelude to all sorts of anti-social and violent conduct in later life.
Some, like 13-year old Saraphine Muhawenimana, one of 260 children at the Masaka orphanage near Kigali, are so disturbed that they need special treatment. Saraphine, who alternates between bouts of extreme lassitude and wild ranting, says she sometimes feels herself to be "umusazi", Kinyarwandan for "mad". All she wants is to find her brother from whom she became separated last year. Both her parents are dead.
Unicef has been training "trauma advisers" who will visit schools, children's centres and health clinics, and has helped the Rwandan government to establish a Trauma Recovery Centre in Kigali, which in the coming weeks will open a clinic for severely affected children. "Kids never erase the images of violence from their minds," explains Dr Leila Gupta, who came to Rwanda last year with a doctorate on grief and bereavement from the University of North Carolina. "Not if they've seen their father being beheaded or a pregnant woman being eviscerated. What we can do is help them gain a sense of control over these recurring images."
Dr Gupta has helped to produce two pamphlets, one aimed at parents and carers, Helping Children Heal Bad Memories, and another for children, entitled What Causes Bad Memories. These are shortly to be distributed in Rwanda.
"Kids establish their world view between the ages of six and 10," explains Dr Gupta. "They learn from their parents that the world is basically a benign place, that they've got self-worth and that people in authority are there to protect them. When something like the genocide happens, a kid's world view is completely shattered."
Along with organisations such as Save the Children Fund UK and Concern, the ICRC is helping to reunite children with their families. More than 10,000 reunions have taken place. But it is a slow process, beset by pitfalls. Sometimes children are too afraid to go back to their parents.
For some, such as 14-year-old Monique, there is a happy ending. After months in a refugee camp in Zaire, she has been reunited with her mother, whom she believed to be dead. When she arrived at the reunion in Gitarama, the girl held by the hand another little child she had met in the orphanage - the two had become inseparable. Monique's joy at seeing her mother was tempered by the discovery that both her father and brother were killed last year. But at least she had come home.