Some 800,000 Rwandans were slaughtered in just 100 days during the 1994 genocide.
Rwanda has set up numerous memorials to the genocide
The Rwandan government and the United Nations are trying to bring those responsible to justice using different methods and both have their flaws.
How did the genocide happen?
Rwanda has always been divided between ethnic Hutus, who make up 85% of the population and the Tutsi minority which formed the traditional elite.
In 1994, the Hutu government was desperately trying to stop the advance of Tutsi rebels.
In April, a plane carrying the Hutu president was shot down. Within hours, some members of the government, including the prime minister, organised Hutu militias across the country to systematically kill Tutsis.
Checkpoints were set up at which anyone whose identity card showed they were Tutsi was killed; either shot or more often hacked to death with machetes.
Neighbours killed their neighbours and those moderate Hutus who refused to take part were also slaughtered.
Even nuns and priests have been found guilty of taking part in the genocide.
What did the international community do?
The world did little to stop the massacres but afterwards the UN set up an international court in the Tanzanian town of Arusha to try the ringleaders.
French troops in Rwanda failed to stop the genocide
Fourteen years after the genocide, at a cost of more than half a billion dollars, the court has so far convicted 34 people and acquitted six. Twenty-three remain on trial and eight trials have yet to begin.
The ICTR is due to wind up by the end of 2009.
The Rwandan government has condemned it for being inefficient, corrupt and not doing enough to protect witnesses.
It has also complained that some of those who took part in the genocide were employed by defence teams.
One of these has since gone on trial.
The Arusha tribunal was also hit by a strike by defence lawyers, saying they were not given the same treatment as prosecutors.
How has the UN responded to the criticism?
The tribunal's original chief prosecutor, Carla Del Ponte, said the Rwandan government was trying to stop her investigating crimes allegedly committed by the Tutsi rebels in 1994 before they came to power.
Nevertheless, in 2003, she was replaced and left to concentrate on her other duties at the International Tribunal for the former Yugoslavia.
Extra judges have also been appointed in a bid to speed up the trials.
The United States has helped unearth some alleged ringleaders hiding in various African countries by offering a $5m reward for information leading to their capture.
What about the ordinary members of the militias?
Those lower down the militia hierarchy are being tried in Rwanda but there are problems here, too.
Because of the way the genocide was carried out, huge numbers of people were involved.
Several thousand people have been tried by criminal courts and mass trials have been held.
But some 120,000 people were arrested after the genocide, taking Rwanda's prisons to bursting point.
The government said it could take 100 years for all these people to be tried and released about 20,000 charged with lesser crimes in 2003.
Another 30,000 were freed in 2004.
These were people who had pleaded guilty and already spent longer - nine years - awaiting trial than their sentence would have been if they were eventually convicted.
But genocide survivor groups were still furious.
How is Rwanda addressing this problem?
Traditional community courts, called gacaca, meaning the small lawn where village elders congregate to solve disputes, have been introduced to speed up the trial process.
Suspects are taken to the villages where they allegedly committed their crimes and confronted directly by their accusers.
A key part of the gacaca process is that released prisoners must ask forgiveness for their crimes.
The trials are not overseen by legally qualified judges but local people respected for their integrity.
Some called it "mob justice" as suspects do not have access to lawyers and have to represent themselves, but Human Rights Watch agreed that it was necessary despite the legal shortcomings.
However, there have been numerous recent reports of genocide survivors being killed before they give evidence to these courts.
More than a decade after the mass slaughter, the genocide continues to loom large over Rwanda.