The court, known as the Extraordinary African Chambers, was created for Mr. Habré. Unusually, it applies the laws of Senegal to judge the former head of state of a country more than 2,000 miles away for acts that occurred in that country.

The presiding judge is from Burkina Faso, and the other two are from Senegal. They must decide if the many crimes presented in court can be imputed to Mr. Habré. Once seen by the West as a bulwark against Col. Muammar el-Qaddafi of Libya, Mr. Habré received arms and advice from France, Israel and the United States.

The only comparable case in Africa involved Charles Taylor, the former president of Liberia, who was convicted by a United Nations-backed tribunal for crimes committed in Sierra Leone.

Yet what perhaps most distinguishes the special court in Dakar is that it was created with political support from the African Union, which has long complained that Africans were being singled out for prosecution by the International Criminal Court in The Hague. After much legal wrangling, it was the African Union that asked Senegal to try Mr. Habré “in the name of Africa.”

The court’s $11 million budget comes from donors, including the United States and France, the erstwhile Habré allies, and one-third is paid by the government of Chad, where President Idriss Déby has been in office for the 25 years since he overthrew Mr. Habré.

For Mr. Habré’s accusers, though, the trial’s taking place at all has been remarkable.

The former strongman had lived in exile in Senegal since 1990, and he was indicted there in 2000. Yet it took more than a decade of outside pressure before Mr. Habré was arrested.

Many atrocities that occurred during his years in power were already known, but the trial has uncovered new details about the scale and the workings of the repression as witnesses have dared to testify, even though some reported receiving death threats in Chad.