Every public housing complex in America is filled with individual tales of struggle and survival. This is the story of a dapper man in a black fedora who lives in unit 16G in the Bronx.

His name is Souleymane Guengueng, and he brought down a murderous African dictator.

In the 1980s, Mr. Guengueng was one of numerous people imprisoned and tortured during the brutal reign of President Hissène Habré in Chad, a landlocked country in central Africa. When he was released from prison after two and a half years, Mr. Guengueng began a quest for justice, meticulously recording the testimonies of survivors and the relatives of those who had been killed at the direction of Mr. Habré. He wound up with records detailing the abuse and murder of more than 700 people.

Human rights advocates collected his accounts and used them as critical pieces of evidence to pursue criminal action against Mr. Habré. The legal case was not an easy one. Finding a court to prosecute a head of state proved difficult. For more than 16 years, the case bounced between nations and continents, with Mr. Guengueng offering his personal plea for justice to anyone who would listen.

In May, in Dakar, Senegal, where Mr. Habré had lived in exile, the dictator was finally convicted. Next week, a court there will hear his appeal.