For eight years, Suleymane Guengueng and a handful of other former political prisoners in this impoverished country carefully gathered and hid evidence of mass murder and torture ordered by a U.S.-backed dictator, waiting for the day they could face their tormentors in court.

They may finally get their opportunity. In court cases unprecedented in Africa, Chadians are pursuing the brutal former dictator, Hissene Habre, and his collaborators, many of whom still hold powerful positions. Human rights activists say the legal action was inspired by the campaign to prosecute former Chilean dictator Augusto Pinochet.

"These cases sound an alarm for dictators across the continent," said Reed Brody, advocacy director for New York-based Human Rights Watch, which has supported the suits. "They know their impunity can be questioned. First Pinochet, then Habre, and they know maybe they could be next. It shows accountability is actually possible."

U.S. officials have said that Washington provided hundreds of millions of dollars to Habre and helped train his intelligence service, whose members are now accused of torture.

In February, Guengueng and four others got a court in Senegal--where Habre has lived in luxurious exile since 1990--to indict him for torture. Habre's lawyers acknowledged that rights violations took place under his rule but said Habre did not order them and the statute of limitations had expired.

In another precedent, more than 50 Chadians have filed cases here in the past month against their alleged torturers, including some of Habre's closest collaborators. Almost as surprising as the filing is that the cases have not been thrown out, human rights workers and diplomats said.

Guengueng, a 48-year-old former civil servant, wears thick glasses because the beatings he received in prison in the 1980s damaged his eyesight. He sat with other former prisoners in a tiny office off a dusty road here that houses the Chadian Association of Victims of Political Repression and Crime and spoke in a near whisper about his 28 months in clandestine prisons around the capital.

Scores of prisoners died of asphyxiation and heat exhaustion, and guards often left the bodies in the crowded cells for two or three days to decompose quickly in the heat. The most notorious prison, according to Guengueng and other victims, was La Piscine, a one-time swimming pool covered with a concrete roof, near the U.S. aid mission.

Habre's security guards routinely tied up prisoners and forced their mouths over exhaust pipes of cars whose engines were running. Or, Guengueng and the others recalled, they beat prisoners or administered electric shocks. Guards would pour water over the men once a day, forcing them to lick it off their bodies or the floor to keep from dying of thirst.

A decade or more later, the hardest thing for the former prisoners is seeing their torturers as members of the government security forces. "They still mock us," Guengueng said. "If you give a torturer work, you are still violating human rights."

With help from the United States and France, Habre ruled this mostly desert nation of 7 million from 1982, when he won a bloody battle with rival warlords, until 1990, when he was overthrown by his erstwhile ally, Idriss Deby, the current president. During those years, Chadian and international human rights investigators say, the Directorate of Documentation and Security (DDS), which was controlled directly by Habre, killed at least 40,000 civilians and imprisoned and tortured hundreds of thousands of others.

In a land that has known little government and much war since its titular independence from France in 1960, Habre rose to power because the United States and France sought his help in opposing his northern neighbor, Libyan leader Moammar Gaddafi. Because Habre was willing to fight Libya, which the Reagan administration regarded as a dangerous Soviet puppet and a sponsor of international terrorism, the United States backed his rebel movement with millions of dollars in weaponry, despite widespread evidence that Habre had carried out extensive massacres, according to U.S. officials familiar with the covert program.

The aid to Habre was the first clandestine operation launched by Reagan's CIA chief, William J. Casey, when he took over the agency in 1981. The covert aid, channeled through Sudan and Egypt, eventually totaled hundreds of millions of dollars, the U.S. officials said.

After Habre seized power, he immediately set up the DDS with French and U.S. help, according to published accounts and U.S. sources. Its officers quickly established a reputation for brutality, but still received U.S. training in intelligence analysis. Habre's intelligence units and the CIA shared information extensively, according to three former senior U.S. officials familiar with events at the time.

"The CIA was so deeply involved in bringing Habre to power I can't conceive they didn't know what was going on," said Donald Norland, U.S. ambassador to Chad from 1979 to 1981, who knew Habre well and urged the CIA and State Department to back off in their strong support for the warlord. "But there was no debate on the policy and virtually no discussion of the wisdom of doing what we did."

In addition to the covert aid, U.S. economic and military assistance--$182 million worth during Habre's rule--flowed to Chad, where average annual income is about $200 and 80 percent of the people live by subsistance farming.

In the summer of 1983, when Libya invaded northern Chad and threatened to topple Habre, France sent 3,000 paratroops with air support, while the Reagan administration provided two AWACS electronic surveillance planes to coordinate air cover. By 1987 Gaddafi's forces had retreated, abandoning an estimated $1 billion in Soviet-supplied weaponry.

Because of this Cold War victory, the United States and France ignored Habre's increasingly ruthless one-party rule. "Habre was a remarkably able man with a brilliant sense of how to play the outside world," a former senior U.S. official said. "He was also a bloodthirsty tyrant and torturer. It is fair to say we knew who and what he was and chose to turn a blind eye."

But when Deby, Habre's former chief of staff, rebelled in 1990, the Cold War had faded, and neither France nor the United States moved to save Habre.

After taking power, Deby ordered a commission of respected jurists to investigate the human rights abuses of the Habre years. The commission reviewed documents left by Habre's government, interviewed hundreds of witnesses and survivors, and exhumed mass graves. It documented 4,000 killings, which it said amounted to less than one-tenth of the crimes committed.

Despite severely limited time and resources, the panel produced a book in May 1992 that described a "veritable genocide against the Chadian people." It published names and photographs of DDS agents responsible for the worst abuses and documented how, in 1990, Habre emptied the national treasury before fleeing.

"Among all the oppressive institutions of the Habre regime, the DDS distinguished itself by it cruelty and contempt for human life," the book said, illustrating the point with photos of piles of human skeletons unearthed from the agency's killing fields.

"The DDS was responsible to the office of the presidency because of the confidential nature of its activities," the book said. "There were no intermediaries between the DDS and Hissene Habre."

But, according to a Human Rights Watch report, "With many ranking officials of the Deby government, including Deby himself, involved in Habre's crimes, the new government did not pursue" the commission's findings. Almost immediately after the commission's book was published, the Deby government locked away the commission's files, and it kept many of the DDS agents identified as torturers or killers in its new security force.

While N'Djamena's press reprinted parts of the commission's report, it had little impact because fewer than 30 percent of Chadians can read and the newspapers do not circulate beyond the capital. The report was virtually ignored by the outside world.

Guengueng and other victims had quietly gathered dossiers on 792 killings by the DDS, hoping to use the evidence to prosecute Habre. But when Deby's government buried the commission's report and rehired Habre's torturers, Guengueng said they realized the dossiers were dangerous. They buried the files in scattered places for safekeeping.

"What the victims did was remarkable," said Brody, of Human Rights Watch. "When we came along this year to help investigate, we found they had a treasure trove of information."

What caused the shift was the Pinochet case, which brought recognition under international law that human rights violators could be prosecuted anywhere, said Delphine Djiraibe, president of the Chadian Association for the Promotion and Defense of Human Rights. She helped Guengueng and four others build their case against Habre in Senegal. On Feb. 3, in an unprecedented action, the former president was arrested and indicted on charges of torture.

That case stalled under Senegal's newly elected president, Abdoulaye Wade. In April, Wade appointed Habre's main attorney as his special legal adviser, and in June, the president abruptly moved the chief investigating judge, who had indicted Habre, off the case. In July the torture charges were dismissed on grounds that Senegal was not the proper venue.

"This is the most important human rights case in Senegal's history, and we are behaving like a banana republic," said Alioune Tine of the Dakar-based African Assembly for the Defense of Human Rights. "Sacking and promoting judges in the middle of a sensitive case are shenanigans unworthy of Senegal's democracy." The dismissal is under appeal.

In Chad, Deby has promised a shift in policy as Habre's victims have become more politically active and international attention to the case has grown. He met with the victims' association for the first time on Sept. 27 and told them "the time for justice has come." He promised to fire all former DDS officials and reopen the commission's files.

"We are going step by step," said Ismael Hachim, president of the victims' association. "We have a person filing a case against every person we know who tortured. We say let justice do its work. That is what we want. But who can repair all that evil?"