(CNN) -- Human rights activists decried Tuesday a Haitian judge's decision not to try former dictator Jean-Claude "Baby Doc" Duvalier for human rights violations.
The United Nations Office of the High Commissioner for Human Rights said Duvalier must be prosecuted for alleged crimes that include torture, rape and extrajudicial killings.
"The high commissioner has consistently reminded Haiti of its absolute obligation to investigate these well-documented serious human rights violations and to prosecute those responsible for them," spokesman Rupert Colville said.
Human Rights Watch echoed those concerns in what it called the most important criminal case in Haitian history.
"This ruling is another reminder that Haiti's justice system has almost always been on the side of the powerful, no matter how gruesome or destructive their crimes," said Reed Brody, special counsel for the organization. "We hope that it will be overturned on appeal."
Haiti, said Brody, "has an obligation to its people to investigate and prosecute the grave violations of human rights under Duvalier's rule."
The investigative magistrate overseeing the case, Carves Jean, ruled that Duvalier will face trial on corruption charges stemming from his 15 years in rule but not for human rights abuses, the Haitian Press Agency reported.
Jean said the statute of limitations had run out on those alleged crimes.
Duvalier, who called himself "president for life," fled Haiti in 1985. He stunned the world by returning from 25 years of exile in France to his homeland a year ago.
Within days of his return to Port-au-Prince, he was charged with human rights crimes as well as financial wrongdoing: He allegedly embezzled hundreds of millions of dollars on which he lived in exile. As such, the statute of limitations has not run out on those allegations.
Human Rights Watch and Amnesty International have documented what they call systematic violations under Duvalier's rule. Both organizations accuse Duvalier of imprisoning and torturing hundreds of Haitians, including journalists, and using violent means to silence voices of opposition.
Amnesty gave the public prosecutor in the Duvalier case 100 documents that it said detailed cases of human rights violations.
"The cases of human rights abuses we documented in Haiti are likely to be only a small proportion of what really happened during Duvalier's rule," Javier Zuniga, a special adviser at Amnesty International, said last year. "We will probably never know the true extent of the horror, but carrying out effective investigations will go a long way towards delivering justice."
Amnesty International's documents told the experiences of cobblers, taxi drivers, filmmakers, mechanics, distillers and even hairdressers, all of whom, they say, were arrested for anti-government activity.
Human Rights Watch said the statute of limitations ruling contravenes the decisions of the Inter-American Court of Human Rights, by whose judgments Haiti is legally bound.
The United Nations human rights office, which had offered technical assistance to Haitian authorities to bring the case to trial, said it was deeply disappointed.
"It is clear under international law that there is no statute of limitations for such crimes, and the U.N. human rights office has provided technical assistance and legal advice stressing this point," Colville said.
"We urge the relevant authorities to ensure that justice is, belatedly, delivered to the many victims of human rights abuses committed under the government of Mr. Duvalier. There can be no true reconciliation and forgiveness without justice."