The horrific events under a military dictatorship -- murders, kidnappings, torture, rapes, the abduction and sale of infants -- had gone unpunished for nearly 30 years.
But last year Argentina's Supreme Court overturned a pair of amnesty laws, and now the trials of military and police officials accused of human rights violations are finally under way.
In late June, the first trial, involving a police commissioner general named Miguel Etchecolatz, began here. With cameras rolling and winter light streaming through stained-glass windows in a belle epoque ballroom at City Hall, witness after witness has told how Etchecolatz and the forces under his command ordered, supervised and then covered up kidnappings and torture sessions.
Nora Formiga, for instance, was 27 years old when security forces abducted her and two friends from her apartment in November 1977. Her family was eventually told she had fled abroad, and it was only in 2002, shortly after her father died, that DNA tests proved that a body found in an unmarked grave here was hers.
"We don't have justice yet, but now we at least have the hope of it," one of her sisters, Maria Ruth Formiga, 67, said after testifying on Monday.
"It has been difficult to sit here and hear confirmed all the awful things our family had always supposed to be true, but this is the only way to make sure it never happens again," she said.
The trial is also bringing new evidence of previously unknown crimes to light. Testimony has revealed instances of prisoners giving birth to children whose names do not appear on existing lists of the disappeared, and in a recent inspection tour of a police station, investigators found hidden between bricks a 30-year-old register of prisoners illegally taken into custody.
"As the years have gone by, people have shaken off the fear they felt, even in the 1980s," after democracy was restored, said Estela de Carlotto, director of the Grandmothers of the Plaza de Mayo, a leading human rights group.
"As a result, the testimony we are hearing is more complete and detailed than ever," she said.
Etchecolatz was the main assistant to General Ramon Camps, the chief of the Buenos Aires provincial police in the first phase of the dictatorship that ruled Argentina from 1976 to 1983. In the 1980s Etchecolatz was sentenced to 23 years in prison for human rights violations during that period, but the conviction was nullified by the two amnesty laws passed later that decade.
In June last year, though, the Supreme Court declared that both measures -- known as the "full stop" and "due obedience" laws -- were unconstitutional, thereby making it possible to resume old prosecutions and begin new ones.
Camps had died by then, leaving Etchecolatz as the most senior surviving police official and most alluring target for prosecutors intent on using the trials to educate Argentine society, especially young people who did not live through or do not remember the dictatorship, about the evils of what happened here.
A second trial, that of a police official named Julio Simon, began shortly afterward and has already ended with his conviction and sentencing to 25 years in prison for a variety of offenses. But that trial, more limited in scope, has not had the same impact on the public because the judges declined to allow the proceedings to be filmed for broadcast on television.