Unlike countries such as Argentina and Uruguay, Brazil has never prosecuted anyone for human-rights offenses carried out during its military dictatorship, which lasted from 1964 to 1985.

This is due to a 1979 amnesty law, which let sleeping dogs lie. And perhaps also because while Brazil’s military rulers were responsible for the torture and execution of dissidents, it was on a relatively small scale: Some 400 disappeared or killed is the widely used figure, compared with tens of thousands in Argentina.

But the wheel may be beginning to turn. In April, violence broke out between police and demonstrators in Rio de Janeiro at an event commemorating the 1964 military coup. Weeks later, Human Rights Watch commended federal prosecutors for bringing kidnapping charges against Carlos Alberto Brilhante Ustra, a retired army colonel.

And on May 16, in Brasilia, President Dilma Rousseff formally inaugurated a "truth commission" to examine human-rights violations committed from 1946 to 1988, with a focus on the dictatorship.

In the late 1960s and early '70s, much of the state’s brutality was aimed at repressing left-wing revolutionaries. And as everyone in Brazil knows, Rousseff herself participated in the guerrilla movement and was imprisoned and tortured, though there's no proof that she took part in armed actions.

“We are not moved by revenge, hatred or the desire to rewrite history,” Rousseff said. Instead, she said, the motivation was simply to find the truth. In a sign of how important this commission was to her personally, the president cried during her address. Four ex-presidents were also in attendance, including Luiz Inacio Lula da Silva and Fernando Henrique Cardoso. Still, military top brass sat stony-faced in the audience and pointedly did not applaud.

The Folha de Sao Paulo newspaper suggested 10 unpunished crimes that the commission should investigate, including the 61 guerrillas killed in a conflict in Araguaia from 1972 to 1974, whose bodies were never found; the suspected murder of politician Rubens Paiva; and the notorious case of journalist Vladimir Herzog, who the regime said hanged himself in prison, but who is believed to have been tortured and killed.

But the commission won't have the power to bring criminal charges. Its very creation, which took two years,  apparently involved complex negotiations with both sides. And its members are already arguing with each other. One is the lawyer Rosa Cardoso, who defended Rousseff during the dictatorship era. Cardoso said the commission wouldn't examine crimes committed by the left-wing resistance. These included armed bank robberies, kidnappings and killings. The leftists argue that these acts were punished by the regime at the time, often by torture and murder.

Jose Carlos Dias, another commission member and a former justice minister, publicly contradicted Cardoso and said everything would be analyzed, including crimes by the left.

This concerned Marcelo Semer, a Sao Paulo writer and judge, who criticized the idea on his blog on Terra magazine:

The false discourse of balance and equality that has been preceding its installation flashes a red light … It propagates the erroneous ideas that to do justice is to investigate 'the mistakes of both sides,' as if there were two groups that clashed freely in a civil war. Resistance to the truth commission is the son of the torturous and cynical reasoning that always tried, in vain, to legitimize the coup, the allegation that the military immersed us in two decades of one dictatorship just to save us from another.

There is talk of a list of more than 100 crimes by the armed resistance being circulated by "militares.'' And the prospect of the resistance being investigated raises an interesting possibility. One of its most famous crimes was an armed robbery in 1969 by the VAR-Palmares guerrilla group, in which a safe of money was stolen from the Rio de Janeiro mansion of the famously corrupt former Sao Paulo Governor Adhemar de Barros's lover.

On opening the safe, the gang found much more than they had expected: about $2 million in U.S. currency. The story of how much of the money was later squandered, stolen or simply lost is told in the book "O Cofre do Dr. Rui'' by journalist Tom Cardoso. He alleges that some of the dollars were changed into Brazilian currency by the gang's most famous member -- Dilma Rousseff -- and another comrade, posing as foreign tourists at the Hotel Copacabana.

This suggests, intriguingly, that the president of Brazil may at some point be charged with laundering the proceeds of an armed robbery. At the very least, it might cause her some embarrassment, wrote columnist Raymundo Costa in the business daily Valor:

"The story of the robbery of Adhemar de Barros's safe will certainly return to the debate, which is now public. The intention of the more radical military is to embarrass the president of the Republic, who was part of the VAR-Palmares, responsible for the 'expropriation' action, in the jargon of the left."

In a piece for the Observador Politico, columnist Jose Barata pointed out that that the creation of the commission had come not long after a poll showing the popularity of Brazil's armed forces was at historically high levels. He wondered in whose interest it was to raise doubts about the institution that enjoyed the highest public confidence. “Truth commission? Which one?” Barata asked. “In whose hands will it become effective?"

Nobody asked the bigger questions: To what extent was the use of violence against a dictatorship that imprisoned, tortured and killed its citizens justified? How can a truth commission hope to balance what both sides want? Whose truth, exactly, does it intend to investigate? At present, it seems nobody knows.

(Dom Phillips is the Rio de Janeiro correspondent for World View. The opinions expressed are his own.)

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To contact the writer of this blog post: Dom Phillips at domphillips23@gmail.com.

To contact the editor responsible for this blog post: Timothy Lavin at tlavin1@bloomberg.net.