SÃO PAULO, Brazil – A court in São Paulo has overturned the convictions of 74 members of the Brazilian Military Police implicated in the 1992 Carandiru prison massacre that left 111 dead, the latest twist in a case that languished for years and exposed problems in the Brazilian legal system and a lack of human rights.

In 2013 amd 2014, the trial of the officers at the Fórum Criminal Monsenhor Mário Guimarães produced the convictions at the hands of several different juries and subsequent sentences in what was the largest mass trial in Brazilian history.

Fast forward to the present, however, and another wrench has been thrown in the trial that took over a decade to begin with: the 4th Criminal Court of the São Paulo Tribunal of Justice has granted a request to the defense lawyers of the 74 officers that effectively annuls their convictions.

Ivan Sartori, the judge who made the decision to reverse the convictions, accepted the defendants’ legal team’s claims that the violent actions undertaken by their clients were were not intention but acts of “legitimate self-defense.”

This was a notion that was rejected by five different juries during the previous court sessions that resulted in convictions.

Sartori explained that his decision was rooted in the fact that 74 of 77 officers were convicted, which meant that 3 of the officers were acquitted.

“The judiciary powers cannot deliver two results for the same situation in the sense that some are convicted and others are acquitted. As such, there is no other way to go forward but to extend the acquittal to the other accused individuals,” Sartori said in a strange, rambling explanation.

Furthermore, Sartori said that “some members of the jury did not know what they were doing” and that “they were confused,” referring to the 35 different people that served as the jury; 7 different jurors oversaw 5 different cases.

Finally, Sartori said that given high number of officers and prisoners involved, the forensic investigation could not find exactly which officer killed which inmate. This was one of the tactics employed by the officers, who were accused of heavily tampering with evidence and not allowing forensic experts into the prison until they were “ready,” but this was apparently not taken into consideration by the judge.

“The fact that 111 prisoners can be killed without anybody being held responsible after 24 years is not only shocking, but sends a terrifying message about the state of human rights in Brazil,” said Atila Roque, Director at Amnesty International Brazil.

“Carandiru illustrates everything that is wrong with Brazil’s prison system and with the country’s lack of justice for human rights violations committed in the context of public security operations,” Roque continued.

“Unless serious steps are taken to improve prison conditions and ensure all those responsible for human rights violations face justice, we will inevitably see this tragedy repeated across the country for years to come,” he concluded.

The massacre itself took place on October 2, 1992, after inmates in South America’s largest prison, the Casa de Detenção Carandiru de São Paulo, or Carandiru Detention Center of São Paulo, were involved in a fight during a football game.

Soon enough, however, the fight turned into a full-fledged prisoner revolt due to the prisoners’ objections to the sub-human conditions within its walls. Without negotiating first and without any hostages being taken by the prisoners, the Military Police were called in and they stormed Hall 9 of the sprawling compound.

According to survivor accounts, the officers indiscriminately began firing at any prisoner who crossed their path, even those who were just hiding in their cells or visibly surrendering.

The overcrowded prison, which was built to hold a capacity of 3,300 but housed nearly 7,300 on that day, turned into a slaughterhouse: within a span of no more than 20 minutes, 111 inmates were killed by the security forces who fired over 500 rounds collectively. Each inmate was shot 5 times on average during the killings.

Of those killed, 102 died from gunshot wounds while the remaining nine died from injuries inflicted by other weapons. Many of those killed had gunshot wounds in the back of their heads from bullets that were fired at short range, execution-style. Most of the victims were found naked, covered in blood and some even had their hands tied as seen in disturbing, graphic images taken shortly after the massacre.

The brutality continued throughout the levels of the prison as the military police ascended the floors of the building; 15 were killed on the first floor, 78 on the second, 8 on the third and 10 on the fourth floor. The subsequent trials themselves were divided into cases by the floors of the prison.

None of the armed officers were killed or seriously injured and none of them were struck by weapons fire, a piece of evidence that negated the officers’ claims that inmates had weapons or that they had taken them from the officers.

Hall 9, which housed some 2,100 prisoners and specifically where the massacre took place, was the area of the prison that housed new arrivals, many of whom had no previous criminal record prior to their jailing. Indeed, the majority of the massacre victims were young men and 89 of the 111 that were killed were never convicted but still awaiting trial for the crimes of which they were accused.

The very first trial concerning the Carandiru massacre began in 2001 with only one defendant: Colonel Ubiratan Guimarães, the then-head of the Military Police of the State of São Paulo. A unit of that security force was the group of officers that stormed Carandiru, led by Guimarães, who would be rushed out during the raid after being injured by an exploding gas canister.

Guimarães was charged with the murders of the prisoners and he was convicted and sentenced to 632 years in prison. After a lengthy appeals process, however, he was cleared after the court accepted his argument that he was only following orders from above. The Governor of São Paulo at the time, Luiz Antônio Fleury Filho, always insisted that neither he or anyone in his government ordered military police to enter the prison.

Guimarães was never officially arrested for his role in the massacre despite standing trial nor was he ever imprisoned.

After retiring from the Military Police of the State of São Paulo with 34 years with the department under his belt, he turned to politics and served in the Legislative Assembly of São Paulo State as a substitute representative.

He was a hardline advocate of harsher punishments for prisoners during his time in office, and pushed for the ban on conjugal visits and prison furloughs. In his re-election campaign in 2002, he even used the political number 14111, with the last three numbers (that the candidate gets to choose) matching the number of prisoners killed in the massacre, but he said that ‘111’ was the number of the horse he rode while training in the Military Police’s Cavalry.

In September of 2006, seven months after his conviction was overturned, the man who always claimed to have a “clear conscience” was gunned down in his apartment in an upscale area of São Paulo. He bled to death at the age of 63 from a gunshot wound to the abdomen. His murder, which had the markings of a very well-planned and executed hit, has never been solved.

Finally, In the phases of the trials that lasted throughout 2013 and 2014, over 21 years after the massacre, the officers involved were put on trial. When the trial wrapped, 74 officers were convicted and sentenced to prison terms ranging from 48 to 624 years, or more than 21,000 years in prison in total.

As was the case with Guimarães, however, none of the convicted officers served any prison time as the defense lawyers immediately lodged an appeal. The eventual overturn of the decision in the case was another painful development for human rights groups in Brazil that say police extrajudicially kill thousands of people in the nation every year with impunity.

Now that the court has overturned the convictions and sentences, the prosecution team is now preparing an appeal of their own in which they hope for another reversal or at the least, a re-trial.

As for Carandiru itself, it was finally torn down in December of 2002 after standing for 82 years. It was demolished and replaced with the Youth Park Complex. The complex is comprised of a large public park, technological and arts schools, a city library and a memorial space to the massacre victims called the Espaço Memória do Carandiru.