BUENOS AIRES (Reuters) - Argentina sentenced 29 people, some with nicknames like “Blond Angel of Death” and “The Tiger,” to life sentences on Wednesday in a trial involving some 800 cases of kidnapping, torture and murder during the 1976-1983 dictatorship.

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Many defendants, including former Navy Captain Alfredo Astiz and Captain Jorge Acosta, were already serving life sentences for Dirty War crimes committed at the ESMA Naval Mechanics School that was converted into a clandestine prison and torture center.

For the first time in the so-called ESMA mega-case, however, Wednesday’s sentence included convictions for “death flights,” when people were drugged and their bodies dumped in the River Plate.

“Giving sedatives to our loved ones before or during the flight before throwing them in the river or the sea is unbelievable; it’s dismal,” said Lita Boitano, head of Relatives of the Disappeared and Detained for Political Reasons.

Boitano, who lost two children during the dictatorship, was among the hundreds of people gathered outside the federal courthouse in Buenos Aires listening to the convictions. They took more than three hours to read.

In addition to the life sentences, 19 people received jail terms of eight to 25 years. Six were cleared of wrongdoing, including Juan Alemann, a finance minister during the dictatorship and one of few civilians who had been accused of planning rights abuses.

Human rights groups estimate Argentina’s military government killed up to 30,000 people during the dictatorship. Most of their bodies were never found.

About 5,000 dissidents were held at the ESMA, and only about 200 people are known to have survived. Some of the initial 68 defendants died during the trial that started in 2012.

Astiz had been convicted in absentia in Europe of killing two French nuns held at the ESMA, which opened to the public as a human rights memorial in 2007.

Argentina has prosecuted many dictatorship-era crimes and last year convicted 15 ex-military officials of conspiring to kidnap and assassinate leftist dissidents as part of the Operation Condor program.

But a Supreme Court ruling earlier this year to decrease jail time for those convicted of human rights abuses spurred protests and stoked fears of backsliding.