An ex-navy captain dubbed the Blond Angel of Death has gone on trial in Argentina with 18 others for kidnap and torture during military rule.
Alfredo Astiz and the other defendants are accused of abuses at the Navy Mechanics School detention centre.
He is accused of involvement in the disappearance of dozens of people, including two French nuns.
Between 10,000 and 30,000 people are believed to have been disappeared during the 1976 to 1983 dictatorship.
Mr Astiz is alleged to have had a central role in the abduction and disappearance of the nuns, Alice Domon and Leonie Duquet, investigative journalist Rodolfo Walsh and several founders of a human rights group, the Mothers of the Plaza de Mayo.
He is said to have helped security forces by infiltrating meetings of the Mothers at a church in Buenos Aires.
Leonie Duquet was thrown from a plane during one of the many "flights of death" during which the military disposed of prisoners.
Her body was washed ashore and she was buried in an unmarked grave, until her remains were formally identified in 2005. Alice Domon's remains have never been found.
Mr Astiz denies any knowledge of such flights and argues that he was following orders to protect Argentina from extremist violence.
The Argentine courts have identified 250 navy personnel who worked in the Navy Mechanics school at the time - some 70 have been charged so far.