An Argentine court has begun the trial of an ex-police chief accused of murder during military rule, the first such case since an amnesty was scrapped.
Retired police chief Miguel Etchecolatz faces murder charges
Argentina's Supreme Court ruled last year that legal immunity for former officers was unconstitutional.
The judgement cleared the way for hundreds of officials to be tried for crimes during the 1976-83 dictatorship.
But rights groups say legal issues and institutional inertia have meant that only now has a case come to court.
The former director of investigations in the Buenos Aires police force, Miguel Etchecolatz, is accused of involvement in six murders, as well as torture and illegal arrest.
He was brought to court in La Plata, some 55km (35 miles) from Buenos Aires, early on Tuesday morning to avoid disturbances outside the court, Argentine media reported.
Etchecolatz, 76, is currently serving house arrest after being sentenced to 23 years on other charges, including crimes against humanity and stealing the baby of one of the victims of the military government.
He was the right-hand man of the feared head of the Buenos Aires police, the late General Ramon Camps.
One of his lawyers told the court that Etchecolatz had been following orders and acting in accordance with the legal situation prevalent in a state of war.
"I am not going to debate who was or wasn't right, that the judge will decide," the Argentine newspaper Clarin quoted lawyer Luis Eduardo Boffi Carri Perez as saying.
Dressed in a dark suit and holding a white rosary, the former police chief listened to the charges against him.
Between 10,000 and 30,000 people were killed or disappeared while the generals were in power between 1976 and 1983.
In the run-up to the return to civilian rule, the junta granted a blanket amnesty for all offences connected with the "Dirty War" as the widespread repression waged against left-wing opponents came to be known.
Argentina is slowly coming to terms with its recent past
The amnesty was highly controversial and was revoked and then reinstated.
The Supreme Court gave a final ruling last year that granting legal immunity to prosecution for ex-members of the security forces was unconstitutional.
Human rights groups and lawyers set about the task of trying to bring the surviving police and military men and their agents to justice. However, few trial dates have been set since the court's ruling.
"The justice system is slow to begin with and this is an unprecedented situation," Daniel Sabsay, a constitutional lawyer, told Reuters news agency.
Jorge Watts, who survived a clandestine detention centre during the dictatorship, told Reuters that time was on the defendants' side.
"The problem is that many repressors are dead, or some have lived to be tried but the witnesses are dead, and it is much more difficult to find proof after 30 years," Mr Watts said.
But for Jose Miguel Vivanco from Human Rights Watch, the first trial marks the "end of years of impunity".
Mr Etchecolatz's trial is expected to last at least three months, with more than 100 witnesses being called, including former presidents Maria Estela Isabel Martinez de Peron (1974-76) and Raul Alfonsin (1983-89).