The case has raised questions about the church's role during Argentina's so-called Dirty War and although Von Wernich is the first priest to face trial for crimes, about 20 others are alleged to have worked with the military government.

"Von Wernich would visit prisoners after horrific torture sessions and asked them to trust him, to give him information in exchange for an improvement in the conditions of their detention," Carlos Zaidman, a survivor of one of the detention camps, said.

The prosecution said, in a statement read to the court, that: "Von Wernich participated assiduously and maintained direct contacts with the detainees" and was fully complicit in the crimes committed by the state.

'Disappeared'

The trial was attended by dozens of relatives of victims of the military government, including members of the Mothers of the Plaza de Mayo group whose children are among the 30,000 people who "disappeared".

About 200 protesters outside the court could be heard shouting "assassin" as the trial got under way.

"Von Wernich would visit prisoners after horrific torture sessions and asked them to trust him, to give him information"

Carlos Zaidman, torture survivor
The government has pledged to guarantee the safety of the 126 witnesses expected to give evidence, among them a Roman Catholic bishop and Adolfo Perez Esquivel, a sculptor and human rights advocate who was awarded the Nobel peace prize in 1980.

Last year, during the trial of a former police investigator on genocide charges, the chief prosecution witness, a torture survivor called Jorge Julio Lopez, disappeared and is still missing.

"It must be clear that the Church is not on trial, but that the role played by its hierarchy during the dictatorship will be shown," Guadalupe Godoy, a lawyer representing some of the victims, said.

After Argentina returned to civilian rule in 1983, Von Wernich moved to a small parish 250km from Buenos Aires before heading to Chile where he worked as a priest under a false name.
  
He was extradited to Argentina and arrested in 2003 after amnesty laws passed at the end of the dictatorship were declared unconstitutional.