Former Argentine President Carlos Menem has missed the opening day of his trial over a huge bomb attack against a Jewish centre in Buenos Aires in 1994.
Mr Menem, 85, said he could not attend because of health reasons.
He is one of 13 people accused of obstructing the investigations. He has repeatedly rejected the allegations.
The attack against the Amia Jewish Cultural Centre in the heart of the Argentine capital killed 85 people and injured more than 300.
Argentine prosecutors say it was planned and financed by Iran, and carried out by Hezbollah, the Lebanese Shia Islamist movement.
The Iranian government has always denied any involvement.
The trial is expected to last at least a year. More than 100 witnesses will be heard.
Mr Menem’s former intelligence chief Hugo Anzorreguy also missed the trial citing health reasons.
He was sentenced to seven years in jail in 2013 for his role in a scheme to smuggle weapons and ammunitions to Ecuador and Croatia.
But he has avoided serving time in jail because of his age and because of his immunity as a senator for La Rioja province.
‘Code of silence’
Relatives of the victims say there is a culture of impunity and intimidation in Argentina that have hampered the investigations.
“Argentine society is waiting for a response based on the real truth, while those that are here today did everything to prevent that,” said Sergio Burstein, head of an association of survivors of the attack.
“It will be difficult to break the code of silence,” he told the Reuters news agency.
Earlier this year, special prosecutor Alberto Nisman appeared dead in his flat in Buenos Aires the day before he was due to appear in court.
He had accused President Cristina Fernandez de Kirchner of covering up Iranian involvement on the Jewish centre attack.
But in March an Argentine appeals court has upheld a decision to dismiss the case against Ms Fernandez.
She always denied the allegations.