Argentina's former president Carlos Menem went on trial along with 12 co-accused, charged with obstructing the investigation into the 1994 bombing of a Jewish centre in Buenos Aires which killed 85 people.
The unsolved bombing recaptured the headlines this year when the prosecutor leading the investigation, Alberto Nisman, died.
Menem, 85, was President from 1989 to 1999 and is now a senator.
He was absent from the federal criminal court in Buenos Aires as the trial got under way, with his lawyer claiming he was unable to attend because of health problems.
Menem has already been convicted in a separate case of trafficking arms to Croatia and Ecuador, but has never served his seven-year sentence thanks to his immunity as a senator.
In the current case, the former president is charged with ordering judge Juan Jose Galeano, who is also on trial, to drop the so-called "Syrian trail", which led investigators to suspect late Syrian president Hafez al-Assad of involvement in the bombing plot.
During the initial probe, investigators believed Mr Assad may have ordered the bombing to take revenge on Menem for reneging on a promise to sell Argentine-manufactured arms to Syria.
Judge Galeano is accused of paying Carlos Telleldin, who supplied the pickup truck used in the bombing, a $400,000 bribe to falsely accuse 10 police officers of involvement in the bombing.
The initial investigation, which Judge Galeano oversaw from 1994 to 2003, resulted in a trial that was thrown out halfway through in 2004 on grounds of serious procedural violations.
All those accused were acquitted, including the police officers.
The investigation was then assigned to Nisman, the late prosecutor, who concluded the attack was in fact carried out by the Lebanese Shiite group Hezbollah on orders from Iran - a claim Tehran denies.
In 2007, Nisman ordered arrest warrants for former Iranian president Akbar Hashemi Rafsanjani and other high-ranking Iranian officials.
In 2013, Argentina and Iran reached a deal for the suspects to instead be investigated by a joint commission.
Nisman alleged the deal was a conspiracy between the Iranians and members of current Argentine President Cristina Kirchner's government.
Last January he filed a report accusing Ms Kirchner of protecting the Iranian suspects in exchange for oil and trade benefits.
He was due to present his findings to Congress when he was found dead in his bathroom after being shot in the head on 18 January 2015.
The investigation into his death is ongoing.
His case against Ms Kirchner has since been thrown out for lack of evidence, a decision upheld by two appeals courts.
