Three top security officers working under Syrian President Bashar Al Assad are facing charges of crimes against humanity and war crimes over the deaths of two Frenchmen.
They allegedly tortured and killed a French father and son who were arrested in Syria as anti-government protests swept the country in 2011, sparking war.
About 50 activists gathered near Paris Criminal Court in France, chanting for freedom and in support of the hundreds of thousands who have died or disappeared in Syria's war.
Ali Mamlouk, former head of the National Security Bureau, Jamil Hassan, former director of the Air Force intelligence service, and Abdel Salam Mahmoud, former head of investigations for the service in Damascus, will be tried in absentia.
Paris Criminal Court is hearing cases against them and their alleged role in the deaths of Mazzen Dabbagh and his son Patrick.
"For the first time, French courts will address the crimes of the Syrian authorities and will try the most senior members of the authorities to ever be prosecuted since the outbreak of the Syrian revolution in March 2011," the International Federation for Human Rights (FIDH) said.
The Dabbagh family lawyer Clemence Bectarte hailed "the culmination of a long legal battle".
“This trial represents immense hope for all Syrian victims who cannot attain justice,” she said. "Impunity continues to reign in Syria, so this trial aims to bring justice to the family and echo the stories of hundreds of thousands of Syrian victims."
Trials into abuse in Syria have taken place elsewhere in Europe but in those cases the accused held lower ranks.
The current trial began after seven years of investigations by a French judicial war crimes unit.
At the time of his arrest, Patrick Dabbagh was a 20-year-old arts and humanities student at the University of Damascus. His father was a senior education adviser at the French School in Damascus.
They were arrested in November 2013 by men who claimed to belong to the Syrian Air Force intelligence service.
"Witness testimony confirms that Mazzen and Patrick were taken to a detention centre at Mezzeh military airport, which is run by Syrian Air Force Intelligence and notorious for the use of brutal torture," FIDH said. adding the pair were not involved in anti-government protests.
Investigating judges said it was "sufficiently established" that the two men "like thousands of detainees of the Air Force intelligence suffered torture of such intensity that they died".
French investigators and the Commission for International Justice and Accountability collected accounts from dozens of witnesses of torture and mistreatment at Mezzeh Prison, including the use of electric shocks and sexual violence.
During the hearing, researcher Ziad Majed said the Syrian prison system was the "backbone of the regime".
“The three defendants are part of the Al Assad system. I know their names; they are also famous in Lebanon,” he said, suggesting they are well-known for being part of the Assad government.
After his two-hour testimony, he joined the demonstrators, calling for justice for the disappeared.
Author and Syrian expert Garance Le Caisne also testified. “Torture is not to make people talk but to silence them," he said. "The regime is very structured. Arrests are arbitrary. You disappear. You can go buy bread or meat and not return home."
The father and son were declared dead in 2018. The family were formally notified that Patrick died on January 21, 2014 and Mazzen on November 25, 2017.
In 2016, Mazzen Dabbagh's wife and daughter were evicted from their house in Damascus, which had been requisitioned. The prosecution said those acts were "likely to constitute war crimes, extortion and concealment of extortion".
If the three accused are convicted, they could be sentenced to life in prison in France. The verdict is expected on Friday.
