Three senior Syrian officials will face trial in absentia in a Paris court on Tuesday accused of involvement in the disappearance and subsequent death of a French-Syrian father and his son.

It is the first time that a serving Syrian official will go on trial for alleged war crimes.

The long-running case revolves around the disappearance and subsequent death of father Mazen Dabbagh and his son Patrick, who were arrested by Syrian Airforce Intelligence agents in Syria in November 2013 and later died in custody.

One of the officers accused of complicity in their disappearance and torture - Ali Mamlouk - is still in the Syrian security apparatus, as a security adviser to President Bashar al-Assad.

The two others - Jamil Hassan and Abdel Salam Mahmoud - are a former director and director of investigation at the Airforce Intelligence unit.

None of the three accused will attend the trial in the Cour d’Assises, which is scheduled to last four days.

The Syrian Information Ministry did not immediately respond to a request for comment about the case.

Syria’s government, Assad, and ally Russia have rejected accusations of mass killings and torture in a war that the United Nations has said claimed hundreds of thousands of lives.

Mazen Darwish, head of the Syrian Centre for Media and Freedom of Expression, which is supporting the case, said it was the first to try a serving Syrian official.

He said it would be significant to all Syrians as it pertained to “arbitrary detentions, torture (and) extrajudicial killings,” which he described as “systemic behavior by the regime.”

There are no efforts to prosecute members of the Syrian government at home in Syria, where critics say the courts serve the president’s interests. Previous trials in Europe have targeted former officials.

There has been no accountability yet in international tribunals either, as Syria is not a member of the International Criminal Court.

However, the International Court of Justice has ordered Syria to halt torture.