The Guardian newspaper said the Commission for International Justice and Accountability (CIJA) had already built three cases against the regime for crimes against humanity and is continuing to assemble evidence against others in the regime as well as in the opposition.
The British daily said the cases were largely based on government documents smuggled out of Syria by a team of 60 investigators who had risked their lives to collect the evidence that now runs to around half a million pages.
So far, the CIJA has compiled three cases against the regime based mostly on its bloody suppression of anti-government protests in 2011 that triggered the descent into civil war.
The first case centres on Assad and his war cabinet -- the Central Crisis Management Cell (CCMC).
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The third involves the security committee responsible for Deir Ezzor and Raqa provinces, and is based on smuggled documents detailing "how precise orders to crush the popular uprising flowed from Damascus to the governorates."
"The regime's mania for documenting orders as they travel down the chain of command -- and after-actions reports that flow back upwards -- has meant that the paper trail led unexpectedly to the very centre of power in Damascus," the paper wrote.
The documents provided insight into how the regime has organised itself during the war, revealing that the CCMC meets daily and minutes from the meeting are taken directly to Assad for review and notes that are then passed down the chain of command.
Despite compiling detailed evidence and receiving funding from several Western governments, CIJA staff acknowledged to the Guardian that for now there is no court to prosecute the cases they have compiled.