CAIRO — Some 55,000 photographs smuggled by a defected Syrian soldier provide "clear evidence" of "systematic torture and killing" of 11,000 detainees by the government, a team of senior war crimes lawyers said.
Three former prosecutors at the tribunals for the former Yugoslavia and Sierra Leone examined the pictures and files provided by a former member of Syria's military police.
They said the pictures showed evidence of crimes against humanity and war crimes by the regime of President Bashar al-Assad.
The report was released ahead of the Geneva II peace conference, which aims at finding a political solution for Syria's nearly three-year conflict.
According to the pro-opposition Syrian Observatory for Human Rights, at least 130,000 people have been killed in the civil war. The UN put the toll at 100,000 in July, and has stopped counting.
The graphic images in the latest report show men with strangulation marks, brutal beatings, signs of electrocution as well as starvation.
The lawyers said that photographs showed that a numbering system was used by the Syrian government to identify both the detainees and the branch of the security service responsible for their detention and death.
The documentation, which the lawyers said was evidence of organized killing, was used to keep track of those killed in order to inform their families, who would be told that they died either of a heart attack or respiratory problems.
"The need to photograph those who were killed is a strong pointer to the fact that the killings were systematic, ordered, and directed from above," according to the inquiry team.
The majority of victims were young men most likely between 20 and 40 years old. The forensics team examined some 5,500 of the photos.
The lawyers said the former soldier, identified as Caesar in the report, revealed no signs of being "sensational," nor did he seem partisan.
"Although he was a supporter of those who opposed the present regime, the inquiry team is satisfied that he gave an honest account of his experiences," according to the report.
"In fact, he made it quite plain that he never witnessed a single execution. There were many other reasons which drove the inquiry team to its conclusion that his evidence was reliable and could safely be acted upon in any subsequent judicial proceedings."
He said he sometimes photographed up to 50 bodies a day.
He told the lawyers that sometimes the place "looked like a slaughterhouse."
One of the three lawyers who authored the report, Sir Desmond de Silva, the former chief prosecutor of the Special Court for Sierra Leone, likened the images to those of Holocaust survivors.
The emaciated bodies were the product of starvation as a method of torture, "reminiscent of the pictures of those [who] were found still alive in the Nazi death camps after World War II," he said in a CNN interview.
The lawyers told CNN that they were hired to write the report by the British law firm Carter-Ruck, which was funded by government of Qatar, a strong supporter of the rebels fighting to oust al-Assad.
The United Nations and rights groups have previously said that mass executions and unlawful killings by both sides of the conflict may amount to war crimes.
Throughout the civil war in Syria, which started with anti-government protests in March 2011, al-Assad's regime has denied accusations of human rights violations and blamed "terrorists" for the violence.
In January last year, the UN High Commissioner for Human Rights, Navi Pillay, asked the United Nations Security Council to refer alleged war crimes and crimes against humanity committed in Syria for investigation by the International Criminal Court at The Hague.