The head of the commission, Brazilian diplomat and scholar Paulo Sergio Pinheiro, told the UN's top human rights body that the government's killing of civilians often through the use of ubiquitous checkpoints exceeds the crimes against civilians perpetrated by the militants and other anti-government armed groups.
The Islamic State extremists and anti-government armed groups are not "the sole agents of death and destruction inside Syria," Pinheiro told the 47-nation Human Rights Council in Geneva.
"The Syrian government remains responsible for the majority of the civilian casualties, killing and maiming scores of civilians daily both from a distance using shelling and aerial bombardment and up close, at its checkpoints and in its interrogation rooms," Pinheiro said.
"Checkpoints are often the starting point of a horrific journey of disappearance, torture, sexual abuse and, for many, death. Checkpoints are used to enforce sieges and to trap civilians in areas under indiscriminate bombardment."
Pinheiro expressed the commission's deep frustration that the international community has not found a political solution to end Syria's civil war, which has killed over 190,000 people.
"We have charted the descent of the conflict into the madness where it now resides. ... But we have been faced with inaction," he said.