Testimony from both medical personnel and information from casualties shows that rebels have been using Sarin gas. It is strong evidence but not proof. The attacks that have occurred have been blamed on both the regime and the rebels but the truth is still unknown.
New evidence highly suggests that Syrian government forces were responsible for chemical weapons attacks on August 21, 2013 in the Damascus suburbs. The attacks killed hundreds of civilians including several children. The chemical weaponry used is likely Sarin.
Syrian rebels, not the Assad Regime, may have made use of the deadly nerve agent, sarin, in their war-torn country. There is no confirmation and testing is still being preformed.