The U.S. government insists it has the intelligence to prove it, but the American public has yet to see a single piece of concrete evidence — no satellite imagery, no transcripts of Syrian military communications — connecting the government of President Bashar Assad to the alleged chemical weapons attack last month that killed hundreds of people.
In the absence of such evidence, Damascus and its ally Russia have aggressively pushed another scenario: that rebels carried out the Aug. 21 chemical attack.
The early morning assault in a rebel-held Damascus suburb known as Ghouta was said to be the deadliest chemical weapons attack in Syria's 2½-year civil war. Survivors' accounts, photographs of many of the dead wrapped peacefully in white sheets and dozens of videos showing victims in spasms and gasping for breath shocked the world and moved President Barack Obama to call for action because the use of chemical weapons crossed the red line he had drawn a year earlier.
Yet one week after Secretary of State John Kerry outlined the case against Assad, Americans — at least those without access to classified reports — haven't seen a shred of his proof.
http://news.yahoo.com/lingering-doubts-over-syria-gas-attack-evidence-072755287.html