If Barry Big-Ears had evidence that Assad was responsible for use of Chemical weapons, he and the rest of his gang wouldn't be wasting our time with John F'n Kommie's "stirring" oratory on what a poopyhead Assad is, or three to five pounds of qualifiers for every fact-based sentence he reads off the Tely-Prompter.
They have no evidence that it's Assad, the sources they're quoting are Muslim Brotherhood sources, and it's becoming increasingly plain that chemical weapons ARE being used.
So, if it isn't Assad's fingerprints on the button, who does that leave?