Most likely scenario

If you combine:

1. "New York Times Puts Launch Point of Chem Weapons Rockets Inside Rebel Contested Area";
2. "INSIGHT - military intervention in Syria, post withdrawal status of forces" ("They dont believe air intervention would happen unless there was enough media attention on a massacre, like the Ghadafi move against Benghazi. They think the US would have a high tolerance for killings as long as it doesn't reach that very public stage."); and
3. "Britain’s Daily Mail: U.S. ‘backed plan to launch chemical weapon attack on Syria”" ("It is our understanding that the Daily Mail report was removed following a libel suit launched by Britam Defense and Intelligence against the Daily Mail") and "Deleted Daily Mail Online Article: “US Backed Plan for Chemical Weapon Attack in Syria to Be Blamed on Assad”"

you could be forgiven for coming to the conclusion that by far the most likely scenario for the chemical attack in Syria - if in fact there was a chemical attack - is an American-British false-flag operation run by the British using Ukrainian mercenary chemical weapons experts.