Two pieces in regards to the "proof" that Assad was the source of the Sarin gas use in Syria:
1)
Story Leak reports the following:
The German magazine Focus and The Guardian are reporting that the majority of the information indicating dictator Bashir Assad’s use of poisonous gas comes from the 8200 unit of the Israeli Defense Forces.
The 8200 unit is Israel’s equivalent of the National Security Agency; it intercepts and collects electronic intelligence. The evidence the unit collected apparently consists of a recording of two Syrian officials talking about the use of poisonous gas. There appears to be no physical evidence that the poisonous gas actually exists, yet US officials are discussing the possibility of an imminent attack on Syria. An attack that, as Anthony Gucciardi has warned us, could really be all about entering a ‘hot’ scenario with Russia and other nations who support Assad.
Of course one may not feel that Story Leak is a reputable source, so we can go to their source material,
The Guardian
The 8200 unit of the Israeli Defence Forces, which specialises in electronic surveillance, intercepted a conversation between Syrian officials regarding the use of chemical weapons, an unnamed former Mossad official told Focus. The content of the conversation was relayed to the US, the ex-official said.
2) A report from
Mint Press
However, from numerous interviews with doctors, Ghouta residents, rebel fighters and their families, a different picture emerges. Many believe that certain rebels received chemical weapons via the Saudi intelligence chief, Prince Bandar bin Sultan, and were responsible for carrying out the dealing gas attack.
“My son came to me two weeks ago asking what I thought the weapons were that he had been asked to carry,” said Abu Abdel-Moneim, the father of a rebel fighting to unseat Assad, who lives in Ghouta.
Abdel-Moneim said his son and 12 other rebels were killed inside of a tunnel used to store weapons provided by a Saudi militant, known as Abu Ayesha, who was leading a fighting battalion. The father described the weapons as having a “tube-like structure” while others were like a “huge gas bottle.”
Take that with however amounts of salt you want but I believe this account. It supports a theory I've had that the rebels had these items and they were detonated when the government forces attacked their position which made it
look like the Syrian government had deployed the weapons. Unlike the claims of the administration, we know the rebel groups have Al-Qaeda elements in them. We know Al-Qaeda is not beyond killing civilians to further it's aims.
Remember that the US and Israel have a deep interest in going after Syria as it sees that as a way of getting at Hezbollah and Iran. And remember the entire Libya campaign.