Existing Research

The first thing we should do is examine what research currently exists which tries to lay blame for the attack.
I will consider here only research which reaches a conclusion based on evidence, not general theories about what could have happened.
So far I'm aware of 3 serious analyses:

1. The US intelligence assessment, published August 30th, which assesses "with high confidence that the Syrian government carried out the chemical weapons attack against opposition elements".
2. The UN Report, which doesn't lay blame, but attempts to hint very heavily towards the Syrian Army.
3. The Brown Moses blog, and the Human Rights Watch report based on it, which analyzes public evidence related to munitions. They too point to the Syrian Army.

In the next posts I will try to analyze the quality of evidence and analysis in these reports. 

I also recommend reading the summary of conclusions.