Oh there will be evidence, you cant deliver that stuff and not have the delivery vehicles left behind - they dont go bang for the most part. So we'll probably have some shells. Of course they'll be able to say what it was - sarin etc. They can also establish what type of capability was needed to deliver it, whether it was actually delivered in that manner (as opposed to being placed there and detonated) and general telemetry data if it was.
So they can say on the balance of probabilities that the SAA have the capability and the evidence points to them firing it. But unless they have the guy who ordered it and the guy who loaded it and the guy who pulled the switch, you can never be 100% sure.
Waiting for 100% sure is a mugs game. Its like we dont prosecute anyone for murder unless they admit it. throw in the politics around the UN, the various influences and manipulations, the drafts for review and approval, the jobs on the line and the favours to cut...
WMDs are the new napalm apparently... not that the SAA didnt already use napalm on a kids schools yesterday, ok its the new napalm +.
Go away troll.