Everything Assad and Putin have said has been lies.
They both said that Assad had no chemical weapons.
They both said that chemical weapons had not been used.
They both said that it was the rebels that used chemical weapons when all the evidence says Assad was the culprit.
So the evidence is that they are not to be trusted in any way.
More evidence of this:
Report: Assad scattering chemical weapons to 50 sites - Israel News, Ynetnews
Report: Assad scattering chemical weapons to 50 sites
American officials say US, Israeli intelligence agencies still believe they know where most of Assad regime's chemical weapons are located, but with less confidence
Ynet
Published: 09.13.13, 08:01 / Israel News
A secretive Syrian military unit at the center of the Assad regime's chemical weapons program has been moving stocks of poison gases and munitions to as many as 50 sites to make them harder for the US to track, The Wall Street Journal reported Friday, citing American and Middle Eastern officials.
The American newspaper quoted officials as saying the movements of chemical weapons by Syria's elite Unit 450 could complicate any US bombing campaign in Syria over its alleged chemical attacks,. It also raises questions about implementation of a Russian proposal that calls for the regime to surrender control of its stockpile, they said........more