>I would tend to believe Obama because he is much more credible than Putin, and has much more to lose if he can't produce evidence to support his claims.

>Despite Putin's call for transparency, the fact remains that he is unwilling to tell the truth about what happened.

You've made quite a jump to go from one sentence arguing that Obama is more credible than Putin to (indirectly) calling Putin a liar.

From what I've read, the following claims have been made by the Obama administration [1]:

1) Possess satellite imagery showing rockets firing from a location controlled by the Syrian army.

2) Transcripts of Syrian officials telling forces to ready gas masks.

3) Transcripts of Syrian officials discussing how to handle U.N. investigators inspecting the aftermath.

If the evidence is as clear as Obama is trying to make it appear, why not have an independent body from the U.N. review the evidence? Maybe this is already in the works, but I've seen no mention of it.

[1]http://seattletimes.com/html/politics/2021795842_apusuniteds...