UN report does not prove responsibility for use of chemical attack in Syria

The only thing this report does prove is that a chemical weapon, Sarin Gas, was used by person/persons unknown.

Conclusions

27. On the basis of the evidence obtained during our investigation of the Ghouta incident,
the conclusion is that, on 21 August 2013, chemical weapons have been used in the ongoing
conflict between the parties in the Syrian Arab Republic, also against civilians, including
children, on a relatively large scale.

The report may be read here in PDF format.  http://www.cnn.com/interactive/2013/08/world/syria-documents/index.html?hpt=hp_t2

The information concerning the recovered munitions on page 21 is somewhat interesting.  If one wants to rush to judgment and accuse then look no further than the Cyrillic engraving on the bottom of the engine.