A Free Syrian Army fighter wearing a gas mask, carries his weapons as he walks past a damaged tank, after seizing a government military camp used by forces loyal to Syria's President Bashar al-Assad, near Idlib, June 13, 2013. Picture taken June 13, 2013. REUTERS/Abdalghne Karoof (SYRIA - Tags: CONFLICT) - RTX10NNC



The World's Marco Werman speaks with Hamish de Bretton-Gordon, a leading expert on chemical weapons, about the process of determining whether the Assad government in Syria has deployed them in its conflict with the rebels. Bretton-Gordon is a former commanding officer at the UK's Joint Chemical Biological Radiological & Nuclear Regiment. He explains that collecting that evidence is no simple matter.

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