The JIC was then chaired by John Scarlett.
The JIC is at the heart of the British intelligence machinery.
The JIC has therefore concluded that there are no plausible alternative scenarios to regime responsibility.
"The JIC statement shows a level of certainty in the absence of physical evidence.
The JIC "thought that they had control of the substance and the content", Turnbull says.
The JIC, which prepares formal intelligence assessments, considered the scenario so unlikely that it did not estimate how long it might take.
The JIC report said video footage from the Damascus attacks was "consistent with use of a nerve agent, such as sarin".
The JIC, he told the the Royal Institute for International Affairs at the end of last year, had "stepped outside its traditional role..
The JIC is part of the cabinet office and personnel from MI5, MI6 and intelligence listening station GCHQ sit on the committee.
The JIC also "assessed that Iraq was likely to mount a terrorist attack only in response to military action and if the existence of the regime was threatened".
The JIC concluded that it was "highly likely" that Bashar al-Assad's regime was to blame, and that there are "no plausible alternatives to regime responsibility".
