The assessment that a "nerve agent" was used comes from multiple sources. Congress will receive the information, which is "classified." The clear implication is that we will not be able to review and evaluate the information.
Since the material is "classified," any debate or committee hearings on the evidence must be conducted in private . To do otherwise would risk the release of classified information.
Ruling out the rebels as a source of the attack
"We assess that the scenario in which the opposition executed the attack on August 21 is highly unlikely."
""the regime's preparations for this attack and its means of delivery, multiple streams of intelligence about the attack itself and its effect, our post-attack observations, and the differences between the capabilities of the regime and the opposition. "
"...the Syrian regime has used chemical weapons on a small scale against the opposition multiple times in the last year"
The government is blamed for the attack. In addition to the already referenced satellite images, the report implies that the rebels have not used chemical weapons and lack the ability to do so. But. is that so?
These claims ignore the reports of Carla del Ponte of the UH Human Rights Commission who said that rebel groups likely used chemical weapons, sarin gas specifically, in a March attack near Aleppo, Syria. If accurate, that implies that the rebels have delivery capabilities for chemical weapons.
Assessment opens up the consideration of motivation
"We assess that the regime's frustration with its inability to secure large portions of Damascus may have contributed to its decision to use chemical weapons on August 21."
This is, perhaps, the weakest point of the entire assessment. When you consider motivation, one question comes up immediately: Why would the Assad regime undertake a highly provocative attack using chemical weapons when a) the government was winning battles all over the country for the past two months and b) a UN weapons inspection team was already in Damascus to investigate past claims of chemical weapons use? The regime was preparing an attack on the rebel held areas of Damascus but it was hardly desperate. One could argue that the rebel groups were in a truly desperate situation - losing battles to the government on a regular basis and different rebel factions attaching each other.
Satellite imagery from the U.S. but not other sources
"Satellite detections corroborate that attacks from a regime-controlled area struck neighborhoods where the chemical attacks reportedly occurred."
We should see the imagery and also imagery from Russian satellites, which supposedly found just the opposite.
Crowd sourcing a collection of videos some of which may be fake
"We have identified one hundred videos attributed to the attack."
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