[42] Åke Sellström, the leader of the UN Mission, characterized government explanations of rebel chemical weapons acquisition as unconvincing, resting in part upon "poor theories".

[43] According to the Associated Press, "chemical and biological weapons experts have been relatively consistent in their analysis, saying only a military force with access to and knowledge of missile delivery systems and the sarin gas suspected in Ghouta could have carried out an attack capable of killing hundreds of people.

[75][87] On the day of the attack, George Sabra, the head of the Syrian National Council, said 1,300 people had been killed as shells loaded with poisonous gas rained down on the capital's eastern suburbs of Douma, Jobar, Zamalka, Arbeen and Ein Tarma.

[88] A spokesman for the Free Syrian Army's Supreme Military Council, Qassim Saadeddine, said, "people are growing desperate as they watch another round of political statements and UN meetings without any hope of action".

[99] On 18 August 2013, three days before the Ghouta attack, a UN mission headed by Åke Sellström[22] arrived in Damascus with permission from the Syrian government to investigate earlier alleged chemical weapons use.

[105] Later in the day the UN team came under sniper fire en route to Moadamiyah in western Ghouta (to the southwest of central Damascus), forcing them to return to their hotel and replace one of their vehicles before continuing their investigation four hours later.

[109] As a result of the delay caused by the sniper attack, the team's time in Moadamiyah was substantially shortened, with the scheduled expiry of the daily cease-fire leaving them around 90 minutes on the ground.

The report stated: "the environmental, chemical and medical samples we have collected provide clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used in Ein Tarma, Moadamiyah and Zamalka in the Ghouta area of Damascus.

[114] The report, which was "careful not to blame either side", said that during the mission's work in areas under rebel control, "individuals arrived carrying other suspected munitions indicating that such potential evidence is being moved and possibly manipulated".

[113] The inspectors wrote that they "collected clear and convincing evidence that chemical weapons were used also against civilians, including children, on a relatively large scale in the Ghouta area of Damascus on 21 August 2013".

[75] Deputy Foreign Minister Faisal Mekdad declared it a tactic by the rebels to turn around the civil war which he said "they were losing" and that, though the government had admitted to having stocks of chemical weapons, stated they would never be used "inside Syria".

[156][157][158] In April 2014 Hersh wrote an article, also published by the LRB, reporting that a former intelligence officer told him that the attacks were "covert action planned by Erdoğan's people to push Obama over the red line", speculating about Turkish government support for Al-Qaeda affiliate Al-Nusra Front's attempts to access sarin.

"[181] Doctors Without Borders also reported seeing a "large number of victims arriving with symptoms including convulsions, excessive saliva, pinpoint pupils, blurred vision and respiratory distress".

It summarised doctors' and paramedics' descriptions of the symptoms as "vomiting, foamy salivation, severe agitation, [pinpoint] pupils, redness of the eyes, dyspnea, neurological convulsions, respiratory and heart failure, blood out of the nose and mouth and, in some cases, hallucinations and memory loss".

"[5] Gwyn Winfield, editorial director at CBRNe World, analysed some videos from the day of the attack and wrote on the magazine's website: "It is difficult to define [an] agent by the signs and symptoms.

[190] According to analysis conducted in January 2014 by Theodore Postol and Richard Lloyd, of the Massachusetts Institute of Technology, the rockets used in the attack had a range of about two kilometers, which, the authors claimed, meant that the munitions could not have been fired from the 'heart' or from the Eastern edge of the Syrian Government Controlled Area shown in the Intelligence Map published by the White House on 30 August 2013.

"The other thing that seems inconsistent with sarin is that, given the footage of first responders treating victims without proper protective equipment, you would expect to see considerable secondary casualties from contamination – which does not appear to be evident."

"[204] Zanders however cautioned that these symptoms covered a range of neurotoxicants, including some available for civilian use as pest control agents, and said that until the UN reported its analysis of samples, "I can't make a judgement.

"[205] According to a report by The Daily Telegraph, "videos uploaded to YouTube by activists showed rows of motionless bodies and medics attending to patients apparently in the grip of seizures.

"[88] Hamish de Bretton-Gordon, a former commander of British Chemical and Biological counterterrorism forces,[206] told BBC that the images were very similar to previous incidents he had witnessed, although he could not verify the footage.

[3][82][215] An unnamed French government official said that the analysis was carried out by the Directorate-General for External Security (DGSE) and Direction du renseignement militaire (DRM) based on satellite and video images, on-the-ground sources, and samples collected from two April attacks.

[224] In a commentary published in The New York Times on 11 September 2013, Putin wrote that "there is every reason to believe [poison gas] was used not by the Syrian Army, but by opposition forces, to provoke intervention by their powerful foreign patrons".

The report blamed the chemical attacks on the Syrian government, saying rockets containing a nerve agent were fired from government-held territory into neighborhoods in the early morning, impacting at least 12 locations.

[196] The U.S. government assessment suggested a motive for the attack, describing it as "a desperate effort to push back rebels from several areas in the capital's densely packed eastern suburbs".

[236] Secretary of State John Kerry later announced that hair, blood, soil, and cloth samples collected from the attack sites had tested positive for sarin or its immediate breakdown products.

[151] Jeffrey Goldberg also reported that James Clapper, the Director of National Intelligence, personally told President Obama that the case for the Syrian government's responsibility was strong but not a "slam dunk".

However, Human Rights Watch argues that the Ghouta chemical attack was illegal under a different international agreement: Syria is a party to the 1925 Geneva Gas protocol, which bans the use in war of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices.

[253] After Russia and China blocked attempts to set up an international tribunal for Syria, survivors of the attack and human rights organizations have taken legal action in France, Germany, and Sweden.

[254][251] In February 2021, lawyers representing victims of the attack and two international human rights groups filed with judges at a special war crimes unit in France's palace of justice a complaint regarding the Syrian government's use of chemical weapons.

United States Holocaust Memorial Museum marked the ninth anniversary of Ghouta chemical attack, describing the event as "a new nadir" in the list of horrific atrocities of Bashar al-Assad.