Who is responsible for the use of chemical weapons in Syria

Preparations for a new military advance of the Syrian army on the rebels' positions accentuate greatly the issue of responsibility for earlier detected cases of chemical weapons use. There has been only confirmed fact of chemical warfare poisonous agents use in the region Khan al-Assal, north of Aleppo, dating 19 March. All the other evidence is based on the testimonies of the victims exclusively and the symptoms described don't match the ones with the injured in GB attacks.
The samples from Khan al-Assal made it possible to identify sarin and diisoprophylftor-phosphate. This information was released by the source in the chemical laboratory making tests ordered by the U.N. Commission investigating human rights abuses in Syria. The agents studied turned out to have been produced outside Syria and were all of small storing term due to lack of stabilizing additives in them. Furthermore, extraneous materials contained in them were identical to the ones collected in 2002 on the Canadian testing ground following the decompression of the sarin shell.
It was determined that a self-made unguided rocket had been used to carry GB agents, the rocket being blasted with hexogen. That shell couldn't be an authorized item In Syrian army arsenal. Its closest analogue is "Bashair-3" shell produced by Assad's opponents in Aleppo and Idlib provinces.
If it were the case involving the use of chemical weapons by government troops they would have employed the GB agents of Syrian make and authorized munition to ensure accuracy and safety of fire. The evidence got in wake of expertise exclude such a possibility.
The detention by Turkish security service of the Syrian fighters trying to deliver sarin load into Syria adds more meat to the experts' conclusions. According to mass media of Turkey, the guilty were released under the pressure of the western secret.
Reluctance of the USA and France to allow for the strongly forwarded by the U.N. Commission probe into the chemical weapons use in Syria resulted in the predictably unacceptable demands for Damask.
Now, experts have every ground for worry. Extremists may well employ their skills of handling GB agents to prepare new terrorist. Great Britain and France are said to be potential targets in the terrorists' hit list owing to their vigorous participation in special missions against Muslim countries and international terrorist organizations.