A new team to identify the perpetrators of chemical attacks in Syria is now "fully operational", the head of the Organisation for the Prohibition of Chemical Weapons (OPCW) announced last week. However, the creation of the Investigation and Identification Team (IIT) has already caused a rift within the OPCW and this looks set to continue if not worsen as work gets under way.

The decision to establish the IIT was taken at a special conference of the OPCW's member states last year, instigated by Britain. Russia and a small group of other countries opposed it and then, having failed to stop it, they sought to delay its implementation. Meanwhile the Syrian government – which denies ever using chemical weapons – says it doesn't recognise the IIT and won't cooperate with it.

Another OPCW body, the Fact-Finding Mission (FFM), has been investigating alleged chemical attacks in Syria since 2014 but its mandate prevents it from attributing blame – its role is limited to determining whether or not a chemical weapon was used. The basic idea behind the IIT is that it will pick up where the FFM's reports leave off and try to identify the "individuals or entities directly or indirectly involved".

The IIT's activities are confined to those cases where FFM reports concluded that a chemical weapon was used or was likely to have been used, and it has decided to focus initially on nine of them:

1. Al-Tamanah, 12 April 2014
2. Kafr-Zita, 18 April 2014
3. Al-Tamanah, 18 April 2014
4. Marea, 1 September 2015
5. Ltamenah, 24 March 2017
6. Ltamenah, 25 March 2017
7. Ltamenah, 30 March 2017
8. Saraqib, 4 February 2018
9. Douma, 7 April 2018

The OPCW says these were chosen after "taking into account the information gathered by the FFM, the number of casualties, the likelihood of retrieving additional information, and (when possible) the type of chemical detected".

One highly contentious case on the IIT's list is Douma, where a reported chemical attack on a rebel enclave in April last year led American, British and French forces to launch punitive airstrikes against the Assad regime. An investigation by the FFM later concluded there were "reasonable grounds" for believing a toxic chemical was used as a weapon, and said the toxic chemical involved contained reactive chlorine. Two gas cylinders found at the scene were fitted with tail fins suggesting they had been designed to be dropped from an aircraft, but Russia and Syria claim rebels planted the cylinders in order to implicate the regime.

In addition, the inclusion of Ltamenah on the list is likely to reopen old arguments about the use of sarin in Khan Sheikhoun in 2017 (which also resulted in US airstrikes). In Ltamenah, the FFM concluded that sarin was "very likely" to have been used on 24 March 2017 and "more than likely" on 30 March 2017.

The FFM also noted chemical "similarities" between the sarin samples from Ltamenah and those from an incident in Khan Sheikhoun a few days later. Its report listed the substances detected by lab tests in all three cases, but without further comment. The implication, though, was that whoever used sarin in Khan Sheikhoun also used it in Ltamenah.

Part of the IIT's brief, according to a report presented to the OPCW's Executive Council last week, is to look for "chemical markers that help identify the origin of the chemical used". On that basis it should be possible to determine whether the sarin came from Syrian government stockpiles or somewhere else.

Khan Sheikhoun itself is not on the IIT's list because it was the subject of a report by the UN/OPCW Joint Investigative Mechanism in 2017 which concluded that the Syrian government was responsible. Syria and Russia vehemently disagreed and shortly after the report was published Russia used its veto in the UN Security Council to shut down the Joint Investigative Mechanism – thus blocking further attempts to attribute blame.

In effect, the IIT is a replacement for the Joint Investigative Mechanism, but operating under the auspices of the OPCW rather than the Security Council. This means Russia can't veto it but can still try to obstruct its activities – as can others.

The political pressures faced by investigators in this type of work were described by Edmond Mulet when he was head of the now-defunct Joint Investigative Mechanism. "We find ourselves in a highly politicised environment," he said. "We do receive – unfortunately – direct and indirect messages all the time from many sides telling us how to do our work. And some of those messages are very clear in saying that if we don't do our work according to them – these different visions – then they will not accept the conclusions of our work."

The OPCW is clearly anticipating similar pressures in connection with the IIT – and trying to shield itself against them. Its report to last week's Executive Council meeting said:

"The IIT will conduct its operations in an independent, impartial, and objective manner, and shall refrain from seeking or obtaining instructions from any government or external source.

"Secretariat personnel serving within, or in support of, the IIT act in strict conformity with the OPCW Staff Regulations, Interim Staff Rules, and Code of Conduct and are required to sign a Secrecy Agreement with the OPCW.

"At all times, the IIT will ensure the security, integrity, preservation, and chain of custody of the information and material in its possession from the moment of receipt, collecting, analysing, and storing technical and scientific information meeting the highest technical standards, as well as the meticulous employment of forensic processes."

Last year the OPCW came under a series of cyber attacks, according to Director-General Fernando Arias, and it has since established a special fund to tighten up on "cyber security".

In April last year four Russian intelligence agents were caught in a car park adjacent to the OPCW's headquarters, attempting to hack into its wifi system. Later, foreign minister Sergei Lavrov broke OPCW rules by reading out parts of a confidential lab report at a news conference (and drawing the wrong conclusions from it).

More recently, an internal OPCW document marked “do not circulate” was leaked and posted on the internet.