UK says Russia's call for a joint investigation into the poisoning is "perverse"
As the Organisation for the Prohibition of Chemical Weapons begins investigations into the Skripal poisoning in The Hague, the United Kingdom has said Russia's call for a joint inquiry is perverse.
But chemical weapons expert Dr Ralph Trapp argues dialogue is crucial.
"It may look like an attempt to divert attention to a different kind of process," says Dr Trapp. "But I think it actually belongs to a discussion in the OPCW if there is an accusation that this was a chemical weapons use then there is an implicit accusation that there also has been an undeclared clandestine chemical weapons programme and that needs to be cleared up. "
"Perhaps more important today is what the results of the discussions in the executive council are going to be for the process that follows. What kind of mechanisms, what kind of discussions are going to be set up to resolve the issue rather than just try to play it out in the media and trying to come up with public accusations."
With accusations flying, Dr Trapp says science may not be able to provide certainty.
"The whole field of chemical forensics is fairly new, so we are still developing it," he says. "There are no universal databases that one can simply use and look at to find out what chemical signatures you can expect and it's a question of whether or not one has access to the actual materials in these labs or not."
The OPCW has taken samples from the site of the Salisbury attack and is expected to provide test results next week.