Given the horrific events unfolding in Syria, it is understandable that there are calls for something to be done in response to what John Kerry has rightly condemned as a "moral obscenity". Yet in circumstances where our knowledge is incomplete about what happened, who was responsible and how best to respond given the complexity of the conflict that has engulfed Syria, there is a need to exercise caution and precaution.

This requires avoiding recourse to policy based on a false dichotomy between what Tony Blair recently described as "commentary or action". Policy choices are being implicitly framed as a well-defined crossroads, when the evidence about what transpired and what action to take is not. Instead, we need what Obama described as a more "informed decision" about which policy pathways should be taken.

According to the emerging western narrative, on 21 August a large scale attack using neurotoxic chemical weapons was launched on targets in Ghouta, a suburb of Damascus, by forces of the Assad regime. There is little doubt that something horrific has happened. However, we do not have a credible "chain of custody" from sampling to analysis (as could be provided by UN inspectors working with the WHO and OPCW), and it is difficult to determine the exact nature of the agent or agents used or what exactly transpired.

Adding to the complexity, acquiring such information is not easy. As Meselson has stated, "obtaining reliable chemical analyses is not nearly as simple as non-specialists might think" (pdf). Yet without either "some kind of smoking gun" or details on the circumstances of the chemicals' release, the truth about what happened is highly uncertain.

It is certainly possible that the Assad regime has employed chemical weapons, but the timing of the attack, occurring so shortly after the arrival of inspectors, so close to where they are currently operating and when the regime is winning in the two-year conflict, raises questions. As such, is it entirely reasonable to discount the possibility, raised by Carla Del Ponte of the UNHCR in relation to earlier allegations, that "the rebels have used chemical weapons"?

While this possibility sits uncomfortably with the western narrative on the Syrian conflict, and may well turn out to be mistaken, uncritically accepting the prevailing account of events in Ghouta ignores the extent to which the history of chemical (and biological) warfare is riddled with false allegations, misinformation and propaganda which, as Robinson has pointed out, have often been deftly exploited by "well-intentioned as well as unscrupulous people to vilify enemies and to calumniate rivals" (pdf).

Uncritical and therefore unscientific acceptance of a particularly framing of events also undermines the UN inspectors' efforts to conduct independent, on-site, fact-finding activities about what happened that can feed into more informed and transparent future action. The existing uncertainty means it is not just difficult to formulate an evidence-based solution, "it is irrational even to try, let alone claim, this".

The provision of more objective evidence would provide the international community with a better basis to pursue future legal action. Without it, we are dealing with wild western, rather than western justice. Someone within the territory of the regime – if not the regime itself – has committed a serious violation of the laws and customs applicable in international armed conflict (pdf). Under the circumstances, they could thus be liable to prosecution by the International Criminal Court.

The alternative, limited military options available to western governments (including most probably "a single punitive attack" involving multiple missile strikes) are subject to risk, uncertainty, ambiguity and ignorance (pdf). Under such conditions a legal approach, which is much more suited to dealing with uncertainty than military strikes, is likely to be a more fruitful and safer course of action in the longer term.

The history of allegations of chemical weapons' use is largely the history of misinformation and disinformation. This makes it much more difficult to work out what has happened in a legitimate and transparent way. Given the risks, uncertainties, ambiguities and ignorance attached to all the available policy options, a response of caution, precaution and transparency is called for.

This will doubtless be unpopular among many, certainly based on the impassioned comments appended to several articles on this issue. Yet as terrible as the use of chemical weapons is, terrifying actions have taken place against civilians on a daily basis during this two-year humanitarian catastrophe, and have generated only a limited response.

Given the risks of western involvement in yet another war in the Middle East, caution is required to allow UN inspectors the time to gather the necessary evidence and generate the technical information needed for a law enforcement option to emerge. Over-hasty reactions, well intended as they may be, are actions without the benefit of evidence. Such actions are unscientific, hubristic and rarely end well.

James Revill is a research fellow with the Harvard Sussex Program at SPRU, which researches public policy on issues involving biological and chemical weapons. The views are not necessarily those of HSP or SPRU