Certainty on Trial: What the Expert Witnesses Could and Could Not Prove at the Sturgess Inquiry

Public inquiries into deaths involving chemical weapons rarely lack expert witnesses. The Sturgess Inquiry is no exception. Its record has been shaped by toxicologists, chemical-weapons specialists and intelligence analysts whose evidence translated complex science into a form the public could follow. But the value of that evidence did not lie in its technical density. It lay in whether the inquiry could test it, qualify it and explain its limits.

That is the central tension in any case where scientific authority meets legal scrutiny. An expert can describe what a laboratory result suggests, what a clinical picture is consistent with, or what an intelligence assessment concludes. An expert cannot decide the ultimate question of accountability. The Sturgess Inquiry's expert evidence therefore needs to be read not as a verdict delivered by scientists, but as a body of testimony that had to survive cross-examination, disclosure and public reasoning.

The authority of the expert

Expert witnesses occupy an unusual position in a courtroom or inquiry room. They are there because they know more than the tribunal about a specialised subject, yet they cannot determine the facts. Their authority depends on method, transparency and a willingness to acknowledge uncertainty. Where that authority is overstated, it can crowd out the legal questions that matter.

In the Sturgess proceedings, expert evidence helped explain the nature of Novichok, the circumstances of exposure and the likely consequences. It also had to be tested against alternative explanations. Counsel for the inquiry and representatives of interested parties were entitled to ask not simply whether an expert was credible, but whether the underlying assumptions were sound. That distinction is important. A witness can be honest and still be wrong. A method can be reputable and still have limits. The inquiry's task was to make those limits visible.

Toxicology and the limits of inference

Toxicological evidence is often treated as if it speaks with a single voice. In reality, it speaks in probabilities. It can address dose, route, timing and clinical effects. It may support a conclusion that exposure to a particular substance occurred, but it cannot always establish source, intention or the precise mechanism by which a person came into contact with it.

That does not diminish toxicology. It defines its role. In the Sturgess Inquiry, toxicological testimony provided a framework for understanding how a chemical agent could affect the body and what the clinical evidence might mean. Cross-examination probed whether those conclusions rested on established science or on inference. The difference matters in a public inquiry because inference can be a bridge too far when it is presented as certainty.

The lesson is not that experts should be treated with suspicion. It is that their evidence should be presented with its confidence levels intact. A possibility, a probability and a conclusion are not interchangeable. When technical evidence carries the weight of public accountability, the inquiry record must show where the science ends and judgement begins.

Chemical weapons analysis and the problem of provenance

Chemical-weapons experts can speak to the identity of a substance, its likely purity, its synthesis and its relationship to known programmes. They cannot, on scientific evidence alone, establish political responsibility. Attribution involves intelligence, history and judgement. That is a different kind of claim, and it must be tested differently.

The Sturgess Inquiry's chemical-weapons evidence therefore had to be read carefully. Experts could explain what the presence of Novichok indicated about capability and provenance. They could discuss the significance of particular compounds or methods. But the move from technical finding to state responsibility required more than laboratory analysis. It required an assessment of intelligence, sources and context.

That is why cross-examination was so important. It asked whether an expert had stayed within the boundaries of their discipline. It asked whether a conclusion was based on evidence available to the inquiry or on assumptions imported from elsewhere. In cases involving state actors, those questions are not legal technicalities. They go to the heart of public trust.

Intelligence analysts and the open record

Intelligence evidence presents a different challenge. Analysts work with material that may not be fully disclosable. Sources must be protected. Methods may be sensitive. Yet a public inquiry cannot simply accept an assessment because it comes from an authoritative body. It must find a way to test the assessment without destroying the conditions that made it possible.

Where intelligence assessments formed part of the Sturgess picture, the inquiry had to balance secrecy against scrutiny. Closed material procedures can protect legitimate interests, but they also limit what the public can see and what representatives can challenge. The result may be lawful and necessary, yet still leave a gap in public understanding. That gap is not automatically a scandal. It is a cost, and it should be acknowledged.

The best response is procedural rigour. The inquiry should explain what could not be disclosed, why, and what safeguards were used. It should ensure that the substance of intelligence evidence is tested as far as possible in open session. And it should avoid presenting an intelligence assessment as though it were a laboratory result. They are different forms of knowledge, with different strengths and weaknesses.

Cross-examination as quality control

Cross-examination is not peer review. It can be theatrical, repetitive and aggressive. But it performs a function that no expert report can perform on its own. It tests consistency. It exposes assumptions. It asks what an expert would expect to see if a different account were true. In an inquiry involving technical evidence, that function is essential.

The Sturgess Inquiry's record shows the value of experts who can distinguish between what their discipline supports and what it does not. An expert who concedes a limit is more useful than one who defends every inference. The public does not need scientists to sound certain. It needs them to be clear about the basis of their conclusions and the conditions under which those conclusions might change.

What this means for future cases

Several lessons emerge for future inquiries where expert evidence carries the weight of public accountability. First, experts should state confidence levels in plain language. Second, methods and limitations should be disclosed early, not extracted under pressure. Third, public summaries should separate findings from inferences and explain the difference. Fourth, closed material should be accompanied by robust safeguards and clear explanations. Fifth, no inquiry should treat expert consensus as a substitute for evidence about state responsibility.

The Sturgess Inquiry will be judged in part by whether its expert evidence helped the public understand what happened and what could not be proved. That is a higher standard than technical competence. It requires scientific authority to be placed under legal scrutiny without being either inflated or dismissed. Certainty is rarely absolute. The public interest lies in making that clear.