Why Scientific Uncertainty Does Not Prevent Legal Conclusions

When it comes to civil claims, including clinical negligence cases, the court works on the balance of probabilities rather than the criminal standard of proof. A judge does not need scientific certainty in order to reach a conclusion, and the court must decide what is more likely than not based on the evidence available. 

But in medicine, we are trained to be cautious about causation, and I think this is one of the areas that can feel uncomfortable for medical practitioners when they first become involved in medico-legal work.

Medical training tends to reward caution. We are taught to differentiate correlation from causation, to avoid overstatement, and to recognise the limitations of evidence. In many situations, particularly where research is limited or conflicting, doctors and nurses become understandably hesitant about making definitive statements.

Courts approach uncertainty differently. In civil litigation, the standard of proof is not scientific certainty, it is the balance of probabilities. Put simply, the court asks what was more likely than not to have happened. That threshold is very different from the level of proof many clinicians instinctively look for before feeling comfortable drawing conclusions.

This difference becomes particularly interesting in aesthetic medicine, where evidence is not always as robust or straightforward as people assume.

Aesthetic practice evolves rapidly and new treatment trends emerge long before meaningful long-term scientific data exists. Not only do techniques change, but product use changes too and complication profiles continue to develop over time. And while some areas of practice are supported by strong evidence, others rely far more heavily on clinical experience, consensus opinion and observational data, which creates inevitable grey areas when complications occur.

As an Aesthetic Expert Witness, I sometimes see practitioners become uncomfortable discussing causation unless there is clear scientific literature directly proving a connection. Legally, however, the absence of definitive scientific proof does not necessarily prevent a court from reaching a conclusion on causation. That might feel counterintuitive from a medical perspective.

For example, in aesthetics, there are situations where patients develop symptoms or complications that do not fit neatly into established evidence pathways. Delayed inflammatory reactions following dermal filler treatment are one example. Psychological harm following cosmetic procedures can be another example. Questions also arise around filler migration, compounded treatments, online prescribing practices, or complications associated with treatments that have become popular faster than the evidence base has developed.

In some of these situations, the scientific literature may remain incomplete or evolving, and experts may disagree. Research may show association without definitively proving a mechanism, yet the court is still required to assess the evidence available and decide what is more likely than not.

That does not mean courts disregard science because expert evidence remains central to these cases. But the legal process recognises that uncertainty does not remove the need for decision-making.

Medicine does work within a framework of ongoing uncertainty because absolute certainty is relatively rare in many areas of healthcare, so most practitioners are comfortable acknowledging that limitations exist. But an expert witness may feel reluctant to state that a treatment probably caused a complication if the evidence falls short of definitive scientific certainty - although legally, “probably” is often precisely the question being asked.

The court is not asking whether causation has been established beyond all possible doubt, it is asking whether, having considered the evidence as a whole, one explanation is more likely than the alternatives.

I think aesthetic medicine presents particular challenges here because the industry still contains significant variability in standards, documentation, training and regulation. Many non-surgical treatments exist in a space between medicine and cosmetics, with procedures marketed heavily online. Patients may arrive with expectations shaped far more by social media than by clinical literature. Adding to that, complications may be underreported, follow-up inconsistent, and in some cases, continuity of care doesn’t exist.

One of the most important aspects of expert witness work is learning how to discuss probability honestly without drifting into speculation. There is a significant difference between saying something is merely possible and saying it is more likely than not. That distinction may appear subtle linguistically, but legally it is extremely important.

Experts must avoid overstating weak associations as established causation simply because a temporal link exists. Just because symptoms developed after a treatment does not automatically mean the treatment caused them.

Sometimes, the strongest medico-legal opinions aren’t absolute ones. They are the opinions that acknowledge uncertainty openly, explain the limitations of the evidence clearly, and still analyse what conclusions can reasonably be drawn despite those limitations.