The problems with expert evidence

The Lucy Letby Case: Raising Questions About Expert Evidence in Medical Trials

The Lucy Letby case is the latest in a number of UK criminal medical cases that, beyond the rights and wrongs of each verdict, raise serious questions around how such cases are tried – especially when the evidence is limited, complex, and circumstantial.

The Importance of Expert Evidence

As an expert in the intersection of criminal and medical law, I am particularly concerned with how prosecution teams gather expert evidence in such cases – and how it is then communicated to juries through expert witnesses. Generally speaking, in complex medical cases, police and prosecutors may risk becoming overly reliant on a small pool of experts when dealing with highly technical issues beyond their expertise.

The Letby Case: A Challenge to Expert Evidence

In the Letby case, the prosecution’s selection and interpretation of evidence has now been challenged by an independent panel of 14 neonatal and paediatric experts. Letby is serving 15 whole-life prison terms after being convicted of murdering seven babies and attempting to kill another seven at the Countess of Chester hospital in north-west England. The chair of the panel, retired Canadian neonatologist Dr Shoo Lee, was co-author of a 1989 academic paper on air embolism in babies that was used in the prosecution’s case, but now says this evidence was misinterpreted by the prosecution.

The Risk of Cherry-Picking

In complex medical cases, I’m concerned that prosecutors – who may lack the medical expertise needed to fully grasp these complexities – may gravitate toward experts whose opinions align with a prosecutorial narrative, whether consciously or not. This can result in a narrowing of expert perspectives which might tend to focus only on those that bolster the case for conviction, while alternative views that could provide a more balanced assessment are excluded or marginalised.

The Need for a Medico-Legal Expert

I believe it’s in the interests of both parties, the defendant and the prosecution, that the jury fully understands the evidence presented in court. An impartial medico-legal expert could help ensure this understanding, without influencing the case’s outcome. Their role would be beneficial for clarity, helping both parties ensure the jury comprehends the complex evidence before them.

Appeals Process

One of the Letby appeal grounds involved an application to admit fresh evidence from Lee, challenging the conclusions reached from the 1989 study he co-authored. The court of appeal denied this, noting it did not meet the standards for fresh evidence. Refusals such as this highlights an essential aspect of public debate: the need for transparency about how the court of appeal evaluates new evidence, especially in cases that receive significant media attention.

Conclusion

While holding individuals accountable is essential, we must also shift our focus towards long-term, systemic reform. Only by addressing the root causes and strengthening oversight within healthcare institutions can we ensure that tragedies are never repeated. The criminal justice system, though necessary in cases of clear criminal conduct, should be complemented by proactive, preventative measures that foster a culture of safety, accountability and transparency in healthcare.

FAQs

• What is the Lucy Letby case?
  The Lucy Letby case is a high-profile criminal trial in the UK where a nurse was convicted of murdering seven babies and attempting to kill another seven at the Countess of Chester hospital in north-west England.
• What is the concern about expert evidence in medical trials?
  The concern is that prosecution teams may rely too heavily on a small pool of experts, potentially cherry-picking evidence that supports their narrative, while excluding alternative views that could provide a more balanced assessment.
• What is the proposed solution?
  The proposed solution is to introduce an impartial medico-legal expert to assist the jury in understanding complex medical evidence, without influencing the case’s outcome.