Source: The Conversation – UK – By Amel Alghrani, Professor of Law, University of Liverpool
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. These cases often rely heavily on expert witnesses, whose testimony is crucial yet can be open to interpretation.
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. This dependence can inadvertently lead to “cherry-picking” – selectively presenting evidence that supports a particular narrative, while overlooking alternative perspectives that could provide a more comprehensive or balanced view.
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.
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.
In trials where juries hear only a limited number of expert voices, there’s a risk they may not receive a sufficiently balanced understanding of the case. In addition, rare diagnoses may lack the robust scientific literature typically needed to validate medical opinions in court.
Medical experts, like professionals in any field, can have differing opinions, especially in cases involving judgment calls or grey areas in medical practice. Without exposure to a range of viewpoints, jurors may miss alternative interpretations of the same evidence, which could be crucial for fair deliberation.
Of course, the defence also has the opportunity to call its own experts, potentially offering counter-arguments to prosecution evidence. But decisions by a defence team not to call certain experts may be based on legal strategy, resource constraints, or concerns about how the testimony will withstand cross-examination. When this happens, it can amplify the weight of the prosecution’s selected experts, potentially skewing the jury’s understanding.
Jurors naturally place a high level of trust in experts, assuming their testimony is both accurate and confined to their area of expertise. So, when experts venture beyond their remit, jurors may accept these statements uncritically, unaware that such testimony may lack the depth required in such complex medical cases. This issue is particularly concerning in circumstantial prosecutions where the case often hinges more on expert interpretation than on direct evidence, increasing the risk of misunderstanding or misjudgment.
Expert overreach
Testimony from experts unfamiliar with the practical pressures of certain clinical settings may lead to distorted interpretations of what a “reasonable” course of action would have been under the circumstances. This can result in unfair judgments, particularly when the nuances of clinical decision-making aren’t fully explored.
Experts also sometimes “overreach” their duties in court, offering opinions that extend beyond their remit. In the case of surgeon David Sellu, who was jailed for gross negligence manslaughter in November 2013 before being freed three years later, having spent 15 months in prison, the court of appeal noted that expert witnesses had repeatedly expressed opinions on whether Sellu’s conduct amounted to gross negligence – an assessment the court said should have been left to the jury.
In that case, the experts directly addressed the “ultimate issue” of whether Sellu’s actions were grossly negligent. But that was for the jury to decide, not the experts, and I believe the trial judge should have intervened. A key change needed by the UK legal system, in my view, is to establish clearer guidelines to ensure experts do not exceed their role – whether in a complex financial fraud or criminal medical trial.
Incidentally, while the judge in the Sellu trial didn’t give the jury correct direction (this was a key finding by the court of appeal that made the conviction unsafe), I don’t think it was entirely the judge’s fault. The law surrounding gross negligence manslaughter, particularly when applied to doctors unintentionally causing a patient’s death, is fraught with ambiguity. The lack of clear guidelines on what constitutes “gross” negligence, coupled with inconsistent application of the law, has sparked widespread concerns about its fairness and appropriateness in the medical context..
Make-up of a jury
Letby’s trial also highlights the limitations of the current jury system in such complex medical cases. The original trial was one of the longest in UK legal history, lasting ten months. The idea of jury trials is you’re tried by your peers, but if you’re a healthcare professional, you’re arguably not really being tried by your peers.
In England, jury service is compulsory and jurors are chosen randomly from the electoral register, but there are some exemptions and deferrals available in specific circumstances, such as serious illness, disability, or full-time caregiving. Additionally, people can apply for deferral if serving would cause significant hardship due to work commitments, including shift work or conflicts with important public duties. This is particularly relevant for professionals who cannot easily take extended time away from their roles.
This adds to the question of whether a jury, composed of 12 lay people with no specialised medical knowledge, can effectively assess intricate, often conflicting medical evidence. As Rebecca Helm highlights in her book How Juries Work (2024), while expert testimony aims to enhance jury understanding of complex evidence, jurors often lack the necessary background knowledge to fully grasp or critically assess it. This can lead to challenges in properly weighing competing expert opinions, especially in adversarial systems where experts present differing views.
In the Letby case, the vast amount of medical evidence presented for each baby likely made it challenging for a lay jury to fully comprehend. Additionally, they may have felt intimidated or hesitant to ask the judge questions, further complicating their ability to critically engage with the evidence.
Of course, it’s important to understand the backdrop for cases like this. I’m very aware of how overstretched, understaffed and under-resourced our hospitals are. And in the Letby case, we know that severely premature babies who are born on the cusp of viability often have a lot of comorbidities. It’s vital that jurors have a clear understanding of such specific context – which is outside the normal experience of most of us – when they come to make their decisions.
The jury’s role is to assess expert evidence independently, yet this can be difficult without clear guidance. In the Sellu trial, the absence of a “route to verdict” document was another significant issue. While not always mandatory, such a document is often used in complex cases to help jurors separate medical facts from legal conclusions.
Without it, the jury was left without clear guidance, increasing the risk of confusion and misapplication of the law. While the court of appeal did not say a route to verdict was strictly required, it strongly indicated that its omission contributed to an unfair trial process.
Expert advisors for juries
In complex criminal cases, like fraud or medical trials, where a large amount of expert evidence is presented, it can be challenging for lay jurors to fully understand and assess the evidence. Elsewhere in Europe – including in Italy, Spain and France – expert judges or advisers are often involved in complex cases to help guide the jury and clarify professional standards relevant to the case.
Given the complexity of cases like Sellu and Letby, it’s worth considering whether jury reform is needed in the UK to ensure fair trials. A potential solution is the inclusion of an expert, such as a medico-legal advisor, who can assist juries in understanding and weighing medical evidence. This would provide clarity on complex issues and help jurors navigate the case more effectively. It would be a practical, cost-effective step that maintains the integrity of jury trials, while addressing challenges specific to complex medical manslaughter and murder cases.
This medico-legal expert would serve solely to assist the jury in understanding complex issues presented during the trial, and would have no role in the deliberation or decision-making process. They are separate to the judge who oversees the trial, and their precise expertise would be dependent on the particular nature of the case.
Of course, everything would have to be confidential in accordance with jury rules – their introduction would simply be to facilitate decision-making and explain complex matters to the jury.
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.
Further, it may also be worth considering specialist medical juries for certain complex criminal cases, such as the Letby trial, where the evidence is highly technical. The sheer volume of complex medical information presented for each baby in this case suggests that a jury without specialised medical knowledge could struggle to fully grasp the evidence.
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.
While it remains to be seen whether the court grants a new appeal for Letby, after the criminal cases review commission reviews the latest evidence provided by Lee’s panel, the Thirlwall inquiry has been sitting since September 2023, looking at events at the Countess of Chester Hospital on the basis that Letby is guilty. It will ultimately make recommendations about different aspects of this wider medical ecosystem, but it’s got no legal authority. Inquiries can make valuable recommendations, but they are advisory in nature and cannot enforce legal changes or compel action.
There are numerous other examples where criminal trials have not led to the systemic-level changes that they highlight are urgently needed, beyond the individual verdict. During the trial of Hadiza Bawa-Garba – a junior doctor found guilty of manslaughter in November 2015 on the grounds of gross negligence manslaughter following the death of a six-year-old boy in her care – it was revealed that the Leicester NHS trust’s serious incident report had identified 93 failures, only six of which were attributable to the doctor herself.
Ultimately, 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.
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Amel Alghrani does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
– ref. Lucy Letby case: the problems with expert evidence – https://theconversation.com/lucy-letby-case-the-problems-with-expert-evidence-249309
