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Golden Dots

The Lucy Letby Case

Science on Trial was the first organisation to highlight the need for a new trial for Lucy Letby.  A neonatal nurse who was convicted of murdering and attempting murdering infants under her care at the Countess of Chester Hospital, UK.

Sarrita Adams, the founder of Science on Trial, was actively involved in re-examining the scientific claims made in the Lucy Letby case. Science on Trial, as an organization, is dedicated to ensuring responsible use of scientific evidence in the criminal justice system, with their first major project being advocating for a new trial for Lucy Letby, who was convicted of multiple crimes including murders and attempted murders of infants under her care at the Countess of Chester Hospital, UK​​.


Lucy Letby's trial, which began in October 2022 and lasted 10 months, involved a significant amount of circumstantial evidence and testimonies from medical expert witnesses. The prosecution's case largely centered around two babies identified with exceptionally high levels of insulin, leading to the theory that Letby had spiked the nutrient feed given to babies intravenously with insulin. Despite the evidence being described by the judge as "almost wholly, but not entirely, circumstantial," Letby was convicted on various counts, including murder and attempted murder​​.


Science on Trial's mission extends beyond just the pre-trial phase of cases.  As an organization we are focused on bridging the gap between scientific rigor and the quest for justice, aiming to improve the usage and interpretation of scientific evidence within the criminal justice system. This approach is evident in our efforts to highlight the poor scientific standard applied to the Lucy Letby case.


Reflecting our commitment to ensuring robust scientific investigation underpins every case​, Sarrita Adams and Science on Trial traversed a number of challenges in getting the legal community to acknowledge and consider their scientific review of the Letby case. This struggle highlights the broader issue of integrating scientific evidence and expertise into legal proceedings, particularly in complex cases like that of Letby, where the evidence is heavily based on medical and scientific interpretations.


Science on Trial’s major role in highlighting the lack of reliability in the Letby case underscores the importance of having specialized scientific input in legal cases, especially those involving complex medical evidence. Our assessment that Lucy Letby's trial may represent the greatest miscarriage of justice that the UK has ever witnessed, reverberated around the globe, and shed light on the way science can be distorted in the criminal justice system.   Science on Trial's work aims to bring a more balanced and scientifically-informed perspective to such legal proceedings, striving to ensure fair and just outcomes.

To view the original scientific analysis in the
Lucy Letby  Case: 


On Friday 18th August, 2023, at Manchester Crown Court, Lucy Letby was convicted of 14 crimes; 7 murders and 7 attempted murders.  Of the further 8 attempted murder charges, two were determined to be 'not guilty', and the remaining 6 were undecided.


Lucy served as an NHS nurse in the Neonatal Unit (NNU), at the Countess of Chester Hospital (CoCH), in Chester, UK, for several years, where she was described as a dedicated nurse with specialist training in ICU babies.  Between June  2015-2016 there were a particularly high number of infant deaths at the hospital, which also corresponded to an increase in stillbirths. It is alleged that the Consultant doctors on the NNU began to suspect that Lucy Letby was connected to the deaths, as she seemed to be present when they happened.  After considerable debate, she was suspended from her role on the ward in 2016 pending investigation. Nearly a year after her suspension, the police were called in, and a criminal case was opened.


Between July 2018 and November 2020, Lucy was arrested twice, and she was eventually charged in November 2020 with 23 counts: 8 murder charges and 15 attempted murder charges. One of the counts of murder was dropped before coming to court when the judge dismissed it, as the prosecution decided not to bring evidence for this death, which occurred in another hospital, after the child left CoCH's care three days prior.


The trial began in October 2022 and was predicted to last 6 months, it actually lasted 10 months.  During this time the prosecution presented five main medical expert witnesses who testified that they thought she was responsible for harming the babies. A considerable amount of circumstantial evidence was provided, including Facebook searches for some of the parents, handover notes, and a blood gas record brought to Letby's home, as well as anecdotal evidence from parents and doctors that they felt Lucy had behaved inappropriately at times.


The prosecution weaponized evidence against Lucy. On one occasion, nearly a year after she had been suspended, she wrote a letter to a couple of twin babies who had passed away expressing her sadness that they had died. She also sent a sympathy card to one bereaved family, before she was suspended, apologizing she couldn't accept their invitation to come to the funeral and photographed the card, as she also photographed other cards not connected with the case. Finally, Lucy wrote a note which is generally agreed to have been written after she knew she was being investigated, which said "I killed them on purpose because I'm not good enough", "I'm not good enough to live" and "I AM EVIL I DID THIS". But it also had conflicting statements saying things such as "I haven't done anything wrong", citing persecution from others and hatred. There were many other notes found at her house protesting her innocence.


The judge, presiding over the case, called the evidence "almost wholly, but not entirely, circumstantial".  However, at the heart of the case were two babies who were identified in 2018 by Dr Brearey, a consultant at CoCH, as having exceptionally high levels of insulin.  The high insulin concentration led to the prosecution witnesses' theory that Lucy had spiked the nutrient feed, given to babies intravenously, with insulin to cause the infants deliberate harm.   Lucy Letby testified in her own defense, stating that she had never harmed children in her care.  After 14 days on the stand, Lucy Letby's barrister called one other witness, the maintenance man, contracted by CoCH, who confirmed Lucy's testimony that at times there had been raw sewage on the neonatal ward or neighboring wards. The defense also showed that she made facebook searches of different people, not connected with the case, and had a house full of handover notes, not only those connected with the case. The defense did not, however, bring any medical witnesses to challenge any of the medical evidence and relied on cross examination of prosecution witnesses only.


The jury took weeks to reach their final verdicts. On 18th August, 2023, after over 100 hours of deliberation, and where one juror was recently removed, Lucy Letby was convicted unanimously on both the cases of insulin poisoning, and one murder of child O, whose liver showed significant damage in the post mortem. She was convicted on 10 other counts with a majority verdict of 10-1, including all the other murder cases. She was found not guilty of two charges of attempted murder, and the jury failed to reach a verdict on the remaining 6 charges.


We believe that Lucy's defense was not adequate, that there is more to this case which was not heard in court, which deserved to be heard, and that everyone deserves a fair trial. That is why we have come together to fight for the science to be brought to trial.  


of successful appeals are based on the same materials presented at the trial


of convictions were overturned due to improper interpretation of scientific evidence


of convictions were overturned due to inaccurate expert witness testimony

Expert Witnesses:
Challenging reliability.

Following the verdicts, it was revealed that Lucy Letby's Barrister, Benjamin Myers, KC, sought to have the expert witness evidence of Dr Dewi Evans dismissed from the case.  The Judge presiding over the case denied the Barrister's application stating that it is for the jury "to determine, as with any witness, his reliability, having regard to all the evidence in the case."

This decision to permit Dr Evans evidence is controversial, as permitting the jury to evaluate expert witness testimony is distinct from that of a general witness.  It was previously found that, “In determining the issue of admissibility, the court must be satisfied that there is a sufficiently reliable scientific basis for the evidence to be admitted. If there is then the court leaves the opposing views to be tested before the jury.” R v Dlugosz [2013] EWCA Crim 2, [2013] 1 Cr App R 32 at [11]”

At issue is the reliability of the evidence on a scientific basis.  It is evident that none of the normal practices used to determine air embolism as a cause of death were applied by Dr Evans, and the one publication he referred to does not relate to air embolism through ambient air entrainment in the vasculature.  Dr Evans determined that the infants died due to air embolism by referring to a 1989 research paper, which described gas embolism, due to the usage of high ventilation pressures which is a practice no longer applied to neonates.  None of the findings on autopsy suggest the children died due to air embolism.​

It is apparent that a crucial element in the Lucy Letby case is the reliability of the original investigation.  It is of great concern that Dr Evans conducted the investigation with the assistance of the consultants who were present on the ward at the time of death, and where, in any other setting, such individuals should have been treated as suspects.  A further factor is whether Dr Evans was qualified to conduct any investigation given that he is neither a forensic scientist, nor a pathologist.  Dr Evans has no formal training or background in the principles of scientific research.  It is highly irregular for a group of medical doctors to play a primary role in carrying out a criminal investigation.  In most other jurisdictions such activity would not constitute an independent investigation.

Regarding the issues surrounding the reliability of expert evidence in criminal courts in England and Wales, the Department of Justice stated:

"...there is no robust estimate of the size of the problem to be tackled – either in terms of the number of cases where unreliable expert evidence is adduced, nor in the impact this has in terms of subsequently quashed convictions.”


UK Ministry of Justice (2013)

Government Response to Law Commission Report on Expert Evidence

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