The Shoo Lee Panel — February 2025 baseline
The Shoo Lee International Expert Panel was convened following the convictions and reported in February 2025. The Panel comprised senior neonatologists, paediatric pathologists, and clinical biochemists drawn from the United Kingdom, Canada, the United States, Australia, and continental Europe. Its remit was to review each of the incident cases independently, assess the evidence presented at trial, and provide case-by-case opinions on whether natural-cause explanations were available.
The Panel’s February 2025 report concluded that, for each incident reviewed, there were one or more natural-cause explanations consistent with the clinical presentation, the post-mortem findings, and the documented medical context. The Panel found that the prosecution’s expert evidence had, in several cases, not adequately considered or excluded available natural-cause differentials, including extreme prematurity complications, infection, necrotising enterocolitis, and resuscitation-related injury.
The Panel’s report was accompanied by a press statement at which Dr Shoo Lee presented the Panel’s collective findings. The Panel was explicit that its conclusions were independent of any legal process and were directed at the scientific question of whether the medical evidence supported the prosecution’s proposed mechanisms of harm.
The Joint Insulin Report — May 2025
In May 2025, a joint report on the insulin evidence relating to Babies F and L was published by a group of clinical biochemists and endocrinologists with expertise in insulin assay methodology. The insulin evidence was central to several of the most serious counts in the prosecution and had been described by the Crown as among its most compelling physical evidence.
The Joint Insulin Report addressed two distinct questions. First, whether the assay methods used to measure insulin levels in the samples from Babies F and L were sufficiently validated for use in a forensic context involving neonatal samples. Second, whether the C-peptide suppression pattern relied upon by the prosecution was, as the Crown alleged, diagnostic of exogenous insulin administration.
According to the report, the assay methodology used had not been validated for neonatal samples, and the reference ranges applied were derived from adult populations. The report further found that C-peptide suppression, while consistent with exogenous insulin administration, is also observed in certain neonatal hypoglycaemic states and in the context of post-mortem sample degradation. The report concluded that the insulin evidence, as presented at trial, overstated the diagnostic certainty of the exogenous- administration finding.
Independent paediatric-pathology re-readings — October 2025
In October 2025, a series of independent post-mortem re-readings by paediatric pathologists who had not been involved in the original trial examinations were published. These re-readings covered a subset of the cases in which post-mortem findings had formed a significant part of the prosecution evidence.
The re-readings identified several instances where findings characterised by prosecution pathologists as indicating inflicted injury were re-assessed as consistent with natural disease processes or resuscitation trauma. Specifically, retinal haemorrhages, rib-related findings, and patterns of petechial haemorrhage that had been attributed to compression or traumatic causation were re-read by independent pathologists as within the range expected in the context of extreme prematurity, prolonged resuscitation, or sepsis.
The October 2025 re-readings did not constitute a formal systematic review but represented the first structured independent pathological assessment of a portion of the physical evidence presented at trial. The findings were consistent with the Panel’s February 2025 conclusions and added pathology-specific weight to the broader post-trial scientific record.
RCPCH updated guidance — March 2026
In March 2026 the Royal College of Paediatrics and Child Health published updated guidance on the role of expert evidence in neonatal-death prosecutions. The guidance was explicitly described as arising in part from reflections on recent cases — without naming the Letby case specifically — in which the college judged that the standard of expert evidence had not met the requirements for forensic use in criminal proceedings.
The updated guidance addressed three areas. It set out standards for the validation of diagnostic methods before they are used to support criminal allegations; it recommended that paediatric expert witnesses explicitly address natural-cause differentials in written reports rather than leaving their exclusion implicit; and it called for a structured multi-disciplinary approach to expert opinion in neonatal-death cases, rather than the single-expert model that the guidance acknowledged had been used in several recent prosecutions.
Royal Statistical Society reissued warning — April 2026
The Royal Statistical Society reissued and updated its warning on the use of shift- attendance statistical arguments in criminal proceedings in April 2026. The original warning — initially developed in the context of the Sally Clark case in 2001 — had highlighted the prosecutor’s fallacy and the risks of presenting co-occurrence statistics as probative of guilt.
The April 2026 reissued statement addressed the specific form of shift-attendance argument used in the Letby trial — in which the statistical overlap between Letby’s shift patterns and the timing of incidents was presented as corroborating guilt — and identified several methodological concerns. These included the absence of a defined reference class for comparison, the failure to account for base-rate variation in neonatal deterioration across shifts, and the risk of circular reasoning when shift-pattern evidence is presented alongside clinical-suspicion evidence that was itself partly generated by the same shift-pattern observation.
Where the consensus sits today
Taken together, the post-trial scientific record as of April 2026 reflects convergent concern across multiple independent disciplines. UK and international neonatology, through the Shoo Lee Panel, has concluded that natural-cause explanations are available for each incident. Clinical biochemistry, through the Joint Insulin Report, has identified significant methodological limitations in the assay evidence. Paediatric pathology, through the October 2025 re-readings, has offered alternative interpretations of key physical findings. Professional bodies in paediatrics and statistics have both issued guidance or warnings that, implicitly or explicitly, reflect on the standards applied in this case.
This convergence across disciplines is material to the CCRC’s review under the section-13 test. Supporters of a referral argue that the breadth and consistency of post-trial scientific concern, spanning multiple specialties and jurisdictions, is precisely the kind of post-conviction scientific development that the CCRC pathway was designed to address.