May 2026: Thirlwall Inquiry report delayed to at least September 2026 · six-baby inquests relisted to 2027 · CCRC review active · Shoo Lee Panel: no medical evidence of deliberate harm.
The Crown presented Baby F's insulin reading of 4,657 pmol/L (paired with low C-peptide) as proof of exogenous insulin administration. The jury was told this was diagnostic of deliberate poisoning. The Roche Cobas immunoassay reading was treated as quantitatively reliable in the range reported.
The 4,657 pmol/L reading is at a magnitude more consistent with adult attempted-suicide insulin overdose (200+ units administered) than with the prosecution's theory of a small-volume spike in a slow-running TPN bag. At this assay range the Roche Cobas is vulnerable to the 'hook effect': at C-peptide concentrations above approximately 60,000 pmol/L the assay's sigmoidal response curve produces non-linear and unreliable readings that can be misinterpreted as exogenous-insulin-dominant patterns. The Royal Liverpool clinical biochemistry laboratory was using the 2010 protocol at the time of testing — the 2012 protocol (which explicitly acknowledges the laboratory cannot diagnose exogenous insulin from the Cobas result alone) came into force later. Confirmatory mass spectrometry, which the Roche manufacturer's own guidance requires for forensic use, was not performed. The sample-handling protocol (gel tubes; delayed centrifugation; storage conditions) did not meet the forensic standard.
A reading at 4,657 pmol/L, if real, would have killed Baby F. The fact that Baby F survived is itself evidence that the reading is not what the prosecution said it was.
The jury was told a high-insulin-low-C-peptide pattern is only explicable by exogenous insulin. The specific numerical value — 4,657 pmol/L — was presented as a measurement, not as a value requiring physiological cross-check. The hook effect was not explained. The manufacturer's requirement for confirmatory mass spectrometry was not a central feature of the Crown's case.
The Joint Expert Witness Insulin Report on Babies F and L (May 2025) sets out, in technical detail, why the Roche Cobas screening immunoassay cannot bear the evidential weight the trial placed on it. The Panel considers the insulin evidence falls below the standard required for a murder or attempted-murder conviction.