Child L — insulin/C-peptide discordance and dual-sample protocol failure
The prosecution’s claim: The Crown argued Child L's blood sample showed an insulin level inconsistent with C-peptide, a pattern said to be diagnostic of exogenous insulin and therefore proof of deliberate poisoning.
Prosecution claim
The Crown argued Child L's blood sample showed an insulin level inconsistent with C-peptide, a pattern said to be diagnostic of exogenous insulin and therefore proof of deliberate poisoning.
Counter-evidence
The Roche Cobas immunoassay used is a screening test. Its manufacturer requires confirmatory mass spectrometry before any forensic conclusion can be drawn. That confirmation was never performed for Child L. The dual-sample protocol that would allow assay-interference and sample-degradation to be ruled out (paired venous and arterial samples, immediate centrifugation, mass-spec confirmation, Guildford reference-laboratory handling) was not followed. The Joint Expert Witness Insulin Report on Babies F and L sets each of those problems out in technical detail. The Shoo Lee Panel's own conclusion is more direct still: Child L's insulin/C-peptide ratio was within the range normal for preterm infants, and does not prove exogenous insulin. The Panel attributes Child L's hypoglycaemia to preterm birth and severe intrauterine growth restriction, and finds that its management was inadequate.
Key point: The Panel found Child L's insulin/C-peptide ratio to be within the range normal for preterm infants. The hypoglycaemia is explained by prematurity and severe growth restriction — inadequately managed.
What the jury heard
Royal Liverpool laboratory biochemists described the screening result as inconsistent with endogenous pancreatic release. The jury was not told that the manufacturer requires confirmatory mass spectrometry for forensic use, that the dual-sample protocol was not followed, or that dextrose treatment itself suppresses C-peptide.
What the Panel says
The Panel finds that Child L's hypoglycaemia was caused by preterm birth and severe intrauterine growth restriction, and that its management was inadequate. The insulin/C-peptide ratio is within the norm for preterm infants and does not prove exogenous insulin.
What independent experts add
- The Panel makes the same finding for Child F: the insulin/C-peptide ratio is within the range normal for preterm infants and does not prove exogenous insulin.
- The assay and protocol failures apply to both babies; the Joint Expert Witness Insulin Report on Babies F and L addresses them together.
- Adel Ismail has published detailed commentary on Cobas-assay interference rates in neonates.
- Our /evidence/insulin entry sets out the broader methodological problem with the Liverpool insulin testing.