The insulin-assay peer-reviewed literature since 2023
Prosecution claim
The Roche Cobas insulin immunoassay result on Baby F was forensic proof of exogenous insulin administration. The jury was told 'you cannot argue with a lab result'.
Counter-evidence
Since the Letby convictions, specialist peer-reviewed clinical-biochemistry and endocrinology journals have published on the forensic use of immunoassay insulin results. The published picture is clear: immunoassays are screening tests, not forensic tests; false-positive rates are non-trivial from auto-antibodies, heterophilic antibodies, macro-insulin, assay interference, and drug cross-reactivity; sample-handling (gel tubes, delayed centrifugation, ambient storage) compromises forensic reliability; C-peptide dissociation is not specific to exogenous insulin; physiological plausibility of the reported numerical value fails Prof. Geoff Chase's modelling on the Crown's own TPN-bag theory. The Royal Liverpool laboratory's own 2012 protocol explicitly states it cannot diagnose exogenous insulin. No body of peer-reviewed work defends the Crown's framing against this literature.
The peer-reviewed clinical-biochemistry literature since 2023 is unanimous: the Roche Cobas screening result cannot bear the forensic weight the Crown placed on it. 'You cannot argue with a lab result' was wrong about this particular lab result.
What the jury heard
The Crown's framing of the Roche Cobas result as forensic proof. The peer-reviewed specialty consensus against this framing had not yet been published at the time of verdict.
What the Panel says
The Joint Expert Witness Insulin Report on Babies F and L consolidates the peer-reviewed literature into a case-specific report. Its conclusion: the insulin evidence cannot support a criminal finding of exogenous insulin administration.
What independent experts add
- Immunoassays are screening tests designed to flag samples for further investigation.
- Forensic distinction of exogenous from endogenous insulin requires mass spectrometry.
- Mass spectrometry was not performed on the Letby samples.
- Insulin auto-antibodies produce false positives; multiple clinical conditions produce the same pattern.
- Sample handling failed forensic standards.
- The Royal Liverpool laboratory's 2012 protocol explicitly acknowledges it cannot diagnose exogenous insulin.
- The physiological-plausibility modelling by Prof. Geoff Chase shows the reported value is inconsistent with the Crown's mechanism.
- No peer-reviewed post-Panel work defends the Crown's framing.