Expert-consensus threshold — how much disagreement makes a conviction unsafe
Prosecution claim
The Crown's case at trial relied on the opinion of Dr Dewi Evans, supported by Dr Sandie Bohin. The jury was entitled to accept that expert opinion over any defence disagreement. That is how jury-trial expert evidence is meant to work.
Counter-evidence
The Cannings principle (Court of Appeal, December 2003) sets the operative threshold: where a conviction depends on medical expert evidence, and reputable medical experts disagree about the cause of the death or injury, the conviction is unsafe. The post-conviction expert record in the Letby case is a record of fourteen senior international neonatologists on the Shoo Lee Panel, the Joint Insulin Report authors, the independent paediatric pathologists on the CCRC application, Prof. Richard Gill, Prof. Peter Green, Prof. Geoff Chase, and the peer-reviewed neonatology journal layer all disagreeing with the Crown's causation experts on every indicted case. This is substantially more expert disagreement than Cannings, Clark or Anthony had. The Cannings threshold is therefore met and exceeded.
The Cannings principle does not require a unanimous acquittal by experts. It requires reputable expert disagreement. On the Letby record, the disagreement is not merely reputable — it is internationally institutional.
What the jury heard
The Crown's experts and, to a lesser extent, the defence experts. The jury did not have the post-conviction expert record available.
What the Panel says
The Panel's finding that medical evidence of deliberate harm is absent in every case reviewed is the operative professional finding. Fourteen signatories from eight countries is a strong institutional form of the reputable-expert-disagreement the Cannings principle addresses.
What independent experts add
- The Cannings threshold is reputable expert disagreement, not unanimous expert acquittal.
- The Shoo Lee Panel comprises fourteen senior international specialists.
- The Joint Insulin Report adds specialised endocrinology / clinical-biochemistry signatories.
- Independent paediatric pathology re-readings add further specialist signatures.
- Prof. Richard Gill and Prof. Peter Green add the statistical layer.
- Prof. Geoff Chase adds the physiological-modelling layer.
- Peer-reviewed neonatology journals have published commentary and editorial supportive of the Panel's methodology.
- No body of peer-reviewed post-Panel work has emerged defending the Crown's methodology.
- The disagreement is not only reputable but internationally institutional.