Prof. Jane Hutton — recruited by Cheshire Police, blocked by the CPS
The prosecution’s claim: The prosecution's statistical and epidemiological evidence was adequate for the purposes of the trial. The shift-chart analysis presented to the jury provided a valid basis for the jury to assess the improbability of the pattern of Letby's co-presence with adverse events.
Prosecution claim
The prosecution's statistical and epidemiological evidence was adequate for the purposes of the trial. The shift-chart analysis presented to the jury provided a valid basis for the jury to assess the improbability of the pattern of Letby's co-presence with adverse events.
Counter-evidence
In March 2018, Cheshire Police instructed Prof. Jane Hutton, a medical statistician at the University of Warwick, to conduct an independent statistical analysis of the cluster of neonatal deaths and collapses at the Countess of Chester Hospital. The CPS subsequently instructed Cheshire Police not to proceed with Prof. Hutton's engagement. This is a documented refusal to commission the independent statistical review that the investigation's own investigators had recognised as necessary. The Royal Statistical Society, in its 2022 commentary following the Sally Clark case review, specifically warned against prosecution decisions that block independent statistical review of mortality clusters in criminal cases, identifying this pattern as one of the structural failure modes in miscarriage-of-justice cases involving medical statistics. The Hutton block is therefore not an isolated procedural quirk — it is a specific instance of the conduct the RSS and wider statistical community have identified as a systemic risk factor in cluster-death prosecutions.
Key point: The CPS's instruction to Cheshire Police not to proceed with Prof. Hutton's independent statistical analysis is structurally similar to the expert-evidence failures the Royal Statistical Society identified in its review of the Sally Clark case — and is potentially one of the most significant single procedural facts in this case.
What the jury heard
The jury did not know that Cheshire Police had attempted to commission independent statistical review and had been blocked by the CPS from doing so. The jury was presented with the shift-chart analysis as an adequate basis for statistical inference without knowing that the investigating police themselves had sought a more rigorous independent analysis.
What the Panel says
The Panel did not opine directly on the Hutton block but the Royal Statistical Society's published commentary — specifically endorsing independent statistical review as the standard that should have been applied — provides the institutional framework for understanding the significance of the CPS's decision.
What independent experts add
- Prof. Jane Hutton is a medical statistician at the University of Warwick with expertise in clinical-trial methodology and healthcare statistics. Her instruction by Cheshire Police suggests the investigation itself recognised the need for rigorous independent statistical review.
- The Royal Statistical Society's 2022 report on the Sally Clark case explicitly warned against prosecution systems that block or fail to commission independent statistical review of mortality clusters.
- Prof. Richard Gill (Leiden), who was instrumental in the Lucia de Berk exoneration, has written publicly on the Hutton block as one of the most significant procedural concerns in the Letby case.
- The shift-chart presented to the jury — the statistical argument on which the prosecution's pattern case substantially rested — was never subjected to the independent methodological review that Prof. Hutton's engagement would have provided.
- The CPS's instruction is documented in the Hummingbird whistleblower report. The CCRC is in a position to request the underlying correspondence and assess the basis for the CPS's decision to block independent statistical analysis.