What the inquiry was set up to do
The Thirlwall Inquiry was established by the Secretary of State for Health and Social Care in May 2024, chaired by Lady Justice Thirlwall. Its remit was to examine the circumstances at the Countess of Chester Hospital’s neonatal unit during 2015–2016 — specifically the governance structures, escalation mechanisms, and institutional responses to consultant and nursing concerns about unexplained deteriorations and deaths among neonates in that period.
The inquiry’s terms of reference were expressly limited to institutional and regulatory matters. They did not permit re-examination of the evidence presented at the criminal trial, assessment of whether the convictions were safe, or any finding that would bear directly on the legal questions now before the CCRC. This was not an oversight — it was a deliberate boundary set at the outset to avoid the inquiry prejudicing or interfering with parallel legal processes. Lady Justice Thirlwall acknowledged this limitation repeatedly during evidence hearings.
What the final report is expected to address
Based on the public evidence sessions, opening statements, and the structure of the Inquiry’s terms of reference, the final report is expected to reach conclusions across a number of institutional domains. On board governance, the question is whether non-executive directors at the Countess of Chester Hospital received adequate information about the scale or significance of the neonatal mortality elevation during 2015–2016, and whether escalation pathways within the trust were robust enough to surface concerns originating at consultant and nursing level to board-level attention in a timely way. The evidence put before the Inquiry strongly suggests they were not.
On executive responses, the report is expected to examine how senior managers responded once consultant paediatrician concerns were raised. The decisions about whether to refer matters externally — to the Royal College of Paediatrics and Child Health (RCPCH), to NHS England, or to the police — were, on the evidence heard, delayed and poorly coordinated. (The Operation Duet corporate-manslaughter investigation, separately, has produced criminal arrests of three former senior leadership members on 30 June 2025, with one re-arrested on 23 April 2026 for perverting the course of justice — see our April 2026 arrest analysis.)
On regulatory oversight, the report is expected to review the role of the Care Quality Commission (CQC) and NHS England during the relevant period — whether the regulatory framework provided adequate mechanisms for identifying and acting on mortality signals at unit level in real time. Recommendations on mandatory mortality-signal reporting thresholds, board-level accountability for neonatal governance, and the role of royal college oversight visits in triggering regulatory action are widely anticipated.
Where the carve-out matters
The conviction-safety carve-out is significant because a substantial portion of public and media attention on the inquiry has focused on questions that fall squarely outside its terms of reference: whether the expert evidence at trial was reliable, whether the statistical shift-pattern argument was valid, and whether the insulin assay evidence was correctly interpreted. The inquiry has heard no expert evidence on these scientific questions and will reach no conclusions about them.
This creates a risk of public misreading once the report is published. Findings that institutional failures occurred — that governance was inadequate, that escalation was slow — will be institutional conclusions. They will not, in themselves, address whether Lucy Letby committed the acts she was convicted of. Equally, the report’s silence on conviction safety will not constitute an endorsement of the convictions. The two domains are legally and analytically separate.
Supporters of a CCRC referral note that the institutional findings, when published, will be potentially relevant to the broader picture: if governance was poor and escalation was inadequate, then the trajectory of clinical deteriorations and deaths at the unit was being managed within a system with significant structural weaknesses — a context that bears on how natural-cause explanations should be weighed.
How the findings will interact with the CCRC review
The CCRC review, confirmed publicly by chair Dame Vera Baird in February 2026, is examining the scientific and evidential basis of the convictions. The Thirlwall report, once published, will be a separate process — but its findings may become material in at least two indirect ways.
First, the Shoo Lee International Expert Panel, whose February 2025 report assessed the medical evidence case by case, operated as a parallel scientific review with no formal connection to either the inquiry or the CCRC. The Panel’s findings — that natural-cause explanations exist for each incident — are the primary scientific input to the CCRC process. The Thirlwall report is expected neither to endorse nor to contradict the Panel; they address different questions.
Second, if the CCRC ultimately refers the case to the Court of Appeal, the court will consider fresh evidence in the round. The institutional picture established by the Thirlwall report, when published, may form part of the broader factual context, though its direct evidential weight in a criminal appeal will depend on how the court defines the scope of fresh-evidence review.
What now — and the knock-on effect on the inquests
On 13 May 2026 the HM Coroner relisted the inquests into the deaths of six of the babies Letby was convicted of murdering — the full hearings, originally scheduled for September 2026, will now provisionally begin on 10 May 2027. The coroner cited the need for the Thirlwall Inquiry’s findings to be fully considered before the inquests proceed. See our inquests-delayed-to-2027 analysis. The 2026 timetable of converging formal-record processes — Thirlwall report, inquests, CCRC pathway — will instead unfold sequentially across 2026 and 2027.
When publication eventually occurs, the conviction-safety question will remain entirely with the CCRC. The Thirlwall report will not accelerate or constrain that process, but it will close the inquiry phase of the institutional examination of the Countess of Chester Hospital. Government has committed to responding to the recommendations within a defined period.