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July 2026: Government declines to widen the Thirlwall terms of reference (16 July) · new 100-page insulin report to the CCRC challenging the trial evidence (9 July) · Thirlwall report still expected no earlier than September · inquests relisted to 2027 · Shoo Lee Panel: no medical evidence of deliberate harm.

Lucy Letby Facts

Medical explainer

Air embolism (neonatal) — plain-English explainer

Air embolism is an obstruction of a blood vessel by a bubble of gas introduced into the circulation. In neonatal medicine it can occur through indwelling vascular catheters during routine line care. Air-embolism diagnosis in a living or recently-deceased baby normally requires objective evidence (radiology, post-mortem findings) plus a clinical context that fits.

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Why it matters in the Letby case

Several murder counts in the Lucy Letby case rest on a prosecution argument that skin-discolouration patterns described on the babies were diagnostic of deliberate intravenous air injection. The prosecution cited Lee & Tanswell (1989) Arch Dis Child as the authority. Dr Shoo Lee, the lead author of that paper, has publicly stated the descriptions on the trial record do not match the criteria in his paper. The Shoo Lee Panel found no objective evidence of air embolism in the cases reviewed.

Prosecution position

Crown experts described post-mortem skin-mottling patterns as classic findings of venous air embolism, citing Lee & Tanswell 1989. The jury was told the skin signs themselves, combined with Letby's shift presence, were diagnostic.

Expert challenge / post-conviction reading

Lee himself states the trial descriptions do not match his 1989 criteria (which describe large-vessel obstruction, not patchy mottling). The 14-member Panel he convened concluded no case reviewed met the diagnostic criteria. Independent neonatologists add that non-specific skin mottling is routine in collapsing preterm infants from any cause (sepsis, shock, NEC, cardiac failure).

What remains uncertain

Whether the CCRC will treat the expert dispute as fresh evidence sufficient to engage the 'real possibility' test under s.13 of the Criminal Appeal Act 1995.

Common questions

What is air embolism in a newborn?

An obstruction of a blood vessel by a bubble of gas that has entered the circulation. In neonatal medicine it can happen accidentally through indwelling vascular catheters during routine line care. Diagnosis normally needs objective evidence — radiology or post-mortem findings — plus a clinical context that fits.

Why does the Lee & Tanswell 1989 paper matter?

It was the authority the prosecution's expert cited for the diagnostic criteria. Its lead author, Dr Shoo Lee, has since said publicly that the skin signs described at the Letby trial do not match the criteria in his own paper.

Is skin mottling proof of air embolism?

No. Independent neonatologists describe non-specific mottling as a routine sign of major circulatory compromise from any cause, including sepsis, shock, necrotising enterocolitis and cardiac failure. The 1989 paper describes a different and more specific pattern.

What did the Shoo Lee Panel conclude about the air-embolism counts?

That the skin patterns described do not satisfy the diagnostic criteria of the 1989 paper, and that there is no medical evidence of air embolism in any indicted case reviewed.

Does this mean the convictions are unsafe?

This site takes no position on guilt. The convictions currently stand and the CCRC review has not concluded. What the expert record shows is that a diagnostic criterion relied on at trial is disputed by the author of the paper it came from.

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