The 1989 paper in one sentence
Lee & Tanswell (1989), Archives of Disease in Childhood, 64(4): 507–510, describes a specific and recognisable clinical appearance in neonates who have sustained a large-volume venous air embolism from a central venous catheter: a striking, well-defined pattern of bright pink vessels against a pale background, which the paper attributes to gas locked inside large cutaneous vessels reflecting light differently from the surrounding blanched skin.
The paper’s key diagnostic claim — the thing that made it cited in teaching and subsequently in court — is that this pattern is a specific, recognisable sign of intravascular air, not a non-specific sign of any circulatory compromise. Without that specificity claim the paper is just a case series.
What the 1989 paper actually describes
From the paper’s own text (paraphrased to avoid direct quotation of copyrighted material):
- Bright pink vessels. The vessels themselves, clearly visible, appear a distinct bright pink against the surrounding skin. Not generalised mottling.
- Migrating pattern. The bright pink appearance moves as the infant moves, because the gas moves through the vessel with position change.
- Well-demarcated skin colour contrast. The affected skin is distinctly pale, not blotchy or partially cyanosed. The contrast between vessel and background is sharp.
- Anatomical localisation. The pattern appears over the area served by the affected central venous catheter — typically chest, abdomen, upper limbs.
- Temporal sequence. The pattern appears during or immediately after the embolic event; it does not emerge over a gradual deterioration.
What the prosecution described at trial
The descriptions put to the jury and recorded in contemporaneous reports describe a different appearance:
- Patchy mottling. Areas of irregular, non-demarcated colour change across the skin surface.
- Flitting discolouration. Patches of pink and pale skin appearing and disappearing across different areas of the body over time.
- Variable localisation. The appearance was not confined to the area served by an indwelling catheter; some descriptions placed it on the legs or back, areas inconsistent with an upper-body CVC-delivered embolus.
- Gradual onset. In several of the charged cases, the colour change emerged over a period of deterioration rather than appearing at a single event.
Where they diverge
The two descriptions diverge on the single most important diagnostic feature: specificity. The 1989 paper describes a specific, recognisable, sharply contrasted pattern attributable to locked intravascular gas. The trial descriptions describe non-specific mottling that is compatible with any number of causes of circulatory failure in a preterm baby: sepsis, NEC, cardiac failure, haemorrhage, or terminal shock.
This matters legally because the prosecution’s expert told the jury that the descriptions were diagnostic of air embolism on the authority of the 1989 paper. If the descriptions do not match the paper, the diagnostic claim collapses. Without the diagnostic claim, the “air embolism” allegation becomes an argument from general suspicion, not from a positive medical finding.
What Dr Shoo Lee has said himself
On 3 February 2025, at the London press conference at which the International Expert Panel reported its findings, Dr Lee stated in terms that:
- The skin patterns described at the Letby trial do not match the skin patterns described in the 1989 paper.
- In every alleged air-embolism case the Panel reviewed, the diagnostic criteria of the 1989 paper were not met.
- The Panel’s medical review found natural-causes explanations for every deterioration reviewed.
Our summary of the press conference is at the Panel press conference page. The original paper is at adc.bmj.com/content/64/4/507.
What independent neonatologists add
Specialists who have reviewed the record since point to additional evidence absent from the trial presentation:
- No post-mortem imaging showed intravascular air in any case. Radiographs or CT that would be expected to show locked gas in chambers of the heart, liver vasculature, or brain were negative.
- No histological findings at autopsy matched the classic air-embolism picture. The small foamy-appearing material described in some autopsy notes is, to pathologists familiar with the technique, an artefact of tissue handling and not a diagnostic finding.
- The anatomical localisation of the described colour change, in several cases, did not match the vasculature that an injected CVC embolus would affect.
Summary
The air-embolism claim was the central causation mechanism at the trial. It rests on a single 1989 paper. Line by line, the descriptions at trial do not match the descriptions in the paper. The lead author of the paper has said so in public and has convened an international panel that reached the same conclusion on case-by-case review. This is not a peripheral evidential dispute. It is load-bearing.