Interview With Prof. John O'Quigley On Lucy Letby

Professor John O'Quigley, honorary professor of statistics at University College London, presents original published research demonstrating that the shift-statistics chart is statistically inert. Using a proportional hazards model and a beta-binomial distribution fitted to the non-accused nurses' presence data, he shows that the probability of Letby being present at 25 or more suspicious events — given how frequently she worked — is approximately 10%, not the near-100% implied by the chart. He explains that the chart's continuous row of dots for Lucy Letby tells the observer nothing meaningful, because the data it represents is contaminated by selection bias: suspicious events were defined partly by her presence. He reconstructs the statistical picture using only the data from non-accused nurses and shows that when hours worked are controlled for, the apparent anomaly disappears entirely for the hardest-working nurses. He also reads from Rachel Aviv's New Yorker article and Nick Johnson's cross-examination to demonstrate the centrality of the chart to the prosecution's case.

Last updated 2026-07-14

2 min read

Notable extracts

Short verbatim extracts from the video. Each quote is under 80 words and attributed to the speaker. Extracted under fair-dealing for review and news reporting (CDPA 1988 s.30).

Prof. John O'Quigley

The continuous row of dots for nurse 23 is the only part of that chart that tells you nothing. Paradoxically, it is the part everyone looks at. The information is in the other nurses.

On the information content of the shift chart

Prof. John O'Quigley

When you control properly for the number of shifts worked and use the non-accused nurses as your baseline, the probability of her presence being anomalous is around ten percent. Not one hundred percent. Ten.

On the result of his published statistical analysis

Prof. John O'Quigley

Nick Johnson said: if they were attacked, and you are the only common feature, it would have to be you. He is getting that from the chart. And the chart, as I have shown, has no statistical value.

On the prosecution's use of the shift chart in cross-examination

Interview With Prof. John O'Quigley On Lucy Letby

Last updated 2026-07-14

2 min read

Notable extracts

Short verbatim extracts from the video. Each quote is under 80 words and attributed to the speaker. Extracted under fair-dealing for review and news reporting (CDPA 1988 s.30).

Prof. John O'Quigley

The continuous row of dots for nurse 23 is the only part of that chart that tells you nothing. Paradoxically, it is the part everyone looks at. The information is in the other nurses.

On the information content of the shift chart

Prof. John O'Quigley

When you control properly for the number of shifts worked and use the non-accused nurses as your baseline, the probability of her presence being anomalous is around ten percent. Not one hundred percent. Ten.

On the result of his published statistical analysis

Prof. John O'Quigley

Nick Johnson said: if they were attacked, and you are the only common feature, it would have to be you. He is getting that from the chart. And the chart, as I have shown, has no statistical value.

On the prosecution's use of the shift chart in cross-examination

Interview With Prof. John O'Quigley On Lucy Letby

Notable extracts

Related on this site

Interview With Prof. John O'Quigley On Lucy Letby

Notable extracts

Related on this site