My understanding is that a great deal of the case was based on probability.
Yes, and there have been significant concerns and suggestions that the statistical evidence regarding Lucy Letby's shift patterns was misrepresented or misunderstood during her trial:
Selective Data Presentation: "Critics, including statisticians and academics, have argued that the shift chart used in the trial was misleading because it only included incidents associated with Letby's presence, omitting other incidents where she was not on duty. This selective presentation was described as "cherry-picked data" by some, suggesting that the chart was designed to show a correlation where one might not have been conclusively established."
Scientific Worthlessness: "Meetings at the Royal Statistical Society (RSS) have discussed how the shift pattern data was 'scientifically worthless.' Experts have criticized the data for not being reproducible independently and for not accounting for other variables that could explain the incidents, like the natural variation in death rates or the presence of other nurses during shifts."
Misleading Correlation: "There's been commentary on the 'lottery fallacy' concept, where the rarity of an event is confused with causation. In Letby's case, the high correlation of incidents with her shifts was taken to imply causation, which many experts argue is a flawed statistical interpretation."
Alternative Explanations: "Various sources have pointed out that alternative explanations for the high incidence of collapses and deaths, such as understaffing, hospital conditions, or even natural statistical variation, were not adequately considered. This has led to arguments that the statistical evidence was over-interpreted or misused."
Expert Criticism: "Prominent statisticians like Richard Gill and Peter Green have publicly questioned the validity of the shift data as presented in court. They've highlighted the lack of a comprehensive statistical analysis that would account for all relevant factors, not just the presence of Letby."