Statistical Analyses in the case of an Italian nurse accused of murdering patients

Abstract

Suspicions about medical murder sometimes arise due to a surprising or unexpected series of events, such as an apparently unusual number of deaths among patients under the care of a particular nurse. But also a single disturbing event might trigger suspicion about a particular nurse, and this might then lead to investigation of events which happened when she was thought to be present. In either case, there is a statistical challenge of distinguishing event clusters that arise from criminal acts from those that arise coincidentally from other causes. We show that an apparently striking association between a nurse's presence and a high rate of deaths in a hospital ward can easily be completely spurious. In short: in a medium-care hospital ward where many patients are suffering terminal illnesses, and deaths are frequent, most deaths occur in the morning. Most nurses are on duty in the morning, too. There are less deaths in the afternoon, and even less at night; correspondingly, less nurses are on duty in the afternoon, even less during the night. Consequently, a

Statistical Issues in Serial Killer Nurse Cases

“…The case of Ben Geen bears remarkable similarities with the cases of Lucia de Berk and Daniela Poggiali (Dotto et al 2022). However, whereas the conviction of de Berk was overturned after review and reopening, and that of Poggiali was overturned after cassation and reopening, all attempts to reopen the case against Geen have so far proven unsuccessful.…”

“…In the Lucia case, Elffers just trusted that the hospital data had been compiled in a responsible manner. In the case of Daniela Poggiali (Dotto et al 2022), a breakthrough was made when statisticians took a look at statistical aspects of the evaluation of toxicological evidence, following up on a hint from one of the medical experts for the defence. These cases are multidisciplinary; good multidisciplinary scientific research requires communication between all parties.…”

“…A nurse who clocks in early and clocks out late can appear to be present at many more deaths than other nurses, cf. the Poggiali case (Dotto et al 2022).…”

“…She spent a number of years in prison but was acquitted in 2021 at the Italian court of cassation. The first scholarly publication on the case is (Dotto et al 2022). Knowing the Italian justice system, this might not be the last word on the case, as far as legal history is concerned.…”