The judge's directions on this - (snipped for the relevant parts)
“It would, you may think, be a remarkable and exceptional case in which a jury could say we know everything about what happened in any case and why.
“You are not detectives.
“If you are sure that someone on the unit was deliberately harming a baby or babies, you do not have to be sure of the precise harmful act or acts. In some instances there may have been more than one.
“To find the defendant guilty, however, you must be sure that she deliberately did some harmful act to the baby the subject of the count on the indictment and the act or acts was accompanied by the intent and, in the case of murder, was causative of death.”
[...]
“If you are satisfied so that you are sure in the case of any baby that they were deliberately harmed by the defendant then you are entitled to consider how likely it is that other babies in the case who suffered unexpected collapses did so as a result of some unexplained or natural cause rather than as a consequence of some deliberate harmful act by someone.
“If you conclude that this is unlikely then
you could, if you think it right,
treat the evidence of that event and any others, if any, which you find were a consequence of a deliberate harmful act,
as supporting evidence in the cases of other babies and that the defendant was the person responsible.
“When deciding how far, if at all, the evidence in relation to any of the cases supports the case against the defendant on any other or others,
you should take into account how similar or dissimilar, in your opinion, the allegations and the circumstances of and surrounding their collapses are."
The nurse is accused of murdering seven babies and trying to murder 10 others while working on the neonatal unit at the Countess of Chester Hospital.
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