In two cases, the victim died by insulin overdose, Letby herself admitted that the only possible explanation was foul play. That means there is a killer on the ward. The police interviewed the other nurse on the shift, and she was cleared. Even if Letby gets acquitted from the other cases, her sentencing likely will not change.

One challenge for the defence was that there are few studies on injecting air in small babies for obvious reasons. Air embolisms are very painful, and such a study wouldn't pass ethics approval, let alone parental consent.