It's the fact that the deaths spiked after LL joined the ICU.
That the spike followed her to day shifts.
That the spike dropped when she was on holiday and working elsewhere.
That she was on duty for every collapse in the period studied. No-one else was.
That she altered notes to change her presence at the times of some incidents.
That many collapses & deaths occurred on milestone occasions. Something that could not occur coincidentally.
That she somehow has no recollection of two significant incidents re. collapses that a doctor and a parent remember acutely & say she was pivotally involved in.
That even LL agreed during the trial that insulin must have been put into the bags by someone.
So apparently there is an unapprehended attempted murderer of babies in that unit, or elsewhere. But somehow no-one else has had the factors above or below discovered about them to date.
In the wider picture,
That she refused, as much as was within her power, to take "breaks" from the ICU by working in the lower needs parts of the unit, as was common/advised for staff members.
That her inappropriate and odd behaviour was making other staff members and parents increasingly uncomfortable.
That everything found in her home and in her web browsing activities demonstrated an extremely unusual and pathological "interest" in the patients and families; gathering & retention of confidential medical notes that she had no reason (or right) to take home or retain, marking of babies deaths in her personal diary, some very disturbing written statements, with confessions to killing outnumbering denials etc. etc.
I could go on.
In general points;
Most of the NHS is understaffed and struggling. A medical professional serial killer is not mutually exclusive with that.
Incidents of medical negligence by medical professionals at some point in their career are also, sadly, common. Especially in high pressure situations. Especially with the tiniest and most delicate of all patients. Especially while gaining experience. Their occurrence at some point in some medical professionals careers are not mutually exclusive with the possible existence of a medical professional serial killer.
Their incidents of medical negligence, however, are unlikely to cluster/spike to the point where a unit becomes a weekly death zone and are beyond unlikely to coincidentally occur on baby's 100 day anniversary followed by their due date, on father's day, on transfer to other unit, with their prospects considered "optimistic" by medics (while LL declares them to "not making it out of here alive, is he?") and on their discharge day.
One milestone coincidence, unlikely in the extreme, but maybe ..... Multiple, no.