At first glance, the case against Lucy Letby seemed overwhelming but the neo-natal nurse pleaded not guilty to 22 charges of murder and attempted murder, arising from the deaths of an abnormally high number of newborn babies in her Countess of Chester Hospital.
Thousands of pieces of evidence were gathered for the first 10-month trial into Letby’s case, which led to her conviction in 2023 for the murder of seven babies and attempted murder of six more – after around 110 hours of jury deliberations.
But ahead of a Thirlwall Inquiry into the baby deaths, being launched next week, statisticians, armchair detectives, politicians and criminal experts are among those demanding a fresh look at the evidence that convicted Letby to 15-whole life orders.
A search of Letby’s Chester home found a number of Post-it notes, on which she had written: “I killed them on purpose because I’m not good enough”, “I am a horrible person”, and “I am evil I did this”.
The Guardian has reported that Lucy Letby scribbled the notes on the advice of her GP and hospital bosses to cope with her feelings of extreme stress about being under investigation for the unexpected deaths.
In excerpts from police interviews, Letby said: “I just wrote it because everything had got on top of me. It was when I’d not long found out I’d been removed from the unit and they were telling me my practice might be wrong, that I needed to read all my competencies – my practice might not have been good enough.
“I was blaming myself but not because I’d done something (but) because of the way people were making me feel.”
Letby herself spent 14 days in the witness box, facing close to 60 hours of questioning. The prosecution highlighted instances in her testimony in which Letby appeared to contradict her own evidence to police, or disputed evidence she had previously agreed with.
Speaking to Sky News after her guilty verdicts, prosecution expert witness Dr Dewi Evans suggested the “smoking gun” had been when two of the babies were found to have very high levels of unprescribed insulin in their blood, which Letby herself conceded would mean they had been “deliberately” attacked, but again insisted: “Not by me.”
In September 2023, the Royal Statistical Society wrote to the chair of the newly announced public inquiry into the Letby case to warn generally that “it is far from straightforward to draw conclusions from suspicious clusters of deaths in a hospital setting”.
Expressing hope “that lessons from such cases in the past will be learnt”, the society’s leaders wrote: “It is a statistical challenge to distinguish event clusters that arise from criminal acts from those that arise coincidentally from other factors, even if the data in question was collected with rigour.”
One key piece of statistical evidence was the rota data which suggested Letby was always on shift when babies in the neonatal unit where she worked took an unexpected turn for the worse.
While one such chart listed 25 collapses and fatalities in which Letby was present, the jury was not told about a further nine deaths over that period with which she was not charged, which were not included in the table, according to The Daily Mail.
A source said: “Four of the deaths were babies born with a congenital problem or birth defect, another baby was sadly asphyxiated or deprived of oxygen at birth, the remaining four died of infection and their deaths were precipitated with a period of time consistent with infection – they did not suddenly and unexpectedly collapse and die.”
The first review into the deaths was commissioned in July 2016, after fatalities at the unit rose from four each year in 2013-14 to an unusual spike of 13 deaths in the year to June 2016. That review found the unit was understaffed, with junior staff left feeling unable to call in consultants.
Cheshire Constabulary has not commented on the decision not to include the additional nine deaths in the table used in evidence.
One source of doubt originates in amended evidence offered when Letby was retried for, and found guilty of, one count of attempted murder.
Consultant paediatrician Dr Ravi Jayaram told the court that he had become increasingly concerned about Letby, following a spike in the number of baby deaths in the unit. When he realised that Letby was on her own with Baby K, he went into the nursery to reassure himself that everything was OK.
Dr Jayaram said he caught her “virtually red-handed” as he entered Nursery 1 at about 3.45am and he then went on to intervene and resuscitate Child K.
