Facebook searches — the denominator problem
Prosecution claim
The Crown's trial narrative presented Facebook searches made by Ms Letby for families of deceased and collapsed babies as evidence of abnormal, incriminating post-incident interest in the victims. The jury was invited to read the searches as consistent with the psychology of a perpetrator.
Counter-evidence
The search data, read with its denominator, dissolves the 'trophy' framing. The raw numbers show Facebook searches for families of many more babies than those on the indictment — distributed across a large population of families on the unit during Letby's tenure, not clustered around the deaths. Many searches relate to babies who survived, to routine post-discharge curiosity, and to normal NICU nursing familiarity with families. The base-rate comparison — what a typical neonatal nurse's Facebook activity looks like — was not before the jury. When the denominator is included the 'searches-as-incriminating' framing is not sustainable on the data.
The denominator is everything. A handful of searches out of hundreds, distributed across families of surviving and non-indicted babies as much as around deaths, is not a pattern. The prosecution presented the numerator; the defence could show the denominator; the jury weighed them; the appellate reader can re-weigh them once the denominator is visible.
What the jury heard
The jury heard specific searches highlighted against the emotional weight of the indictment. The defence cross-examination addressed the broader pattern. The Crown's closing emphasised selected searches without systematic denominator framing.
What the Panel says
Not applicable — the Panel's scope is clinical. But independent clinical-psychology commentators have noted that Facebook curiosity about patients is documented baseline behaviour in NICU nursing populations, not itself probative of criminal intent.
What independent experts add
- The raw data in the evidence gallery (lucyletbyinnocence.com) allows direct base-rate calculation.
- Searches are spread across a population of families larger than the indictment, and often for babies who survived.
- The temporal distribution of searches does not cluster tightly around deaths — it spreads over the duration of employment.
- Facebook searches by nurses for patients' families is an ethically grey but documented behaviour in NICU cultures (where nurses often form sustained clinical relationships with families).
- Base-rate absence is itself a structural evidential problem the Crown's case does not address.
- The searches-as-incrimination framing relies on the jury not having a comparator — the comparator is absent from the trial record.
- Independent commentators (Dr Phil Hammond and others) have addressed the denominator problem in public writing.