New concerns have emerged regarding the handling of the Lucy Letby case by Cheshire Police and the Crown Prosecution Service (CPS), as questions about the safety of her convictions continue to mount. Letby, a former nurse, was found guilty of murdering seven babies and attempting to murder seven others at the Countess of Chester Hospital in 2015 and 2016. Her new barrister, Mark McDonald, is preparing an application to the Criminal Cases Review Commission, supported by expert medical evidence from leading neonatologists who argue there are more plausible alternative causes for the babies' deaths and collapses.
Criticism has focused on the use of a shift chart during Letby's first trial, which showed which nurses were on duty when babies were allegedly attacked. Leading statisticians, including Professor Jane Hutton of the University of Warwick, have described this as a classic example of the 'prosecutor's fallacy', where a case is built to support a suspicion rather than exploring all possible evidence. Hutton stated: 'It's a large pile of crockery, much of which is broken. Such a pile does not hold water, however big it is.'
The Thirlwall inquiry, which opened in Liverpool last month, heard that the police investigation was based on statistical coincidence from the start. Documents show that seven doctors compiled a report in May 2017, noting that Letby was present at 11 of 13 deaths, and claimed the likelihood of this occurring by chance was very low. Hospital managers stated that when they approached Cheshire Police on 5 May 2017, they explained there was a 'notable high statistical relationship' between Letby and baby deteriorations, but no other evidence.
Emails seen by the Guardian reveal that Cheshire Police initially engaged Professor Hutton in April 2018, asking her to quantify the probability of one staff member being on duty during all deaths and collapses. She advised that a proper statistical inquiry should not focus on one individual from the outset, but instead examine all possible explanations, including medical conditions and unit performance. Despite this, the police proceeded with the investigation, and Letby's convictions have been upheld by the Court of Appeal.
