A group including some of the UK’s leading neonatal experts and professors of statistics is calling on the government to postpone or change the terms of a public inquiry over concerns about the conviction of the neonatal nurse Lucy Letby. In a private letter to ministers, seen by the Guardian, the 24 experts said they were concerned that the inquiry’s narrow terms could prevent lessons being learned about “possible negligent deaths that were presumed to be murders” in the neonatal ward of the Countess of Chester hospital (CoC). The public inquiry, led by Lady Justice Thirlwall, was set up last September after Letby was found guilty of the murder of seven babies and the attempted murder of six others at the hospital. The inquiry was adjourned until after Letby’s retrial on a charge on which the original jury had been unable to reach a verdict. That trial, which concluded in July, resulted in her being found guilty of the attempted murder of another baby. Four judges have refused Letby leave to appeal the first verdicts; an application to appeal the later verdict is understood to be pending. Despite the convictions and court of appeal decision, there has been a small but growing number of experts raising concerns about the evidence presented at trial. Several came forward in an article published by the Guardian in July, expressing concerns that Letby’s conviction was unsafe. Only seven of the 24 signatories of the letter, which was sent last month to the health secretary, Wes Streeting, and the justice secretary, Shabana Mahmood, are experts who have previously spoken publicly about their concerns. The other signatories are voicing their concerns formally for the first time. They include Dr Tariq Ali, the former head of the paediatric critical care unit at Oxford university hospitals, and Philip Dawid, an emeritus professor of statistics at the University of Cambridge. Others raising questions about the Letby case include Jane Hutton, a professor of statistics at the University of Warwick, Prof Gillian Tully, a leading expert in forensic science, and Dr Neil Aiton, a consultant neonatologist who is also a medical expert witness with more than two decades’ experience. Describing themselves as “a diverse group of doctors, nurses and scientists” who have independently examined the Letby case, they stressed they were “not associated with Ms Letby or her defence, nor are we driven by emotional reactions to the case. Our approach is rooted in scientific analysis and concern for systemic issues within healthcare and the justice system. “While we acknowledge the gravity of the convictions against Ms Letby, our focus is on the broader implications for patient safety, healthcare management, and the potential for miscarriages of justice in complex medical cases. We believe that legal systems are particularly vulnerable to errors when dealing with intricate scientific evidence, especially in cases involving statistical anomalies in healthcare settings, and the complex physiology of neonates.” Taking issue with one strand of the Thirlwall inquiry, which relates directly to Letby, they said the natural assumption following the convictions – that she was a murderer – may lead to “a failure in understanding and examining alternative, potentially complex causes for the deaths, thus missing important lessons. Possible negligent deaths that were presumed to be murders could result in an incomplete investigation of the management response to the crisis”. The Thirlwall inquiry’s main hearings are due to begin in Liverpool on 10 September. Its remit includes examining whether the CoC management should have done more earlier to prevent Letby killing babies on its neonatal unit. The letter makes two proposals. The first is a temporary pause in the public inquiry “to allow for further investigation and to hear wider professional concerns”. The second is to change its terms of reference to enable “a broader examination of potential factors contributing to the increased neonatal deaths, without the presumption of criminal intent”. The lead signatories of the letter are Dr Svilena Dimitrova, a specialist neonatal adviser to the Care Quality Commission and member of the independent Ockenden review into mother and baby deaths at Nottingham university hospitals, and Peter Elston, a fellow of the Royal Statistical Society, who questioned the analysis of shift data on which the prosecution depended before the trial began in October 2022. The letter adds: “We emphasise that our goal is not to relitigate the Letby case, but to ensure that the Thirlwall inquiry is positioned to conduct the most thorough and beneficial investigation possible for the future of neonatal care in the UK.” Other signatories include Prof Peter Green, a former president of the Royal Statistical Society; Dr Neela Shabde, a consultant paediatrician and former clinical director of child health for north-east England; Jenny Harris, an experienced neonatal intensive care nurse; and Prof Stephen Senn, formerly the head of health statistics at the University of Glasgow. The letter says there were a further seven neonatal and paediatric consultants, two advanced neonatal nurse practitioners, and two neonatal nurses who shared their concerns but wished to remain anonymous over fears of repercussions. The intervention comes as fresh questions have been raised about the accuracy of the evidence presented at Letby’s trials. The Crown Prosecution Service confirmed last week that door swipe data from the CoC hospital, relied on by the prosecution to show that Letby had been alone when babies collapsed, was incorrect. Police had wrongly thought that the swipe data showed nurses leaving the neonatal unit and going into the labour ward, when in fact they were returning to the neonatal unit. In Letby’s retrial for the attempted murder of Baby K the prosecution corrected the error, undermining their original assertion that Letby had been alone for one incident, when in fact another nurse on duty in the same room as Letby had returned. The CPS has declined to comment on the swipe data in the first trial. A government spokesperson said the inquiry would provide opportunities to learn from events at CoC: “This was a horrendous case and there were clear failings across the NHS and with regulators. The inquiry will review all aspects of the case and the terms of reference were agreed following wide-ranging engagement with its chair, the families affected and other stakeholders including NHS England.” A spokesperson for the inquiry said hearings would begin as planned on 10 September, and “will follow the terms of reference set by the secretary of state”.