Lucy Letby (born 4 January 1990) is a British former neonatal nurse who was convicted of the murders of seven infants and the attempted murders of seven others between June 2015 and June 2016. Letby came under investigation following a high number of unexpected infant deaths which occurred at the neonatal unit of the Countess of Chester Hospital three years after she began working there. Letby was charged in November 2020 with seven counts of murder and fifteen counts of attempted murder in relation to seventeen babies. She pleaded not guilty. Prosecution evidence included Letby's presence at a high number of deaths, two abnormal blood test results and skin discolouration interpreted as diagnostics of insulin poisoning and air embolism, inconsistencies in medical records, her removal of nursing handover sheets from the hospital, and her behaviour and communications, including handwritten notes interpreted as a confession. In August 2023, she was found guilty on seven counts each of murder and attempted murder. She was found not guilty on two counts of attempted murder and the jury could not reach a verdict on the remaining six counts. An attempted murder charge on which the jury failed to find a verdict was retried in July 2024; she pleaded not guilty and was convicted. Letby was sentenced to life imprisonment with a whole life order. Management at the Countess of Chester Hospital were criticised for ignoring warnings about Letby. The British government commissioned an independent statutory inquiry into the circumstances surrounding the deaths, which began its hearings in September 2024. Letby has remained under investigation for further cases. Since the conclusion of her trials and the lifting of reporting restrictions, various experts have expressed doubts about the validity of her convictions due to contention over medical and statistical evidence, technical errors, and the lack of a clear motive. Medical professionals contested the interpreted diagnostics as "not sufficient" for criminal evidentiary use and "implausible", arguing the autopsies indicated the infants had died of natural causes. Two applications for permission to appeal have been rejected by the Court of Appeal. An application to the Criminal Cases Review Commission and a new application to the Court of Appeal are pending.