Lucy Letby

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.
Lucy Letby was born on 4 January 1990 in Hereford, the only child of a finance manager and an accounts clerk. She was educated at Aylestone School and Hereford Sixth Form College. A friend who knew her since secondary school told the BBC, "She'd had a difficult birth herself, and she was very grateful for being alive to the nurses who would have helped save her life". This, the friend states, had led her to want to be a nurse all her life.
Letby received her education in nursing at the University of Chester, where she also worked as a student nurse during her three years of training, carrying out placements at Liverpool Women's Hospital and the Countess of Chester Hospital. Letby initially failed her final year student placement, but passed a retrieval placement after requesting a new assessor. In 2011, Nicola Lightfoot, her assessor, reported she was lacking in clinical and medication knowledge and needed more experience in "picking up on non-verbal signs of anxiety/distress from parents"; in a 2024 inquiry, Lightfoot said she had found Letby to be "cold". Letby was the first member of her family to study at university and graduated with a Bachelor of Science in Nursing with a speciality in child nursing in September 2011. She completed a placement course at the Liverpool Women's Hospital by December 2011.
Letby got an appointment as a registered nurse at the Countess of Chester Hospital and started working in the neonatal unit from 2 January 2012. She lived a normal life living in several rented apartments until she bought a house near the hospital, a 20-minute walking distance from her ward, in 2016. In a 2013 staff profile, she said that she was responsible for "caring for a wide range of babies requiring various levels of support" and that she enjoyed "seeing them progress and supporting their families." Letby also took part in a campaign to raise funds for a new neonatal unit at the hospital. She told others that she found non-intensive care work "boring".
Letby completed a specialisation course in neonatal caring in March 2014. She went for another training placements at Liverpool Women's Hospital in early 2015, and qualified to work with infants in intensive care. Her time there came under investigation after her conviction.
In July 2013, Letby and a more senior nurse set the infusion rate for a newborn's morphine at 10 times the correct amount, leading to a suspension from administering controlled drugs by the unit's deputy ward manager. Letby, who was upset by the decision, was required to undergo extra training. Her suspension was lifted a week later, after she complained to the unit manager, who had been on leave during the incident. Letby told colleagues the suspension was an over-escalation, which the deputy ward manager disputed. In 2015, she qualified to work with infants in intensive care, and in April 2016, she administered antibiotics to an infant that was not prescribed them, which she misclassified as a "minor error". She was reassigned by the ward manager from night shifts to day shifts.
In June 2016, Stephen Brearey, lead neonatologist, asked management to remove Letby from clinical duties pending an investigation into her conduct. Letby was transferred to the patient experience team in July 2016 and later to the risk and patient safety office, working there until her arrest in 2018.
In June 2015, four collapses occurred in the same neonatology unit of Countess of Chester Hospital, three leading to infant deaths. The unit typically saw only two or three deaths a year. Eirian Powell, the unit manager, and Stephen Brearey conducted an informal review, and reported the incidents to the committee of the NHS Foundation Trust responsible for addressing serious incidents. Upon review, the committee classed the deaths as medication errors. Brearey observed that Letby had been on shift for all of the incidents, but considered it an unsurprising coincidence; there was only one other qualified junior nurse in the unit, and Letby often worked extra shifts to cover for staffing shortages. He stated, "Nobody had any concerns about her practice." In 2023, reports from The Guardian and The Times stated he was suspicious of Letby beginning in 2015 and accused the hospital of negligence for ignoring his concerns.
During a hospital visit in February 2016, the Care Quality Commission (CQC) was informed of difficulties in raising concerns with managers, but heard no mention of an elevated mortality rate. The CQC's report identified issues of "short-staffing" and "skill-mix" issues within the unit, yet it praised the overall positive culture of the trust, where "[s]taff felt well supported, able to raise concerns and develop professionally." In May 2016, the executive team deemed the spike in deaths to be coincidental and no substantial action was taken. Reports by the nationwide MBRRACE-UK project found a neonatal death rate at least 10% higher than expected between June 2015 and June 2016. Additionally, the neonatal death total in 2015 doubled that of the previous year. Stephen Brearey phoned the duty executive on 24 June 2016, following two more deaths shortly after Letby returned from a holiday in Ibiza, demanding that she be removed from the unit. The duty executive insisted that Letby was safe to work. The Trust's executive directors convened at the end of June and discussed involving the police, but decided against it. The medical director and chief executive instead organised a review through the Royal College of Paediatrics and Child Health (RCPCH). Letby was removed from the unit, working her last shift there on June 30. The unit's services were scaled back by hospital managers on 7 July 2016, cutting cot space numbers and increasing the gestational age limit for admission from a minimum of 27 to 32 weeks.
The RCPCH was tasked with a general review of the unit's service, which was initiated in September 2016. In October 2016, they reported they could not find a definitive explanation for the increase in mortality rate at the unit, but found insufficient staffing and senior cover. They praised Letby's nursing skills and argued that the concerns about her came from a "subjective view with no other evidence". The medical director asked neonatologist Jane Hawdon from Great Ormond Street Hospital to carry out detailed case reviews recommended by the RCPCH, but Hawdon said she did not have the time and instead did a brief review of the medical notes relating to 17 deaths and other incidents and produced a five-page report. She concluded that 13 of the incidents could be explained and "may have been prevented with different care", while the remaining four could "potentially benefit from local forensic review as to circumstances, personnel etc". Records of the hospital board meeting show the medical director telling board members that the RCPCH and Hawdon reviews concluded that the deaths in the neonatal unit were due to issues with leadership and timely intervention. The chair later said he had been misled about the depth of the Hawdon review and its findings.
In September 2016, Letby raised a formal grievance about her late June 2016 transfer from clinical duties to the hospital's risk and patient safety office. This grievance was upheld by the board in January 2017, which determined her removal had been "orchestrated by the consultants with no hard evidence". The medical director commented in the report that the trust's intention was to "protect Lucy Letby from these allegations". The chief executive had met with Letby and her parents on 22 December 2016 to apologise on behalf of the trust and assure them that the doctors who made the allegations would be "dealt with". He later ordered the consultants to send a letter of apology to Letby, which they did in February 2017.
In March 2017, four consultants, including Stephen Brearey and Ravi Jayaram, asked management to involve the police after receiving advice for further investigation from the regional neonatal lead. They then met with Cheshire Constabulary on 27 April 2017, to raise their concerns, with Letby due to return to work on 3 May 2017. Brearey and Jayaram told the Cheshire Constabulary that infant collapses are "nearly always explainable". In May 2024, staff writer Rachel Aviv for The New Yorker reported that a study of infant deaths in southeast London, published in the Journal of Maternal-Fetal and Neonatal Medicine, found that about half of unexpected infant collapses remain unexplained after an autopsy.
The trust publicly announced the involvement of the police in May 2017, stating this move was to "seek assurances that enable us to rule out unnatural causes of death." The investigation, designated Operation Hummingbird, lasted a year. Senior Investigating Officer Paul Hughes later said: "the initial focus was around the hypotheses of what could have occurred: so generic hypotheses of 'it could be natural-occurring deaths', 'it could be natural-occurring collapses', 'it could be an organic reason', 'it could be a virus', and then one of the hypotheses was that, obviously, it could be inflicted harm."
Reading about the investigation in the news, Dewi Evans, a retired paediatrician and professional expert witness, contacted the National Crime Agency in May 2017 via email; he is quoted as writing “Incidentally I’ve read about the high rate of babies in Chester and that the police are investigating. ... Do they have a paediatric/neonatal contact? I was involved in neonatal medicine for 30 years including leading the intensive care set-up in Swansea. I’ve also prepared numerous neonatal cases where clinical negligence was alleged. ... If the Chester police had no-one in mind I’d be interested to help. Sounds like my kind of case.”
During the police investigation which followed, Evans was instructed to review clinical records of the babies in the unit who had died or collapsed suddenly, in total 61 cases. Evans produced a large number of reports for Cheshire Police including a general statement dated 17 April 2019, a review of published literature regarding air embolus in newborn infants dated 3 July 2019 and a series of reports "considering" the events surrounding the deaths or collapses of babies. Letby's trial opened on 10 October 2022 and Evans also remained lead expert witness during the trial. Evans' conclusions were peer reviewed by Dr Sandie Bohin, a practising consultant neonatologist from Guernsey. Evans advised the police on the instruction of experts from specific specialisations, including:
Initially 61 cases of sudden infant collapse or death at the Letby's ward were investigated by Dewi Evans, but this was narrowed down to a total of 22 counts during the trial.
On 3 July 2018, police arrested Letby on suspicion of eight counts of murder and six counts of attempted murder. After Letby's arrest, police began investigating her entire career, including her time at Liverpool Women's Hospital. Letby was bailed on 6 July 2018, rearrested on 10 June 2019, and bailed again on 13 June. On 10 November 2020, she was arrested once again and denied bail. Letby denied all charges against her, and pointed to issues of hospital hygiene and staffing levels.
Letby's trial began at Manchester Crown Court on 10 October 2022 before Mr Justice Goss. She pleaded not guilty to seven counts of murder and 15 counts of attempted murder. Letby's parents and the families of the victims attended the trial.
The neonatal victims were referred to as Baby A to Baby Q which the jury were asked to consider in 22 counts. The press secrecy around the identities of the 17 babies and nine colleagues who gave evidence was "rarely seen outside proceedings involving matters of national security." Two years before the criminal trial, Mrs Justice Steyn banned the identification of the living victims until their 18th birthdays. Several adult witnesses requested anonymity, which is rarely granted, unless testifying would endanger their lives. The judge approved these requests, ruling that getting testimony from the colleagues was more important than them being publicly identifiable.
The mother of Baby E described hearing her infant scream, and walking in to find him with blood around his mouth and Letby in the room. She testified that Letby had attributed the blood to a nasogastric tube, saying "trust me, I'm a nurse." The baby's condition soon worsened and he died a few hours later.
Letby later sent a sympathy card to the parents on the day of the baby's funeral. Upon Letby's arrest it was found on her phone that she had photographed the card before she sent it and had still kept pictures of it. It was also revealed during the trial that Letby had to be told more than once not to enter a room where the parents of one of the victims were grieving. Letby told a colleague that taking Child A to the mortuary was "the hardest thing she ever had to do".
The Crown Prosecution Service cited texts sent by Letby to friends, describing them as a "live blogging" of events and as displaying "intrusive curiosity." Three days after the death of Baby A, Letby had messaged the manager of the unit offering to do more shifts, saying "from a confidence point of view I need to take an ITU baby soon X". Two days later she had a heated text exchange with a colleague over her manager not assigning her to the intensive care room. Shortly after the exchange, Baby C's condition worsened and he died the following day. After the third baby death in a fortnight 2015, Letby replied to a text from a sympathetic colleague saying that she would "keep ploughing on" and added "I think there is an element of fate involved. There is a reason for everything". About two hours after the collapse of Baby M, Letby sent texts reading: "Work has been shit but... I have just won £135 on Grand National!! [horse emoji]." and "Unpacking party sounds good to me with my flavoured vodka ha ha." Letby had also searched for the families of several infant victims on Facebook, including on the anniversaries of their babies' deaths and on Christmas Day. The prosecution said that she would search for a number of them within minutes of each other, as if "hunting for grief". In total Letby had searched for 11 of the families affected. Letby testified that this was out of "general curiosity" and said, "I was always on my phone". She searched for the families of infants 31 times; during the year the deaths took place, she searched for other people 2,287 times.
The prosecution in Letby's case argued that suspicious incidents began in 2015, when Letby qualified to work with infants in intensive care, and that in April 2016, when the ward manager reassigned Letby from night shifts to day shifts, their distribution shifted accordingly.
A consultant testified that, in February 2016, he had walked in on Letby standing over a desaturating infant and failing to intervene. He said that Letby had responded to his questions by telling him that the infant had only just started declining. The infant in question survived the collapse.
Between March and June 2016 another three babies almost died while under Letby's care. Towards the end of June, she was helping care for triplets. Consultants said that they had been in good health and the deaths of two boys on consecutive days were causing staff considerable distress and shock.
In August 2015, one infant (referred to as Baby E) died and within hours his twin (Baby F) became seriously unwell but fully recovered later the same day. During the police investigation, a doctor helping police look over clinical records noticed unusual blood test results for Baby F and one other infant (Baby L). A third blood test result with similar characteristics was later discovered in the clinical records by the prosecution's lead expert witness. The first two of these test results resulted in attempted murder charges and became central to the trial, but Letby was never charged in relation to the third. The prosecution argued that the test results demonstrated deliberate poisoning by insulin. Their lead expert witness described this evidence as the "smoking gun". Since the trial, this interpretation of the blood test results has been disputed by experts (see: § Concerns about the medical evidence).
At the same time as Baby L's blood sugar collapse, his twin brother, Baby M, unexpectedly collapsed while under Letby's care but managed to survive after thirty minutes of resuscitation. The prosecution argued that Letby had injected air into his bloodstream. The prosecution also noted that, although by this point she was not supposed to work night shifts, Letby was caring for Baby L as she specifically volunteered to do an extra shift to care for her.
A paediatrician testified that he and other clinicians had previously raised concerns about Letby, but were told by hospital administration that they "should not really be saying such things" and "not to make a fuss." Another doctor testified that Letby commented an hour before one victim died, "He's not leaving here alive, is he?" The doctor replied 'don't say that' and left the ward overruling Letby's objection. Letby's trial testimony is consistent with the doctor returning to the ward after a cigarette. Although the consultants made their desire to have Letby removed from duties known to hospital staff after the triplet incident, this was refused and the next day another baby almost died under Letby's care.
The prosecution presented the jury with a shift chart showing Letby as the only nurse on duty for 25 incidents, which included swipe data to show Letby's movements around the unit (see: § Mislabelled door swipe data). Referring to the chart in his opening remarks, prosecuting barrister Nick Johnson said, "by a process of simple elimination" Letby must be responsible for the incidents. Since the trial, statisticians and others have questioned the use of this chart (see: § Quality of the statistical evidence) and the criteria by which incidents were included on it or not. After her removal from duty, and the downgrade of the unit to no longer admit infants requiring intensive care or those born before 32 weeks, the unexpected deaths stopped. Letby was accused of falsifying times on patient records so as not to be placed at the scene of the collapse. She denied doing so and suggested the changes were errors made by her or another nurse. Criminal psychologist David Holmes has argued that the varied methods she was said to have used to attack the infants, such as insulin and air injections and overfeeding milk, would all have been specifically chosen as things that would dissipate and not be easily detected afterwards.
Searches of Letby's and her parents' homes, and Letby's handbag, revealed post-it notes handwritten by Letby. These included fragmentary phrases such as "help", "I'm sorry that you couldn't have a chance at life", "I don't want to do this anymore", "not good enough", "why me?", "I haven't done anything wrong", "we tried our best and it wasn't enough", "I am evil, I did this", and "I killed them on purpose because I'm not good enough to care for them". Another document that was presented said "I don't know if I killed them. Maybe I did. Maybe this is all down to me".
The defence argued that the notes were "the anguished outpouring of a young woman in fear and despair", written while Letby was dealing with employment issues including a grievance procedure with the NHS Trust. The prosecution said that the notes expressed Letby's frustration at being removed from the neonatal unit. Since the trial, criminology experts have contested the prosecution’s interpretation of the notes (see: § Interpretation of handwritten notes). Letby denied that the notes were a confession, describing them as a reflection of her mental turmoil, written while she was being investigated. The Guardian, in its reporting after the verdict, described the notes as "[t]he closest the prosecution had to a confession"; they later reported that the notes had been written on the advice of Letby's GP to help her process the extreme stress of being investigated.
Letby's diary was also found to be marked with the initials of the dead babies. Initials of those who had died were found to have been marked on the dates they were born, the days the prosecution alleged she attacked them, and on the days that they died.
Searches of Letby's home found sensitive medical documents under her bed, including nursing handover sheets, resuscitation records, and blood gas readings. Of the 257 sheets, 21 related to infants Letby had allegedly harmed. Letby testified that she "collect[ed] paper" and had forgotten to remove the sheets from her pockets at the hospital; she also claimed that she could not destroy them, but a paper shredder was found in her home.
Letby herself gave evidence to the court in May 2023. When questioned by her defence barrister, she became tearful claiming she was made to feel as though she were incompetent but "meant no harm." Letby said that the allegations had negatively impacted her mental health, saying, "I don't think you can be accused of anything worse than that. I just changed as a person, my mental health deteriorated, I felt isolated from my friends on the unit." It was also noted that she repeatedly contradicted herself, muddled up her story and became more and more frustrated with the prosecution's questions, which was unlike her usual calm demeanour.
Letby's defence lawyer said that Letby was "a dedicated nurse in a system which has failed", that the prosecution's case was "driven by the assumption that someone was doing deliberate harm combined with the coincidence on certain occasions of Miss Letby's presence", and that there had been a "massive failure of care in a busy hospital neonatal unit – far too great to blame on one person". The defence argued that "extraordinary bleeding" in one infant could have been caused by a rigid wire or tube.
The defence argued that the evidence presented by the prosecution was insufficient to justify their theories of how the infants were harmed. They argued that the evidence suggesting air embolism was so weak that there was "no case to answer". Defence barrister Benjamin Myers pointed out that "air embolism" made no appearance in Letby's internet search history. However, they did not call any medical experts of their own to the witness box.
The only defence witness other than Letby herself was a plumber who testified that plumbing issues at the hospital led to sewage washing up into the sinks on the unit. He told the jury that issues like this at the hospital led to him being called out "maybe weekly". The defence argued that these hygiene issues could contribute to explaining the unit's high mortality rate. In a November 2024 interview by John Sweeney, Dewi Evans acknowledged the known presence of pseudomonas in the neonatal unit's water supplies, leading to several cases of pneumonia.
Letby's defence attempted to argue no case to answer on the grounds that:
Justice James Goss ruled that there was "a sufficient body of accepted expert medical opinion that administration of air into the venous system could cause air embolism which might be fatal".
Final verdicts were returned by the jury on 18 August 2023. Letby was found guilty of seven counts of murder of seven babies, making her the most prolific child killer in modern UK history.
Letby was also found guilty of seven counts of attempted murder of six infants. Letby was found not guilty on two counts of attempted murder. The jury was unable to reach verdicts on six further attempted murder charges. Nicholas Johnson KC asked the court for 28 days to consider whether a retrial would be sought for these six counts.
The jury acquitted Letby of the attempted murder counts 9 (Baby G) and 10 (Baby H) and could not reach a verdict on counts 11 (Baby H), 13 (Baby J), 14, (Baby K), 18 and 19 (Baby N) and 22 (Baby Q).
On 21 August 2023, Letby was sentenced to life imprisonment with a whole life order, the most severe sentence possible under English law; she is the fourth woman in UK legal history to receive such a sentence. Goss said that Letby committed "a cruel, calculated and cynical campaign of child murder involving the smallest and most vulnerable of children." In closing, he stated, "there was a deep malevolence bordering on sadism [...] you [Letby] have no remorse [...] there are no mitigating factors [...] the offences are of sufficient severity to require a whole life order."
Letby opted not to attend the sentencing hearing and as such heard neither the various victim impact statements which were read out, nor her sentence being passed. In response, Alex Chalk, Secretary of State for Justice, wrote that the government will "look at options to change the law at the earliest opportunity" to compel defendants to attend their sentencing. On 30 August 2023, Prime Minister Rishi Sunak announced that the UK government would introduce legislation to Parliament that would compel convicted criminals to attend their sentencing hearings, by force if necessary, or face the prospect of more time in prison. This was proposed as a new clause to the criminal justice bill in a 2024 parliamentary debate.
After the trial, Letby was transferred to HMP Low Newton, a closed prison for women in County Durham. As of January 2024, Letby is being held in HM Prison Bronzefield.
No motive was upheld by the court, though it is not required for a finding of guilty. The prosecution in Letby's case suggested several theories including boredom, thrill-seeking, and "playing God" as possible motives. They also alleged that Letby had a secret relationship with a married doctor involved with some of the cases. As evidence, they cited Letby's frequent texts to him on certain night shifts, as well as a piece of paper from Letby's office where she had written phrases including, "I trusted you with everything and loved you", "you were my best friend" and "please help me". Letby denied all these suggestions, including the idea that she had a relationship with, or crush on, the doctor in question.
The former detective who acted as lead investigator on the 1990s Beverley Allitt case drew parallels between Allitt's and Letby's cases, suggesting that Letby might have copied Allitt's methods. Criminal psychologists Dominic Wilmott and David Holmes suggested that Letby may have been motivated by factitious disorder imposed on another, a theory also proposed about Allitt.
David Wilson, an emeritus professor of criminology, published an August 2023 opinion piece in The Guardian argued that Letby was driven by a "hero complex". Later that month, Wilson discussed Letby on Newsnight, where he argued that healthcare killers join the profession in order to target vulnerable victims, such as the very old or very young.
On 13 March 2020, while out on bail, Letby was placed on an interim suspension by the Nursing and Midwifery Council. On 18 August 2023, Andrea Sutcliffe, Chief Executive and Registrar of the Nursing and Midwifery Council, stated that Letby "remains suspended from our register, and we will now move forward with our regulatory action, seeking to strike her off the register". Letby was removed from the nursing register on 12 December 2023, having informed the Nursing and Midwifery Council that she did not accept guilt but did not contest the removal.
In January 2024, Letby applied to the Court of Appeal for permission to appeal her convictions, which a judge refused. Letby renewed her application and at a three-day hearing in April 2024 her lawyers put forward four grounds of appeal concerning the trial judge's refusal of applications, but in May 2024 the three judges of the Court of Appeal—Dame Victoria Sharp, Lord Justice Holroyde and Mrs Justice Lambert—refused permission to appeal.
As part of the appeal Letby's counsel Ben Myers again tried to question the inclusion of evidence by Dewi Evans, a doctor and the prosecution's lead witness, saying it should have been disallowed as evidence as he had been "dogmatic and biased". The appeal judges rejected these criticisms, ruling that Evans did not lack impartiality, he was well-qualified to give an opinion, and it was up to the jury to assess the quality of his evidence.
A second ground for appeal was that the medical evidence that Letby had fatally injected air into babies' bloodstreams was "very weak", while the third ground was that the judge had been wrong to direct the jury that they could convict even if they were unsure of the precise method used by Letby for every case. The final ground was that the judge had failed to investigate the impartiality of one of the jurors. All of these four grounds were refused by the Court, with the judges' subsequent written statement concluding that the trial had been "thoughtful, fair, comprehensive and correct" and that none of the four legal challenges advanced by Letby were "arguable", saying that the criteria for the admission of fresh evidence had not been met.
At a hearing on 25 September 2023, the CPS confirmed that there would be a retrial on one of the six counts of attempted murder against Letby on which the jury at the original trial could not reach a verdict. This was not to start until after judges had decided whether or not to grant Letby permission to appeal against her existing convictions.
The retrial started on 10 June 2024. On 2 July, Letby was found guilty of attempted murder, and on 5 July 2024 was sentenced to another whole-life order.
On 24 October 2024, Letby applied for permission to appeal against this conviction on the grounds that prejudicial media coverage should have prevented the trial from proceeding. The Court of Appeal rejected Letby's application.
Following the verdict, it was reported that police were investigating whether Letby harmed other babies. There was a continuing investigation of incidents which detectives had identified as "suspicious" at the Countess of Chester Hospital involving around 30 other infants. Neonatologists looked into about 4,000 admissions at the hospital and Liverpool Women's Hospital, where Letby had worked from 2012 to 2015, and were to pass on any cases of "unexpected and unexplained" deteriorations to police. At least one family was told by police that the birth of their child at the latter hospital was part of the enquiry. Cheshire Police have said that further charges could "possibly" be brought against Letby as a result of these further investigations. They have interviewed Letby under caution about deaths at two hospitals.
On 4 October 2023, Cheshire Constabulary announced an investigation into corporate manslaughter at the Countess of Chester Hospital.
After Letby's conviction the British government ordered an independent inquiry into the circumstances surrounding the deaths and other incidents. The Department of Health and Social Care said the inquiry would examine "the circumstances surrounding the deaths and incidents, including how concerns raised by clinicians were dealt with." It was affirmed that the inquiry would be non-statutory, so witnesses could not be compelled to give evidence and inquests would still be necessary. The trust's medical director, chief executive and the nursing director at the time of the incidents all commented they would fully cooperate with the inquiry. The medical director retired in August 2018 and the chief executive resigned in September 2018 after signing a non-disclosure agreement.
Slater and Gordon, a law firm representing two of the victims' families, issued a statement calling for the inquiry to have the power to compel witnesses to participate, since a non-statutory hearing "must rely on the goodwill of those involved to share their testimony." The need for a statutory inquiry was a view echoed by, among others, Sir Robert Buckland, former Secretary of State for Justice, Samantha Dixon, MP for the City of Chester, Steve Brine, chair of the House of Commons Health and Social Care Select Committee, Sir Keir Starmer, Leader of the Opposition, and the Parliamentary and Health Service Ombudsman.
In August 2024, a group of 24 neonatal and statistical experts wrote a letter to ministers requesting that the inquiry be postponed and its terms changed, in response to concerns about the safety of Letby's convictions (see: § Safety of the convictions). The inquiry rejected these suggestions.
The education minister Gillian Keegan said that the type of inquiry would be reviewed after the chair was appointed. On 30 August 2023, Health Secretary Steve Barclay announced that the inquiry had been upgraded to a statutory inquiry, describing it as the best way forward and meaning that witnesses would be compelled to give evidence.
Lady Justice Thirlwall was appointed to chair the inquiry. The terms of reference of the inquiry were published on 19 October 2023 and updated on 22 November 2023, when she formally opened the inquiry.
The public inquiry began on 10 September 2024. Following submissions, the Chair had ruled on 29 May 2024 that remote live viewing would be available to the Core Participants, their legal representatives and the media but that livestreaming "to the world at large" would not. Colleagues testified that Letby was "excited and gossipy" while discussing the death of an infant, always wanted to handle babies who were "unwell", shouted when she was removed from the intensive care unit stating Letby felt that caring after healthier babies "was boring looking after the special care babies", and that she couldn't wait for the first death of an infant to "get it out of the way".
Former Health Secretary, Jeremy Hunt, apologised to families of the victims during the 2025 hearing for taking "too long" to act.
Lawyers for Letby and other supporters of her called for the inquiry to be paused while her appeal to the Criminal Cases Review Commission is considered. Thirlwall rejected this request in March 2025 and says she plans to deliver her report in November 2025.
In September 2024, Letby appointed a new defence lawyer, Mark McDonald. At a press conference in December 2024, McDonald announced that he was preparing new applications to both the Court of Appeal and the Criminal Cases Review Commission. He argued that the prosecution's lead expert witness, Dewi Evans, was unreliable, as Evans had changed his mind about how some infants had died. McDonald also said that several experts were working unpaid on reports into the infants’ deaths and episodes, with two reports, on Child C and Child O, already completed and finding no deliberate harm.
Following the press conference, Evans denied changing his mind and described McDonald's criticisms as "unsubstantiated, unfounded, inaccurate". He said that the date of Child C's death was the only change in his evidence and that this was the result of a simple error by the prosecution. His post-trial comments about the mode of death of some infants contradict positions he took as a witness at the trial.
On 4 February 2025, Lucy Letby's legal team applied for her case to be reviewed as a potential miscarriage of justice. Coinciding with this application, findings from a panel of 14 international medical experts were released. The panel was chaired by Shoo Lee, a retired neonatologist from the University of Toronto. The panel concluded that there was no medical evidence to support claims that Letby deliberately harmed or murdered babies at the Countess of Chester Hospital. Instead, they attributed many of the babies' deaths to natural causes or substandard medical care, highlighting issues such as inadequate staffing and delays in essential treatments. These findings challenged Letby's convictions, concluding that the deaths were due to factors unrelated to any deliberate actions on her part.
The British Medical Association, which represents doctors, called for a process for NHS managers and healthcare administrators to be held accountable for mismanagement, in a similar way to how the General Medical Council may strike off doctors who harm patients. A neonatal consultant who alerted administrators about his suspicions about Letby also called for regulation of healthcare management.
The Parliamentary and Health Service Ombudsman Rob Behrens, called for radical change to NHS management in order to prevent future similar occurrences.
Dewi Evans has called for an investigation into the possibility of charges of corporate manslaughter in relation to the Letby case. NHS England's Chief Nursing Officer Dame Ruth May issued a statement saying, "The NHS is fully committed to doing everything we can to prevent anything like this ever happening again, and we welcome the independent inquiry announced by the Department of Health and Social Care to help ensure we learn every possible lesson from this awful case."
On 21 August 2023, it was announced that the nursing director at the Countess of Chester Hospital at the time Letby was based there had been suspended from her job as a senior nursing officer at Northern Care Alliance NHS Foundation Trust with immediate effect, because of information that came to light during the trial. The Nursing and Midwifery Council subsequently announced she would face an investigation into her fitness to practice. She and other executives at the hospital have been accused of ignoring warnings about Letby.
It was reported that the British government were examining how Letby's pension can be stopped. The NHS pension scheme regulations provide for a forfeit of pensions after a conviction of certain crimes.
Letby has always maintained her innocence and had the support of friends and some former colleagues. Some medical, statistical and scientific experts have also expressed doubts about her convictions. That Letby's defence only called two witnesses at her trial—Letby herself and a plumber—has been taken by some to suggest that the jury did not get a fair opportunity to hear a balanced view of the evidence. Since the conclusion of her second trial in July 2024 and the lifting of associated reporting restrictions, some of these concerns have been published in the press. The Appeal Court has rejected several arguments around the safety of the convictions.
Much of the medical evidence used in the trial has come under criticism from experts across a range of specialties, including neonatology, pathology, nursing, biochemistry, forensic toxicology, and others. Under scrutiny have been the prosecution’s claims that the infants were stable before the incidents, that other explanations could be ruled out, and that the alleged methods of attack were plausible. The overturning of the original pathologists' reports into the infants' deaths has drawn controversy; the majority of the infants Letby was convicted of murdering had undergone autopsies, and none of the original pathologists' reports had suspected an unnatural death.
In February 2025, a panel of 14 international experts, convened by neonatologist Shoo Lee, presented findings from their own investigation into the deaths and collapses (see: § Expert panel investigation). They concluded that all the incidents could be explained by natural causes and/or substandard care, finding no evidence of deliberate harm.
The following sub-sections highlight some of the concerns raised prior to this expert panel's investigation as well as some from the information currently publicly available about the findings from the panel (hereafter 'the Lee panel').
Experts have questioned the interpretation of blood test results used as evidence that Letby poisoned two infants with insulin. Several have argued that the type of test used is too prone to error to be used in a criminal trial. A guidance note from the laboratory that carried out the tests recommends confirmatory analysis with a more accurate test if insulin administration is suspected, but no further testing was done in these cases. Others have suggested that, if accurate, the results have alternative possible explanations. Professor Joseph Wolfsdorf, a specialist in child hypoglaecemia at Harvard Medical School, has questioned whether the results for one infant were even consistent with insulin poisoning. And Professor Geoff Chase, a specialist in insulin in pre-term infants, has studied the cases with chemical engineer Helen Shannon; they concluded that the prosecution’s experts greatly underestimated the amount of insulin Letby would have had to use. No evidence was presented at trial that any had gone missing from the unit.
Chase and Shannon later examined the infants’ records as part of the Lee panel. They argued that, in addition to issues with the reliability of the test, the pattern of results could not be taken to indicate insulin administration in pre-term infants, whose physiology is different from that of older children or adults.
Several neonatologists have described the claim that Letby murdered three infants by injecting air into their stomachs via a nasogastric tube variously as "nonsensical or 'rubbish', 'ridiculous', 'implausible' […] 'fantastical'" and "not practically feasible".
An X-ray heavily discussed by the prosecution was used to argue that Letby had killed Child C by this method, but she had not been on shift since the child's birth when it was taken. Shortly after the broadcast of a BBC File on 4 programme that discussed this case, Dewi Evans, who served as the prosecution's lead expert witness, said that he no longer agrees with the prosecution's account of how the infant died, but instead said that Letby had killed him via another method. He has said he no longer believes that any of the infants were killed "as a direct result" of air injected into their stomachs.
The Lee panel concluded there was no evidence that air had been forced down any of the infants' nasogastric tubes.
The prosecution used a 1989 study by Shoo Lee and A. K. Tanswell to argue that discolourations observed on the skin of some of the infants were diagnostic of air embolism. After the trial, upon reviewing the descriptions of the infants' skin discolourations, Lee, a prominent neonatologist, disagreed that they are suggestive of air embolism. Lee also described any attempt to diagnose air embolism just by ruling out other possibilities as "a fundamental mistake of medicine." The defence applied to use Lee as a witness for an appeal in 2024, but the Court of Appeal ruled that his testimony was not admissible since he could have been called at the trial and the prosecution's case did not solely rely on skin discolouration to indicate the condition.
Since this appeal attempt, Lee has published an updated version of his 1989 paper, which he argues further undermines the prosecution's case by showing that venous air embolism has never been documented to result in patchy skin discolouration.
Abid Qazi, a former NHS paediatric surgeon whose case report about an infant's death from air embolism was used in a report by the lead prosecution expert witness, has reviewed the case of one of the infants Letby was convicted of murdering by this method and said, "I'm very sceptical about the diagnosis". He continued, "I have been closely following the case of Lucy Letby and I believe she has been a victim of the poor NHS system."
The Lee panel posited alternative causes for the incidents the prosecution alleged were caused by air embolism. They argued there was no evidence of air embolism.
The prosecution argued that liver damage seen at the post-mortem for Child O could only be explained by deliberate harm. This was contrary to the original pathologist's opinion that natural causes explained the damage. A leading senior perinatal pathologist has since reviewed the case and said that she has previously seen liver damage of this kind result from natural causes. She called the prosecution expert's position "naive" and agreed with the original pathologist. Published research reports hundreds of similar cases occurring naturally in neonates. A joint report by two neonatologists working with Letby's legal team argues that Child O's liver was accidentally punctured by a doctor inserting a needle in the wrong place.
The Lee panel argued that the doctor's needle may have penetrated the liver, though the liver injury was initially caused by a traumatic delivery.
Letby was convicted of attempting to kill Child K by dislodging her breathing tube. Experts have questioned how this could be concluded when no witnesses saw the event and accidental dislodgement is "extremely common". The Lee panel argued that there was no evidence the tube had been dislodged, and that the deterioration was instead caused by the tube being too small for the infant.
Several statisticians have criticised the prosecution's use of data. The prosecution have been accused of falling victim to the Texas sharpshooter fallacy and the prosecutor's fallacy. A shift chart shown to the jury, ostensibly placing Letby uniquely at the scene of every suspicious event, has been criticised on the grounds that the criteria for inclusion of incidents were unclear and likely biased, rendering it misleading. Critics highlight, for instance, that some deaths and other incidents were left out. It also excluded non-nursing staff members and did not provide context such as how often each nurse had worked over the period. Others have used data from across the NHS to argue that the cluster of deaths at the unit was not statistically anomalous. Alternative explanations for the spike in mortality have been posited.
During their investigation, Cheshire Police contacted Professor Jane Hutton, an expert in medical statistics, and signed a consultancy agreement with her. However, the Crown Prosecution Service instructed the police to drop this line of inquiry and Hutton's planned analysis never took place. Since the conclusion of the trials, she has been among the experts vocal in criticising the prosecution's case, arguing that the evidence concerning data "does not hold water".
To discuss its members' concerns, in September 2024 the Royal Statistical Society held a meeting at which parts of the prosecution's evidence were harshly criticised and comparisons were made with evidence used in miscarriages of justice involving other nurses who had been convicted of killing their patients (see: Lucia de Berk case and Daniela Poggiali).
In May 2024, The New Yorker published a feature article by staff writer Rachel Aviv that questioned Letby's conviction. Aviv pointed to pervasive staffing shortages, with staff "overtaxed" and only one specialist neonatologist for the ward, and hygiene issues. An inquest had found that an infant had died in 2014 due to doctors inserting a breathing tube incorrectly. As the defence had presented at trial, issues with the unit's drainage system meant that pipes were often blocked, leading to occasional sewage backup in the sinks.
Aviv also highlighted a previous investigation into the increased mortality on the unit that was carried out by the Royal College of Paediatrics and Child Health (RCPCH), and the hospital's response. In September 2016, the RCPCH interviewed staff at the Countess of Chester Hospital. Their subsequent report concluded that medical and nursing staff levels were inadequate. They observed that the 2015 increase in mortality was not limited to the neonatal unit. They described Letby as "enthusiastic, capable and committed" and the staff on the unit as "very upset" about her removal from clinical duties. Of the doctors who suspected her, the report argued that they had a "subjective view with no other evidence". In a public response to the report, the hospital admitted issues with "staffing, competencies, leadership, team working and culture."
Due to reporting restrictions imposed as a result of Letby's impending retrial, the online version of the article was disabled for British readers, a decision which was questioned in Parliament by the Conservative MP David Davis. The issue of The New Yorker's print edition that contained the article was, however, available for sale in British newsagents as usual.
In August 2024, a report was leaked to The Telegraph that showed that the unit on which Letby worked had suffered an outbreak of a dangerous bacteria during the period in which the infants Letby was convicted of murdering died. This outbreak was not mentioned in Letby's trial. Commenting on the leaked report, professor of medical microbiology David Livermore argued that the bacterial outbreak is a simpler explanation for the observed spike in deaths on the unit than that Letby had murdered several infants.
Throughout the first trial, door swipe data was used to establish Letby's presence at the incidents. In August 2024, the Crown Prosecution Service confirmed that during this trial, swipe data for one of the doors to the neonatal unit had been mislabelled such that entries and exits were reversed. They did not confirm whether the data for other doors had been correctly labelled. Cheshire Police reviewed the use of the false data and concluded that it was used in evidence relating to nine infants, but only played a central role in the case of Child K, who Letby was not convicted of harming at the first trial.
There was another door to the unit which did not record entries or exits, meaning door swipe data could not account for all movements in and out.
During the trial, handwritten notes found at Letby's home were presented by the prosecution as amounting to a confession. Faye Skelton, a lecturer and specialist in forensic psychology, has highlighted that the notes also contain phrases that deny her guilt. She told Channel 5 that "they are perfectly plausible as the output of someone who is suffering extreme mental distress. … I do not see the notes as a confession or as an admission of guilt".
In September 2024, The Guardian reported that the notes were written on the advice of counsellors as part of a therapeutic process. Richard Curen, the chair of the Forensic Psychotherapy Society, was quoted saying, "Doodling, journalling is a way of taking control of your thoughts. I don't think it relates to a confession of any kind."
A number of medical experts questioned the veracity of the prosecution's witness Dewi Evans, a professional expert witness. Svilena Dimitrova, an NHS consultant neonatologist, and Roger Norwich, a medico-legal expert, have made official complaints to the General Medical Council about Evans' evidence. Dimitrova told The Guardian that she believes "the theories proposed in court were not plausible and the prosecution was full of medical inaccuracies. I wasn't there, so I can't say Letby was innocent, but I can see no proof of guilt". Evans rejected the suggestion that he was biased and said that the defence at the trial could have called expert witnesses to challenge his opinions but did not do so. At the trial, other prosecution expert witnesses largely endorsed his opinions.
The New Yorker article highlights that a report written by Evans as an expert witness in a previous case had been described by a Court of Appeal judge as "worthless" and including opinions that were "tendentious and partisan" and "outside Dr. Evans' professional competence."
Dewi Evans has said that he has received abuse by Letby's supporters online who doubt the safety of her conviction. Speaking to the BBC about this, he described it as being similar to intimidation received by doctors from supporters of outed abusers in the 1980s and 1990s. He has argued that people find it difficult to accept that a killer could be a "young, white, English nurse from a respectable background" who "hid in plain sight", adding: "It happened with Harold Shipman, it happened with Jimmy Savile, it is crucial to their getting away with it that they appear normal".
A barrister for the infants' families has described the doubts about the convictions as "conspiracies, some of which are grossly offensive and distressing for the families of her victims". The families' barristers called for the Thirlwall Inquiry to be publicly livestreamed, arguing that the doubts are "often ill-informed, and they ultimately grow in the shadows. The more light that we put on this Inquiry, the less space there is for speculation and conspiracy". However, the inquiry was unconvinced of the need to livestream and rejected the application.
BBC special correspondent Judith Moritz, one of only four reporters allowed in the courtroom, told The Sunday Times that the debate over the conviction is missing key aspects the jury saw during the trial. Moritz said she was troubled by Letby's behaviour and lack of emotion about the deaths of the infants, but was "tearful" when discussing herself, the loss of her job, and the correspondence with the married doctor. Letby did sob in court when recounting the death of an infant. Moritz also said that Letby contradicted herself and tried to "out-lawyer" the prosecutor. Observers in the courtroom during her original trial said that Letby was "aloof and indifferent" and claimed she had no recollection of incidents, contributing to the appearance of her guilt.
During Letby's 2022–2023 trial, the prosecution's expert witness Dewi Evans referred to a 1989 article written by Shoo Lee, a Canadian neonatologist, to diagnose air embolism as the mechanism of murder of the babies. Lee, the president of the Canadian Neonatal Foundation, was not called as an expert witness during Letby's trial and, living in Canada, did not hear about the use of his research until after the verdict. Upon learning about the case, he became concerned that his research had been misused. After Letby's unsuccessful application for leave to appeal in 2024, Lee convened a panel of 14 medical experts from six countries to review all of the cases from Letby's trials. They were provided with the medical records and relevant witness testimony by Letby's barrister, but accepted no payment and committed to releasing the findings even if they did not favour Letby.
On 3 February 2025, Lee appeared in a press conference with Letby's barrister, Mark McDonald, the MP, David Davis, and neonatologist and former president of the Royal College of Paediatrics and Child Health, Neena Modi. Lee reported that the panel "did not find any murders" and that "in all cases, death or injury were due to natural causes or just bad medical care." Days later, he called for Letby to be immediately released from prison and placed under house arrest until the case can be retried. In parallel, Letby's legal team applied to the Criminal Cases Review Commission, which deals with potential miscarriages of justice, to review the case.