Lucy Letby Case: Netflix Documentary Fuels Doubt Over Conviction of ‘Most Prolific’ Female Serial Killer
A new Netflix documentary, The Investigation of Lucy Letby, is challenging the 2023 conviction of neonatal nurse Lucy Letby, who was found guilty of murdering seven babies and attempting to murder seven more, making her one of the United Kingdom’s most notorious criminals. While initially hailed as a case closed – a chilling example of a calculated serial killer – the documentary raises serious questions about the evidence and the investigation, suggesting a potential miscarriage of justice.
Letby, born January 4, 1990, pursued a career in nursing, earning a BSc in Child Nursing from the University of Chester. She began working at the Countess of Chester Hospital in Northern England after completing her university placement there, quickly becoming a fixture in the neonatal department. “There was nothing about her that made her stand out to me,” recalled Dr. John Gibbs, a retired consultant pediatrician, in the documentary.
However, beginning in June 2015, a disturbing pattern emerged at the hospital: a series of unexplained infant deaths. One baby, identified as Zoe (her name changed for the documentary), tragically died after initially responding well to treatment. Her mother, anonymized in the film, recounted a challenging birth followed by a brief period of hope before her daughter’s sudden collapse on June 22. Three other babies died at the Countess of Chester on June 8, 14, and 22, 2015, escalating concerns among staff. By February 2016, the death toll reached nine, and by the following June, thirteen. “In the 21 years I’d been a consultant, I’d never seen anything like this before,” Gibbs stated.
An investigation revealed a troubling correlation: Letby was the only nurse on duty during every suspicious death in the neonatal unit. Despite initial assurances of her competence from unit management, Letby was eventually moved from night shifts to day shifts. The documentary alleges that the number of collapses and deaths decreased during the night, only to resume during the day, fueling suspicions.
Letby’s arrest came on July 3, 2018, following a search of her home. Police discovered a collection of over 250 confidential handover sheets and documents pertaining to the babies involved, meticulously arranged in chronological order. She claimed she had taken the documents home accidentally. Following two releases on bail, Letby was arrested a third time on November 10, 2020, and subsequently charged with eight counts of murder and ten counts of attempted murder. She spent 23 months in custody awaiting trial.
The prosecution, beginning October 10, 2022, presented evidence suggesting Letby intentionally harmed infants, alleging she removed airway tubes or overfed them, restricting their breathing. The case against Letby centered on circumstantial evidence, including a strange skin discoloration observed in Baby Zoe, and the presence of air in her bloodstream – an air embolism. Medical examiner Dr. Evans testified that the embolism was caused by a deliberate injection of air into the intravenous system. Prosecutors also highlighted Letby’s online activity, noting she searched for the parents of deceased babies on Facebook, and that she messaged colleagues about the deaths. The discovery of insulin administered to two babies who did not require it was described as a key piece of evidence. Furthermore, post-it notes found at Letby’s home bearing phrases like “I killed them,” “I am evil,” and “I did this” were presented as damning evidence. “Objectively, it couldn’t have been anyone else,” asserted Simon Blackwell, Detective Superintendent, Cheshire Police. Despite maintaining her innocence and pleading not guilty, Letby was convicted on August 18, 2023, and sentenced to life in prison.
However, the narrative began to shift with the release of The Investigation of Lucy Letby. Mark McDonald, a criminal defense barrister now representing Letby, argues there was no concrete motive, no CCTV footage, and no direct witnesses to any wrongdoing. He contends the post-it notes, while disturbing, may reflect a therapeutic exercise suggested to Letby, and that phrases like “slander” and “discrimination” suggest she didn’t believe she was responsible. A 2024 article in The New Yorker by Rachel Aviv further questioned the verdict, suggesting systemic issues within the hospital itself may have contributed to the deaths.
McDonald points out that Letby, being more qualified than many of her colleagues, was assigned the most critically ill infants. “It would be odd if she wasn’t there when something went wrong,” he stated. He also argues that the decline in mortality rates after Letby was removed from the unit is misleading, as the unit itself was downgraded, receiving fewer seriously ill babies. “The mortality rates were always going to drop,” he explained.
The campaign for Letby’s freedom has gained momentum, attracting support from figures like Sir David Davis, a sitting UK member of parliament, who has labeled the trial a “clear miscarriage of justice.” Much of the renewed scrutiny focuses on the testimony of Dr. Evans, the medical examiner. McDonald revealed that a senior judge, uninvolved in the trial, alerted the trial judge to concerns about Evans’ impartiality, stating he “makes no effort to provide a balanced opinion” and “no attempt has been made to engage with the full range of medical information.”
To challenge the validity of Evans’ conclusions, McDonald contacted Professor Shoo Lee, the original author of the 1989 research on air embolisms used as evidence in the trial. “If my paper was misinterpreted, we have a big problem on our hands,” Lee said in the documentary. After reviewing the evidence, Lee and a panel of fourteen medical experts concluded that “there was no medical evidence to support malfeasance causing death or injury in any of the 17 cases in the trial…We did not find any murders.” Specifically, Lee noted that the skin discoloration observed in Baby Zoe was indicative of hypoxia, not embolism, potentially undermining the conviction. In Zoe’s case, Lee also pointed out that the mother should have received antibiotics to prevent infection, a precaution that was not taken.
Even Dr. Gibbs, the consultant pediatrician interviewed in the documentary, admitted to lingering doubts. “You worry that no one actually saw her do it,” he said, acknowledging a “tiny part of him feels guilty that they may have got the wrong person.”
Despite these challenges, investigators and the mother interviewed in the documentary continue to believe in Letby’s guilt. In July 2025, police submitted additional evidence concerning nine further babies. However, on January 20, 2026, the Crown Prosecution Service announced it would not pursue charges related to these new cases.
McDonald has submitted a request to the Criminal Cases Review Commission for a retrial, leaving the fate of Lucy Letby – convicted serial killer or scapegoat in a tragic series of hospital deaths – hanging in the balance.
