The Investigation of Lucy Letby is a documentary that investigates one of the most shocking criminal cases in recent British history. The documentary tells the story of Lucy Letby, who worked as a neonatal nurse at Countess of Chester Hospital and received a 2023 conviction for murdering seven infants and attempting to murder seven more between 2015 and 2016.
The film presents a fair assessment of the police investigation since it shows all trial evidence while questioning whether the convictions actually resulted in a significant miscarriage of justice because of possible defects in both medical and circumstantial evidence. The case exhibits its complexity through two sources of evidence that reveal both infant death trends and Lucy Letby’s refusals and the expert testimony about air embolism and hospital staffing shortages.
The 95-minute documentary directed by Dominic Sivyer presents insights which detectives and medical experts and a victim’s parent and Letby’s current attorney provide. The film became available to viewers through Netflix, which started streaming it to audiences around the world on February 4, 2026. The current release occurs during an active investigation, which Lucy letby’s defense team has initiated to examine her case.
The Investigation of Lucy Letby: The rise in infant deaths at countess of Chester Hospital
The neonatal unit at Countess of Chester Hospital experienced an unexpected rise in infant deaths and sudden collapses during the period from June 2015 to June 2016. The unit experienced its normal operational capacity of two to three deaths each year until this time when 13 babies died and multiple others experienced non-fatal medical emergencies. Hospital doctors identified a recurring pattern in which otherwise healthy premature infants developed sudden medical emergencies that included breathing difficulties and skin rashes.
The documentary includes a case study of a baby named Zoe who experienced an air embolism after maintaining good health until that moment. The doctors first thought that the events resulted from natural causes or infections but they began to doubt their initial assessment when the event count started to increase. The nurses discovered through their examination of shift schedules that Lucy Letby worked during all the times when suspicious events occurred.
The deaths ceased after Lucy Letby stopped her medical duties to perform clerical work which began in July 2016 and the unit received a reduction in its high-risk patient admissions. The time period revealed structural weaknesses that included both permanent staff shortages and pipeline failures which likely resulted in infection outbreaks. Medical assessments determined that natural weaknesses in preterm infants resulted in some collapses instead of intentional actions, as per Time.
The investigation and arrest of Lucy Letby
Cheshire Police started Operation Hummingbird in May 2017 because hospitals reported rising death rates as their main concern. Investigators found that Lucy Letby worked during all 17 suspicious cases after they evaluated medical records and interviewed staff members. Police arrested her at her parents’ house on July 3, 2018, after they discovered handover sheets from 250 patients and her personal notes. Letby maintained her innocence during police interrogation while she described her notes as material created from stress and her sheets as material she mistakenly took.
She faced charges for seven murders and 15 attempted murders which were later changed after police arrested her again following her release on bail. The investigation involved forensic analysis of insulin levels in two babies and air injection theories for others. Lucy Letby spent 23 months in custody before trial. The documentary includes unseen arrest footage which shows her calm demeanor and her mother’s distress. Police described the case as unprecedented because they investigated circumstantial evidence which included Letby’s Facebook searches for victims’ families. No new charges were filed in January 2026 after authorities examined nine extra cases, accordign to Time.
Key evidence presented in the trial
The trial against Lucy Letby started at Manchester Crown Court during October 2022 and continued for 10 months. The prosecutors used circumstantial proof which included a staffing chart that documented all times Letby worked at the hospital. Medical specialists proved that some infants experienced intentional damage which included air being injected into their veins to create embolisms and their blood tests revealed insulin poisoning. The comparison of Baby O’s liver injuries established two conditions that produced severe impacts on his body.
Lucy Letby left behind handwritten Post-it notes that contained two statements which she used to admit her wrongdoing. She also took confidential patient records from the medical facility. The defense argued no one witnessed harm, and Letby pleaded not guilty, explaining notes as therapeutic expressions of guilt over unintentional errors. The jury found her guilty on most charges in August 2023 which resulted in a life sentence without parole. Police described the evidence as overwhelming because it depended on indirect evidence which lacked both CCTV footage and known motives. Pathologists observed discrepancies because no needle marks appeared in the cases that allegedly involved injection, as reported by Time.
Doubts and alternative explanations
Post-conviction assessment of evidence reliability raised fundamental questions regarding evidence reliability. Mark McDonald, Lucy Letby’s new barrister, assembled a group of 14 experts who investigated cases and found no intentional harm, which led to deaths from natural causes and infections and hospital errors including staff shortages. Dr. Shoo Lee, who co-authored a 1989 study about air embolisms, claimed that his research results proved that the described rashes showed hypoxia instead of embolisms. The insulin tests were challenged because they might produce incorrect results when applied to preterm infants.
The Post-it notes were reframed as therapy-prompted writings amid workplace stress, not admissions. The hospital experienced a patient capacity reduction because Lucy Letby was removed, which resulted in a decrease of high-risk patients and subsequent lower death rates. A senior judge critiqued prosecution expert Dr. Dewi Evans for possibly biased opinions. The Criminal Cases Review Commission is considering a referral for appeal. Dr. John Gibbs and other original witnesses now show minor doubts about their statements because they cannot prove any physical damage occurred. The points in these arguments demonstrate that the case involves systemic problems instead of individual defendant actions, as per Time.
Insights from the documentary’s interviews and footage
The documentary combines interviews with important people which include detectives who used the evidence to identify Lucy Letby as the only suspect and the mother of the victim who describes her experience of losing her child. Letby’s friend “Maisie” discusses unit dynamics, while barrister Mark McDonald argues for a retrial. The prosecution theories receive support from experts including Dr. Dewi Evans, while Dr. Shoo Lee’s panel results show that no murders occurred. The footage shows Letty’s arrests which include her calm behavior during police questioning and police bodycam footage of their home searches.
The two interviewees appear digitally anonymized through AI which alters their faces and voices according to the technique that the disclaimers explain. The film structures the narrative through its presentation of the prosecution case, which it follows with the defense perspectives that center on evidence disputes including notes and medical tests. The case presents itself as divided, because it reaches no definite conclusions. This approach displays persistent unknowns while refusing to support either argument, according to Time.
Stay tuned for more updates on true crime documentaries.
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Hilfa, Senior Writer at Hilvaro, excels in pop culture journalism. She crafts engaging content on movies, TV, & trends, fueled by her love for storytelling & entertainment.
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