The True Story Behind The Investigation of Lucy Letby
The neonatal nurse Lucy Letby became notorious in the United Kingdom when she was found guilty of doing the unthinkable. In 2023, Letby was convicted of the murder of seven babies and the attempted murder of an additional six infants (a seventh charge for attempted murder came later). That made her one of the most prolific female serial killers in the U.K. But a new Netflix documentary, The Investigation of Lucy Letby, seeks to shed new light on the trial and challenge our understanding of Letby, suggesting she may not be guilty after all.
[time-brightcove not-tgx=”true”]This is the story of Lucy Letby, according to the bombshell Netflix documentary.
Letby was born on Jan. 4th, 1990. She attended the University of Chester, where she got a BSC in Child Nursing. She had her university placement at the Countess of Chester Hospital in Northern England, and started working there full-time after getting her degree in the neonatal department. “There was nothing about her that made her stand out to me,” recalls Dr. John Gibbs, a retired consultant pediatrician, in the documentary.
Yet in June 2015, something strange was going on. Babies were mysteriously dying at the Countess of Chester Hospital. One of the babies was named Zoe (her name has been changed in the documentary), and her mother (who is anonymized by AI in the film) recounts her story. The mother had an extremely challenging birth, and Zoe was taken to intensive care and put in an incubator. She was responding well, as expected, but suddenly she collapsed, and the doctors were unable to save her, and she died on June 22. Three other babies died at Countess of Chester on June 8, 14, and 22, 2015. By February 2016, the death toll had risen to nine. By the following June, it was thirteen. “In the 21 years I’d been a consultant, I’d never seen anything like this before,” recalls Gibbs.
An investigation was opened, and a pattern emerged: Letby was the only nurse on duty for every suspicious death in the neonatal unit. The manager of the unit was sure of Letby’s competence, but eventually Letby was removed from the night shift and brought onto the day shift. The collapses and deaths decreased significantly during the night, but then started to occur during the day, the documentary alleges.
On July 3, 2018, Letby was arrested. The police searched her home and found concerning materials, including a box of confidential handover sheets and documents about the babies, many of which related to the babies that collapsed and subsequently died. Letby had over 250 of them and arranged them in chronological order. When questioned by the police, she claimed that she brought them home by accident.
After being let out on bail on two previous occasions, on Nov. 10, 2020, Letby was arrested for a third time. Twenty-four hours later, she was charged with eight counts of murder and 10 counts of attempted murder. She was denied bail and spent 23 months in custody before facing trial. On Oct 10, 2022, the trial began. Prosecution detailed some of the ways Lucy would harm the children. They claimed she removed airway tubes or would overfeed to inflate the stomach, thereby restricting breathing. Prosecution said she was creative in her methodology and changed things so as not to get caught.
With Baby Zoe, there was a strange skin discoloration that doctors had not seen before. There was also air found in a blood vessel in the body, an air embolism. According to medical examiner Dr. Evans, Zoe’s deterioration was caused by a deliberate injection of air into the intravenous system. Letby would also message her colleagues about the deaths and would look up the parents of the deceased babies on Facebook, though the evidence was all circumstantial.
Two of the babies Letby was accused of harming were given insulin when they did not need it, which is extremely dangerous. This was, according to the medical examiner, the “smoking gun” to the rest of the case. Found at Letby’s home was a series of post-it notes, scribbled with phrases like “I killed them,” “I am evil,” and “I did this.” The evidence, though largely circumstantial, was overwhelming. “Objectively, it couldn’t have been anyone else,” observes Simon Blackwell, Detective Superintendent, Cheshire Police. Letby maintained her innocence throughout and pleaded not guilty.
On Aug. 18, 2023, the verdict was delivered: Letby was found guilty of murdering seven babies and attempting to murder seven more. She was sentenced to life in prison.
The world became convinced that Letby was a prolific serial killer, but others were unsure, and The Investigation of Lucy Letby casts doubt on the trial. Mark McDonald, a criminal defense barrister, now representing Letby, is fighting for Letby’s freedom. He highlights in the documentary that there was no motive, no CCTV evidence, and nobody actually saw her do anything wrong. The post-it notes claimed she was responsible this, but there were other words in the notes, like “slander” and “discrimination,” that suggest she didn’t really believe she did it, rather than that she was just trying to process her feelings, he says. She was told, according to McDonald, as a form of therapy, that she should write down her feelings as a form of therapy.
A 2024 article in The New Yorker written by Rachel Aviv also cast doubt on the court’s guilty verdict. Aviv’s reporting found that the issue may not lie with Letby, but rather the hospital itself. Because Letby was more qualified than most nurses, she was given the sickest babies. “It would be odd if she wasn’t there when something went wrong,” McDonald says. He notes how the prosecution kept pushing the idea that the babies stopped dying when Letby was taken off the unit. But when Letby was taken off the unit, McDonald explains, it was downgraded, meaning it didn’t receive as many seriously ill babies. “The mortality rates were always going to drop,” he says.
McDonald has made several media appearances, casting doubt on the result of the case. His campaign has gained considerable traction, and amongst those pushing for Letby’s freedom is Sir David Davis, a sitting UK member of parliament. Davis has campaigned for a retrial of Letby, observing that the trial was a “clear miscarriage of justice.”
The evidence in the trial, according to McDonald, all centers around the expert witness Dr. Evans. McDonald reveals that a senior judge, not involved in the trial, let the trial judge know that Evans “makes no effort to provide a balanced opinion,” and that “no attempt has been made to engage with the full range of medical information.” This is shown in the documentary in close-ups of the letter sent from a senior judge, though we do not learn the identity of the judge.
To verify whether Evans would be a reliable expert, McDonald contacted the original author of the findings about air embolisms that Evans used as evidence to convict Letby. Professor Shoo Lee, in Alberta, Canada, published the paper in 1989. “If my paper was misinterpreted, we have a big problem on our hands,” Lee says in The Investigation of Lucy Letby. After going through the evidence, Lee says, “they did not describe the kind of skin discoloration that was diagnostic of embolism. What they had described was skin discoloration due to hypoxia, or lack of oxygen. This means that the conviction was potentially wrong.”
Lee assembled a panel of fourteen medical experts who 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.” In the case of Zoe, Lee notes that the mother should have been given antibiotics to prevent infection for the baby, but this wasn’t done.
Dr. Gibbs, the consultant pediatrician interviewed in the documentary, says that Letby was correctly put in jail, but he admits that a tiny part of him feels guilty that they may have got the wrong person. “You worry that no one actually saw her do it,” he says.
Investigators and the mother interviewed in the documentary maintain that Letby is guilty. In July 2025, the police submitted additional evidence regarding nine further babies. On Jan. 20, 2026, the Crown Prosecution Service said it would not charge Letby with any further offences.
McDonald has submitted a request to the Criminal Cases Review Commission for a retrial.