In the aftermath of one of the most harrowing criminal cases in recent British history, the conviction of former neonatal nurse Lucy Letby for the murders of seven babies and the attempted murders of several more at the Countess of Chester Hospital is once again under fierce scrutiny. As new theories emerge and doubts around the evidence multiply, a fresh wave of documentaries, expert reports, and ongoing investigations are fueling a maelstrom of uncertainty—leaving the public, the medical community, and the justice system grappling with the question: did she really do it?
Lucy Letby, once described as a model nurse, was found guilty in 2023 after a lengthy trial that gripped the nation. The prosecution painted her as a cold-blooded killer who used her trusted position in the neonatal intensive care unit to inflict catastrophic harm on the most vulnerable patients. Between 2015 and 2016, the hospital saw nearly three times as many newborn deaths as would be considered normal, a statistic that became a central plank of the prosecution’s case. Letby was sentenced to 15 whole life sentences, a rare and severe punishment ensuring she would never be released.
But as reported by The Sun and The New Yorker, a growing chorus of expert voices is now casting doubt on the evidence that led to Letby’s conviction. The most recent BBC Panorama documentary, aired in August 2025, is the third in a series examining the case. Titled Who to Believe?, the episode delves into the shifting sands of expert testimony, the reliability of forensic tests, and the sheer complexity of the case—ultimately concluding that the truth remains maddeningly elusive.
The documentary, as reviewed by The New Yorker, highlights the confusion that has come to define the Letby saga. It scrutinizes the testimony of Dr. Dewi Evans, the prosecution’s key expert witness, who notably changed his opinion about the cause of death of one of the babies—from air pumped into the stomach to intravenous air embolism. The program features a pointed exchange between investigative journalists Judith Moritz and Jonathan Coffey, with Coffey remarking, “Some people would say that’s exactly what we’re dealing with here,” when Moritz likens the shifting expert testimony to changing a cause of death from a gunshot wound to drowning. The program concludes, “It’s certainly a difficult case to get your head around,” capturing the prevailing sense of confusion.
Adding another layer to the debate, a new 173-page report by Professor Geoff Chase and chemical engineer Helen Shannon, submitted to the Criminal Cases Review Commission (CCRC), challenges one of the prosecution’s key arguments: that Letby poisoned two babies, known as Child F and Child L, with insulin. The prosecution’s case hinged on blood tests showing elevated insulin levels, which, according to biochemist Dr. Anna Milan, could only be explained by insulin being administered to the babies. But Chase and Shannon dispute this, suggesting that the court underestimated how much insulin would be needed to cause harm and failed to account for the natural presence of insulin-binding antibodies in premature infants.
Professor Chase told The Telegraph, “The trial stated no insulin was missing and it would require only a very small drop. If injected intravenously yes, this is true, but with adsorption, or sticking, it would require between 1.2 teaspoons to six to seven vials.” He added, “If no insulin is missing, there is no way to commit that crime. Insulin sticking to lines, bags, tubes is a known thing and it can significantly impact, for example, insulin pump use among small children. The lack of missing insulin is the true smoking gun in this case. Simply, there was no possibility to commit insulin poisoning as hypothesised in court.”
The report further argues that premature babies, especially those treated for infections or with antibiotics—as was the case with Child F and Child L—often have insulin-binding antibodies that can cause insulin to linger in the bloodstream for weeks, potentially explaining the abnormal test results. “When a newborn or mum is exposed to bugs or certain antibiotics, insulin levels can shoot through the roof,” Chase explained. “Once those antibodies bind to the insulin, it can hang around in the blood for days, weeks, or even months.”
Despite these plausible explanations, the Liverpool lab that conducted the original blood tests never performed the additional tests required to check for these antibodies. A warning note from the lab made it clear that their equipment couldn’t distinguish between injected insulin and naturally occurring insulin, and advised sending samples to a forensic lab for further analysis. However, those tests were never carried out, and by the time Letby’s defense team requested a second opinion, the blood samples had already been discarded.
Letby has always denied the charges against her. She lost two attempts to overturn her convictions at the Court of Appeal in 2024, but her case is now under review by the CCRC, which investigates potential miscarriages of justice. Meanwhile, three former senior staff at the Countess of Chester Hospital have been arrested on suspicion of gross negligence manslaughter, and Cheshire police are conducting a separate investigation into other deaths and non-fatal incidents at both the Countess of Chester and Liverpool Women’s Hospital, where Letby trained from 2012.
The media’s role in shaping public perception of the case has become another point of contention. The Panorama documentary, as well as ITV’s Lucy Letby: Beyond Reasonable Doubt?, have both been criticized for their muddled presentation of competing theories and for failing to provide any definitive answers. As The New Yorker noted, “In determinedly not taking any claims at face value, Who to Believe? will surely confuse viewers even more, and brings us no closer to understanding whether there is indeed a compelling alternative to the events set out by the prosecution.”
At the heart of the controversy is the question of whether Letby was “spectacularly bad” at her job, or whether the British justice system has committed a major miscarriage of justice. The lack of consensus among experts, the limitations of forensic testing, and the persistent gaps in the evidence have left the case wide open to interpretation—and to further investigation.
As new revelations continue to surface and the CCRC review presses on, the Letby case stands as a sobering reminder of how fragile certainty can be in the face of tragedy and complexity. For now, the only thing that seems clear is that the search for truth is far from over.
