Lucy Letby Trial Expert Witness Was Under GMC Probe for Patient Harm Claims
In a startling revelation, it has emerged that a doctor who provided crucial expert evidence in the trial of Lucy Letby was simultaneously under investigation by the medical regulator over allegations of harming patients. The General Medical Council (GMC) initiated a probe into whether Professor Peter Hindmarsh was fit to practise on the very first day he testified in November 2022, a fact that remained undisclosed to the jury throughout the landmark case.
Ongoing Investigation During High-Profile Trial
The GMC investigation was still active when Professor Hindmarsh gave evidence for a second time three months later, amidst what became one of the longest murder trials in British history. As a hormones specialist, he served as an expert witness for the prosecution, supporting claims that Letby attempted to murder two infants, referred to as Baby F and Baby L, by poisoning them with insulin injected into their fluid feed bags.
Great Ormond Street Hospital, where he held an honorary consultant position, reported him to the GMC following an internal investigation by his primary employer, University College London Hospitals Trust (UCLH). Despite this, the jury, which ultimately convicted Letby of seven murders and seven attempted murders, was never informed about the GMC probe or his contract termination by Great Ormond Street in July 2022.
Regulatory Actions and Evidence Concerns
While the GMC conducted its investigation during the trial, a medical tribunal imposed restrictions on Professor Hindmarsh's clinical practice. The tribunal stated, 'There is information to suggest he may pose a real risk to members of the public, if he were permitted to return to unrestricted clinical practice, given the number and nature of the concerns, involving paediatric patients.' Leaked documents revealed allegations included cases of patient harm, issues with diagnosis and treatment, use of treatments in unusual age groups without adequate monitoring, and inappropriate investigations and documentation.
The tribunal acknowledged that these allegations 'may have the potential to impact on his ability to act as an expert witness,' yet allowed him to continue providing evidence. The prosecution was reportedly not informed of the investigation until December 2022, after his initial testimony. Before his second appearance, the prosecution disclosed this to the defence but opposed informing the jury, arguing the GMC probe had not reached a final adjudication.
Controversial Evidence and Ongoing Legal Scrutiny
Professor Hindmarsh testified that blood tests and medical records indicated Babies F and L suffered from hypoglycaemia due to insulin poisoning, likely in their intravenous fluid bags. The prosecution argued this was 'incontrovertible' evidence of deliberate harm, though no direct forensic proof linked Letby to the injections. Judge Mr Justice Goss instructed the jury that if convinced of deliberate harm in one case, they could infer it in others.
However, experts have since criticised the reliability of the insulin tests used, and Letby maintains her innocence, supported by many leading specialists who dispute the prosecution's medical case. The Criminal Cases Review Commission is reviewing her application to appeal, with around 27 experts asserting that natural causes or medical failures could explain each incident. Additionally, a separate police investigation into corporate manslaughter at the Countess of Chester Hospital is underway, with three former senior leaders arrested in June 2025 and currently on bail.
The GMC investigation concluded without regulatory findings after Professor Hindmarsh removed himself from the medical register. He declined to comment, and the GMC noted that interim suspensions or conditions are published on their public register during investigations.
