Lucy Letby Case: Expert Witness Under Investigation During Trial

A key prosecution expert witness in the trial of convicted serial killer Lucy Letby was under investigation by the medical regulator at the time he gave evidence, raising questions about the transparency of the proceedings. Professor Peter Hindmarsh, a paediatric endocrinologist, testified about insulin poisoning, a central element of the prosecution’s case against Letby, who was convicted of murdering seven babies and attempting to murder seven others.

GMC Investigation Revealed

The General Medical Council (GMC) launched an investigation into concerns about Professor Hindmarsh, including allegations of harm to patients, on the exceptionally day he began his testimony in November 2022, according to reporting from The Guardian. The investigation continued when he gave a second round of evidence three months later.

Concerns Raised by Hospitals

Great Ormond Street hospital reported Hindmarsh to the GMC following an internal investigation led by University College London hospitals trust (UCLH). The concerns included allegations of “identified cases where harm to patients has been alleged,” as well as issues with his “diagnosis and treatment of patients,” “use of treatments in unusual age groups, without adequate monitoring,” “inappropriate investigations,” and inadequate documentation.

Jury Unaware of Investigation

Crucially, the jury was never informed about the GMC investigation or the concerns raised about Professor Hindmarsh’s fitness to practice. The Crown Prosecution Service (CPS) opposed informing the jury, arguing that the allegations hadn’t reached a final adjudication.

Tribunal Restrictions and Continued Testimony

Despite the serious concerns, a medical tribunal permitted Hindmarsh to continue providing expert evidence in the Letby trial. Although, the tribunal imposed restrictions on his function, stating he “may pose a real risk” to the public and that the allegations “may have the potential to impact on his ability to act as an expert witness.” The tribunal required him to inform any party instructing him that he was under GMC investigation, a requirement under criminal procedure rules.

Hindmarsh’s Evidence and the Insulin Cases

Hindmarsh’s evidence centered on the prosecution’s claim that Letby poisoned two babies, referred to as F and L, with insulin. He testified that blood tests and medical records indicated the babies suffered from hypoglycemia due to insulin poisoning. These insulin cases were considered pivotal in securing the guilty verdicts, with the judge instructing the jury that evidence of deliberate harm in one case could be inferred in others.

Challenges to the Prosecution’s Medical Case

Since the convictions, numerous medical and scientific experts have questioned the prosecution’s medical case, including Hindmarsh’s evidence. A 14-member expert panel, led by Dr. Shoo Lee, unanimously concluded that the babies died or collapsed due to natural causes and poor care, finding no evidence of murder or deliberate harm. These experts have contested the reliability of the insulin tests used and Hindmarsh’s calculations, arguing that alternative explanations for the babies’ hypoglycemia were not adequately considered.

Criminal Cases Review Commission Review

Letby’s lawyer, Mark McDonald, has applied to the Criminal Cases Review Commission (CCRC) to have her case reviewed, supported by reports from 27 leading experts. The CCRC is currently reviewing the application.

Hindmarsh’s Registration Status

Professor Peter Hindmarsh is no longer registered with the GMC, having relinquished his registration on November 14, 2024, effectively ending the GMC investigation. According to the final judgment in R -v- Letby, Professor Hindmarsh held concurrent registration with the General Medical Council and had the requisite experience.