Colin Norris, a former nurse, was convicted in 2008 for the murders of four elderly patients and the attempted murder of a fifth at hospitals in Leeds. The prosecution's case relied heavily on the theory that Norris administered lethal doses of insulin to patients who were not diabetic, leading to fatal hypoglycemia. He was sentenced to life imprisonment with a minimum term of 30 years.

However, a new investigation by the BBC has raised significant questions about the medical evidence presented during his trial. The report highlights that the scientific understanding of insulin-related deaths has evolved since 2008. Experts interviewed for the podcast suggest that the patients' deaths could potentially be explained by natural causes or underlying health conditions rather than intentional poisoning. This has prompted renewed scrutiny into whether the original clinical evidence was sufficient to support a murder conviction.

While the BBC report focuses on the possibility that the crimes may not have occurred as described, it does not definitively clear Norris. The legal system has yet to formally review these specific claims in a new appeal. The case remains a subject of debate regarding the reliability of medical testimony in criminal trials and the potential for miscarriages of justice when complex clinical data is interpreted by juries.