Lucy Letby: Experts cast doubts on serial killer nurse convictions over key evidence and trial fairness

Letby, a former neonatal nurse, was convicted of killing seven babies and attempting to kill seven others, and is now set to spend the rest of her life in prison. However, a growing number of experts are raising concerns about the fairness of her trial, suggesting that vital evidence might have been misunderstood.

Peter Green, a professor of statistics and former President of the Royal Statistical Society, questioned the reliability of a key piece of evidence - a staffing rota showing that Letby was on duty during every suspicious death or collapse between June 2015 and June 2016.

In an interview with the BBC, Prof Green explained: "The chart appears to be very convincing, but there are a number of issues with it. It doesn’t include any of the events that happened when Lucy was not on duty." He cautioned against over-interpreting the data, saying, "It’s a natural human thing. We all see patterns that are not there."

Another critical point of contention is the blood test results that showed two babies had been given an insulin overdose. Forensic toxicologist Professor Alan Wayne Jones, who also spoke to the BBC, questioned the method used to analyse these results.

He said: "The problem is that the method of analysis used was probably perfectly good from a clinical point of view, but not a forensic toxicology point of view." He added, "That test cannot differentiate between synthetic insulin and insulin produced by the pancreas."

Concerns have also been raised about the claim that Letby injected air into the babies' blood vessels, leading to fatal air embolisms. The prosecution relied heavily on a 1989 paper by Dr Shoo Lee to support this charge, but Dr Lee later testified for the defence, challenging the application of his research to this case. Dr Lee was not called to testify during the original trial, a point that has added to the controversy.

Despite these concerns, other legal experts insist that the trial was fair and that the convictions are sound. Barrister Tim Owen KC, who has extensive experience with miscarriages of justice, pointed out in his interview with the BBC that circumstantial evidence can be very powerful when viewed in its entirety. He said: "A circumstantial case can be a powerful case, but in order to understand it, you have to look at the totality."

The debate has led to a private letter signed by 24 experts calling for the upcoming inquiry into the Countess of Chester Hospital and the NHS’s handling of the case to either be delayed or have its terms of reference adjusted. These experts, including Prof Peter Green, stress that they are not declaring Letby's innocence but are concerned about the safety of the conviction. "My concern is simply about the possibility that this was not a safe conviction," Prof. Green said.

Veteran MP Sir David Davis, who has a history of advocating for those wrongfully convicted, has also expressed doubts after being contacted by experts in various fields. In his interview with the BBC, he shared, "I started to think – it’s a terrible crime, but if they’ve got it wrong, it’s a terrible miscarriage of justice."

While acknowledging the gravity of the crimes, he believes it is essential to explore all possible explanations for the deaths, including issues like staff shortages or an infectious outbreak.