Lucy Letby: did she get a fair trial?

In 2003 a Dutch nurse called Lucia de Berk was sentenced to life imprisonment for four murders and three attempted murders of patients in her care. It turned out to be a tragic miscarriage of justice and in 2010 she was freed after the Dutch Supreme Court reopened her case and exonerated her.

The case against Lucia relied heavily on flawed statistics – a case of her being in the wrong place at the wrong time i.e., she was at work when the patients died (sound familiar?). The prosecution claimed in court the chances of so many unexplained deaths was 1 in 342 million and therefore Lucia de Berk was guilty. Two British mathematicians spotted errors in their calculation which turned out to be only 1 in 25. In addition, they said the prosecution had failed to weigh up the probability of another explanation for the deaths. Even if the chance of lots of unexplained deaths is 1 in 342 million, what is the chance that the same patients were murdered? This is also likely to be a very rare event.

When the British nurse Lucy Letby went on trial in the UK I thought about Lucia de Berk. Surely the prosecution in the UK would get a statistician to give evidence? Nope. Not even the defence had a statistician but they likely couldn’t afford it. The defence had only one witness, a hospital plumber, who testified that the aging plumbing systems at the hospital regularly blocked up sending sewage into hand basins on wards. The inference being this could introduce harmful pathogens to the ward.

I did not follow the case closely in the UK and I don’t know whether Lucy is guilty or not but to me the evidence looks flimsy: she was on the ward when babies died, she wrote private notes at home blaming herself for their deaths, and she had what was perceived to be – by the prosecution anyway – an unnatural interest in the bereaved families. There are no fingerprints, no eyewitnesses, no evidence of tampering or fraud, there’s not even convincing evidence of murder. These were sick and often premature babies on an understaffed NHS ward. From where I sit she looks like a hard-working individual with a caring and empathetic nature.

This week the New Yorker published an article about the case. We in the UK are blocked from viewing it but it’s available on the archive: https://archive.ph/dlA3W

The article quotes a law professor at the University of Edinburgh, Burkhard Schafter, who describes the linking of suspicious deaths to Letby as the Texas sharpshooter fallacy which is a statistical mistake where a bullseye is drawn around part of the evidence only. Imagine a gunman firing random bullets at a wall and then finding a cluster of them and drawing a bullseye around that cluster to make it look like he hit the target. Schafter says the police should have looked at all the deaths on the unit and not just the ones in the indictment. It also should have spanned a longer period of time.

The British statistician, Richard Gill, who was paramount in the exoneration of Lucia de Berk wrote a letter to the BMJ in 2023 (the letter has been removed for legal reasons but is still available on his blog) says

I am a coauthor of the report of the Royal Statistical Society https://rss.org.uk/news-publication/news-publications/2022/section-group-reports/rss-publishes-report-on-dealing-with-uncertainty-i/. It is deeply distressing that the police investigation into the case of Lucy Letby and the subsequent trial made all of the mistakes in our book. The jury was never told how the police investigation arrived at that list of “suspicious” events and how it was further narrowed down to the list of charges. This is a case in which a target was painted around a suspect by investigators. We call it confirmation bias, in statistics. It is also often referred to as the Texas sharpshooter paradox.

Many people are convinced of her guilt because of the private notes the police found after searching her home.

The police spent the day searching her house. Inside, they found a note with the heading “NOT GOOD ENOUGH.” There were several phrases scrawled across the page at random angles and without punctuation: “There are no words”; “I can’t breathe”; “Slander Discrimination”; “I’ll never have children or marry I’ll never know what it’s like to have a family”; “WHY ME?”; “I haven’t done anything wrong”; “I killed them on purpose because I’m not good enough to care for them”; “I AM EVIL I DID THIS.”

This doesn’t sound like a narcissistic murderer. It sounds like a woman who is plagued with guilt and self-loathing and is blaming herself for patient deaths. I blamed myself when our Syrian hamsters died. I was very hard on myself and I only see now that time has passed how unfounded this was. And these were just hamsters. I can’t imagine how I might have felt had I been in charge of a ward with very sick newborns who had died. Some people feel guilt more readily than others so perhaps those people who can’t understand these feelings have never felt it themselves and all I can say of that is how lucky you are! People who feel guilt like this are easily manipulated by bad actors who use emotional blackmail and guilt tripping to get what they want.

Here is what Lucy Letby says of the notes during a police interview after being asked whether she had done anything wrong.

“No, not intentionally, but I was worried that they would find that my practice hadn’t been good,” she said, adding, “I thought maybe I had missed something, maybe I hadn’t acted quickly enough.”

The full conversation is in the archive linked above if you want to read it but not once does she confess to murdering anyone and those notes do not make a confession.

If I was a young woman wondering what career path to take it definitely wouldn’t be nursing where it seems someone can randomly blame you for hospital patient deaths based on circumstantial evidence and flawed statistics. I hope Lucy’s case will be reopened and that she’ll get a fair trial.