Delft Institute of Applied Mathematics

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04 March 2024 15:45 till 16:45

[STAT/AP] Richard Gill: A tale of two Lucys

"Lucia de Berk, a Dutch nurse, was arrested in 2001, and tried and convicted of serial murder of patients in her care. At a lower court the only hard evidence against her was the result of a probability calculation: the chance that she was present at so many suspicious deaths and collapses in the hospitals where she had worked was 1 in 342 million. During appeal proceedings at a higher court, the prosecution shifted gears and gave the impression that there was now hard evidence that she had killed one baby. Having established that she was a killer and a liar (she claimed innocence) it was not difficult to pin another 9 deaths and collapses on her. No statistics were needed any more. In 2005 the conviction was confirmed by the supreme court. But at the same time, some whistleblowers started getting attention from the media. A long fight for the hearts and minds of the pulbic, and a long fight to have the case reopened (without any new evidence - only new scientific interpretation of existing evidence) began and ended in 2010 with Lucia’s complete exoneration. A number of statisticians played a big role in that fight. The idea that the conviction was purely based on objective scientific evidence was actually an illusion. This needed to be explained to journalists and to the public. And the judiciary needed to be convinced that something had to be done about it.

Lucy Letby, an English nurse, was arrested in 2020 for murder of a large number of babies at a hospital in Chester, UK, in Jan 2015-June 2016. Her trial started in 2022 and took 10 months. She was convicted and given a whole life sentence in 2023.

In my opinion, the similarities between the two cases are horrific. Again there is statistical evidence: a cluster of unexplained bad events, and Lucy was there every time; there is apparently irrefutable scientific evidence for two babies; and just like with Lucia de Berk, there are some weird personal and private writings which can be construed as a confession.  For many reasons, the chances of a fair retrial for Lucy Letby are very thin indeed, but I am convinced she is innocent and that her trial was grossly unfair. I will try to convince you, too.

I predict that it will take between 6 and 12 years before she is exonerated."

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