It is a failure to understand Bayesian probability that is one of the troubling factors here. It's understandable for some members of a jury to be unfamiliar with the concept. It's not acceptable for members of the legal profession to base arguments, submit evidence, give judgments, and issue sentences in profound ignorance of statistical methods. Here's an article by Tom Chivers on the topic. He refers to Letby but omits consideration of her case as proceedings were underway at the time of writing the article. Instead, he illustrates with other instances of similar ignorance of statistical methods.
***It's not acceptable for members of the legal profession to base arguments, submit evidence, give judgments, and issue sentences in profound ignorance of statistical methods***
It's a complex issue. Lawyers should use experts to explain complex stuff to jurors or judges. You can't expect lawyers to be able to assimilate all the salient information in a complex case, and be able to explain it to jurors of unknown intellectual ability.
I know most advocates and barristers are aware of some statistical techniques - especially distribution curves - and some do research to understand things during trials - but it's ALWAYS better to call an expert witness to either explain or refute something.
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