'The above-mentioned experiment, undertaken by Sherlock Holmes, was based on the work of early forensic expert Robert Christison, who became Chair of Medical Jurisprudence (now called Forensic Medicine) in 1822. He was one of the first toxicology experts and was such a reliable medical witness in court that he became the Crown Witness for the prosecution for nearly 33 years. His discovery of post-mortem bruising occurred during his investigation into one of the most famous serial murder cases in history.'

https://surgeonshallmuseums.wordpress.com/2020/04/17/a-study-in-scarlet-where-fact-meets-fiction/