Aaron Kosminski (born Aron Mordke Kozmiński; 11 September 1865 – 24 March 1919) was a Polish barber, hairdresser, and suspect in the Jack the Ripper case.
Kosminski was a Polish Jew who emigrated from Congress Poland to England in the 1880s. He worked as a hairdresser in Whitechapel in the East End of London, where a series of murders ascribed to an unidentified figure nicknamed "Jack the Ripper" were committed in 1888. From 1891, Kosminski was institutionalised after he threatened his sister with a knife. He was first held at Colney Hatch Lunatic Asylum, and then transferred to the Leavesden Asylum.
Police officials from the time of the murders named one of their suspects as "Kosminski" (the forename was not given), and described him as a Polish Jew in an insane asylum. Almost a century after the final murder, the suspect "Kosminski" was identified as Aaron Kosminski; but there was little evidence to connect him with the "Kosminski" who was suspected of the murders, and their dates of death are different. Possibly, Kosminski was confused with another Polish Jew of the same age named Aaron or David Cohen (real name possibly Nathan Kaminsky), who was a violent patient at the Colney Hatch Asylum.
In September 2014, author Russell Edwards claimed in the book Naming Jack the Ripper to have proved Kosminski's guilt. In 2007, he had bought a shawl which he believed to have been left at a murder scene and gave it to biochemist Jari Louhelainen to test for DNA. A peer-reviewed article on the DNA analysis was published in the Journal of Forensic Sciences in 2019. However, scientists from Innsbruck Medical University have criticised the paper and its conclusions, pointing to a number of mistakes and assumptions made by its authors.
