“Jack The Ripper” is arguably the most famous criminal — and certainly the most famous uncaught criminal — in world history. The Ripper was a bloody serial killer who slit the throats and then horribly mutilated the bodies of prostitutes in the foggy Whitechapel district of London in the late 1800s. His brutal murders were prominently reported in lurid detail in the London press of the day and terrified people throughout the world.
Now an amateur sleuth has published a book that contends that DNA evidence reveals that Jack the Ripper was a Polish immigrant barber named Aaron Kosminski, and a number of news organizations are reporting those findings as fact. Should they?
Not so fast. How do you use DNA evidence to conclusively prove who committed terrible murders more than 100 years ago — decades before DNA was even identified by Watson and Crick, much less before DNA tests were developed and DNA samples collected? In this case, the conclusions are based on a single scarf that purportedly is linked to one of the Ripper’s victims named Catherine Eddowes. The DNA test showed that bloodstains on the scarf were linked to distant relatives of Eddowes, while another DNA signature from another substance on the scarf is linked to the distant relatives of Kosminski.
But there are obvious problems. Some people question whether the scarf really has any connection to Eddowes, and in any case it hasn’t been held in scientific isolation all these years; instead, it’s been subject to potential contamination. And an even bigger problem is that the kind of DNA recovered from the scarf is not nuclear DNA, which scientists believe is unique to one human being, but rather mitochondrial DNA, which is passed down from mothers to children and can be shared by large groups of people. The mitochondrial DNA linked to Kosminski is a common subtype — which means that the finger doesn’t point just at Kosminski.
For all of these reasons, Ripperologists are skeptical of this latest claim to have solved some of history’s greatest unsolved crimes. Was Aaron Kosminski in fact the brutal Jack the Ripper? I think we’ll never know.