A media frenzy erupted in early September 2014 when it was announced that a British author named Russell Edwards was about to publish a book (titled Naming Jack the Ripper) in which he claims to have found DNA evidence that proves Aaron Kosminksi was Jack the Ripper. The Casebook website has been inundated with inquiries surrounding these claims, so to help answer some of the most frequently asked questions, we're offering a brief primer, below.
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Has DNA evidence really proven that Aaron Kosminski was Jack the Ripper?
The claims being made in the media are certain attention-grabbing, but many of them seem to be - at least at this point - wildly overblown. What we know so far is that a British author, Russell Edwards, has claimed to have found a "DNA match" between blood and/or semen found on an old shawl purported to have been taken from the Catherine Eddowes crime scene (generally believed to have been Jack the Ripper's fourth victim) and DNA samples taken from modern-day descendants of the family of Aaron Kosminski. It sounds quite impressive, but there is more to the story.
Problem #1: The shawl has no provenance linking it to Catherine Eddowes
The shawl in question is not new evidence - it has been widely known to exist for at least two decades. The shawl was kept by a family in Essex for many years. They claimed to have had an oral tradition stating that it was taken from the Catherine Eddowes crime scene by an ancestor of theirs, police constable Amos Simpson. The shawl was never mentioned in the official police inventory of the crime scene. There is also no record of PC Amos Simpson ever being at the crime scene. Finally, the shawl is of a relatively expensive type - one unlikely to have been worn by Catherine Eddowes, who was essentially penniless and living on the streets at the time of her death. The only evidence to date linking the shawl to Catherine Eddowes is "family tradition."
That said, Mr. Edwards claims to have found DNA evidence on the shawl linking it to Catherine Eddowes. If true, this would make any concerns about the "family tradition" moot. However…
Problem #2: The vagaries of mitochondrial DNA evidence
Very little precise information has been released yet concerning the nature of the DNA evidence Mr. Edwards claims to have found. A few articles have suggested that the DNA being examined was mitochondrial DNA. It is important to understand the difference between a "DNA match," like those seen on a CSI television show, and a "mitochondrial DNA match". mtDNA, unlike nuclear DNA, is not unique. Finding an mtDNA match between two samples does not mean that one person left both, but that only a certain percentage of the population could have left both. These percentages can vary from anywhere between 1% and as much as 40% of the population. Finding an "mtDNA match" doesn't generally mean you've matched one person definitively - it means you've matched the population group to which that person belongs to the population group of the person who left the sample.
The best that can be said for such an mtDNA match is that it doesn't exclude Kosminski from being the source of the DNA. He could have left it, yes, but so could any one of hundreds of thousands, perhaps millions, of other people who share that same mtDNA profile. Or, as Alan Boyle, science editor at NBC News, wrote:
MtDNA is passed down from a mother to her children, and many people can share the same mtDNA signature. The signature linked to Kosminski, T1a1, is a relatively common subtype. Thus, the determination doesn't mean much unless the signature can be narrowed down to a rarer subtype, or unless additional evidence can be brought to bear (as was the case for identifying the remains of Russia's Czar Nicholas II and his family).
Problem #3: Issues of contamination
Leaving behind all the problems of provenance and mtDNA, there is the very real issue of contamination. After all, the shawl has not been kept vacuum-sealed for the past 106 years. It has presumably been handled, worn and shuffled around for at least 80-90 by the family or families that originally owned it, and then handled and shuffled around even more after it was widely revealed to the Jack the Ripper community in the 1990s, and by the auction house that eventually sold it to Mr. Edwards. On top of that, we know that bleach has been applied to at least portions of the shawl (it was said that an early owner of the shawl wanted to try to "remove the bloodstains").
All of this activity has potentially not only degraded any DNA that may or may not have been left there by its original owner, but it has more than likely added substantial amounts of foreign, third-party DNA accumulated over years of handling by family members, researchers, auctioneers and the general public.
We've been down this path before. Patricia Cornwell published a best-selling book in 2002 in which she claimed to have found mtDNA evidence linking the famous Victorian artist Walter Sickert to several letters purported to have been written by Jack the Ripper. There was a big media fuss at the time, but after a while it became clear there were no good answers to the questions of provenance and the vagaries of mtDNA evidence. The media circus petered out, and there are few, if any, historians today who believe hers to be the "final solution."
In this case, Mr. Edwards has a bit of an advantage over Ms. Cornwell, in that his suspect (Aaron Kosminski) was a person under legitimate police suspicion at the time of the murders. In fact, Kosminski is widely regarded as one of the "least unlikely" suspects yet put forth, and there are several books already published that have tried to prove his guilt in these murders.
One can only applaud those willing to take a scientific approach to the Jack the Ripper mystery. But remember - the beauty of science is that it can be independently tested and verified. As it stands right now, Mr. Edwards' claims must be taken with a heavy dose of salt until they have been independently verified and published in a reputable peer-reviewed journal.
— Naming Jack the Ripper is due to be published on September 9th, 2014 by Globe Pequot Press.
You can also read more about Aaron Kosminski, Catherine Eddowes and the Eddowes' shawl via the following links: