10 septembre 2014

Jack enfin démasqué?

La nouvelle n'a pas manqué d'attirer mon attention! Jetons d'abord un coup d'oeil à l'article original du Mail:

DNA evidence has now  shown beyond reasonable doubt which one of six key suspects commonly cited in connection with the Ripper’s reign of terror was the actual killer – and we reveal his identity.

A shawl found by the body of Catherine Eddowes, one of the Ripper’s victims, has been analysed and found to contain DNA from her blood as well as DNA from the killer.

The landmark discovery was made after businessman Russell Edwards, 48, bought the shawl at auction and enlisted the help of Dr Jari Louhelainen, a world-renowned expert in analysing genetic evidence from historical crime scenes.

Using cutting-edge techniques, Dr Louhelainen was able to extract 126-year-old DNA from the material and compare it to DNA from descendants of Eddowes and the suspect, with both proving a perfect match.

(...) Dr Jari Louhelainen is a leading expert in genetic evidence from historical crime scenes, combining his day job as senior lecturer in molecular biology at Liverpool John Moores University with working on cold cases for Interpol and other projects. He agreed to conduct tests on the shawl in his spare time.
The tests began in 2011, when Jari used special photographic analysis to establish what the stains were.

Using an infrared camera, he was able to tell me the dark stains were not just blood, but consistent with arterial blood spatter caused by slashing – exactly the grim death Catherine Eddowes had met.

But the next revelation was the most heart-stopping. Under UV photography, a set of fluorescent stains showed up which Jari said had the characteristics of semen. I’d never expected to find evidence of the Ripper himself, so this was thrilling, although Jari cautioned me that more testing was required before any conclusions could be drawn.

He also found evidence of split body parts during the frenzied attack. One of Eddowes’ kidneys was removed by her murderer, and later in his research Jari managed to identify the presence of what he believed to be a kidney cell.
It was impossible to extract DNA from the stains on the shawl using the method employed in current cases, in which swabs are taken. The samples were just too old.

Instead, he used a method he called ‘vacuuming’, using a pipette filled with a special ‘buffering’ liquid that removed the genetic material in the cloth without damaging it.

(...) This meant that in order to give us something to test against, I had to trace a direct descendant through the female line of Catherine Eddowes. Luckily, a woman named Karen Miller, the three-times great-granddaughter of Eddowes, had featured in a documentary about the Ripper’s victims, and agreed to provide a sample of her DNA.

Jari managed to get six complete DNA profiles from the shawl, and when he tested them against Karen’s they were a perfect match.

It was an amazing breakthrough. We now knew that the shawl was authentic, and was at the scene of the crime in September 1888, and had the victim’s blood on it. On its own, this made it the single most important artefact in Ripper history: nothing else has ever been linked scientifically to the scene of any of the crimes.
Months of research on the shawl, including analysing the dyes used, had proved that it was made in Eastern Europe in the early 19th Century. Now it was time to attempt to prove that it contained the killer’s DNA.

Jari used the same extraction method on the semen traces on the shawl, warning that the likelihood of sperm lasting all that time was very slim. He enlisted the help of Dr David Miller, a world expert on the subject, and in 2012 they made another incredible breakthrough when they found surviving cells. They were from the epithelium, a type of tissue which coats organs. In this case, it was likely to have come from the urethra during ejaculation.

Kosminski was 23 when the murders took place, and living with his two brothers and a sister in Greenfield Street, just 200 yards from where the third victim, Elizabeth Stride, was killed. As a key suspect, his life story has long been known, but I also researched his family. Eventually, we tracked down a young woman whose identity I am protecting – a British descendant of Kosminski’s sister, Matilda, who would share his mitochondrial DNA. She provided me with swabs from the inside of her mouth.

Amplifying and sequencing the DNA from the cells found on the shawl took months of painstaking, innovative work. By that point, my excitement had reached fever-pitch. And when the email finally arrived telling me Jari had found a perfect match, I was overwhelmed. Seven years after I bought the shawl, we had nailed Aaron Kosminski.

(...) No doubt a slew of books and films will now emerge to speculate on his personality and motivation. I have  no wish to do so. I wanted to provide real answers using scientific evidence, and I’m overwhelmed that 126 years on, I have solved the mystery.

J'ai évidemment lu cette nouvelle avec beaucoup d'intérêt, tout en conservant une bonne dose de scepticisme. Oui, scepticisme. Parce que, tout d'abord, je ne suis pas un scientifique et je ne sais pas à quel point l'analyse est fiable. Aussi parce que le châle lui-même me semble un peu suspect. En effet, cela me semble être une pièce de tissus un peu trop belle pour avoir appartenu à une femme qui était réduite à la pauvreté la plus abjecte.

D'un autre côté, Kosminski est un suspect qui m'a toujours semblé plausible. La dégradation de son état psychologique pourrait expliquer l'escalade de violence et de sauvagerie de ses attaques, et son éventuel internement peut expliquer la fin abrupte des agressions.

Des gens plus calés que moi en science ont depuis soulevés plusieurs points intéressants qui viennent nourrir mon scepticisme:

While there are plenty of criticisms to be made here, the three most important things to keep in mind right now are as follows:

1- Wouldn't you know it, Edwards has a new book to promote. Naming Jack The Ripper comes out Tuesday, and is the latest in a long line of books that speculate on the identity of the infamous killer.

2- Edwards and Louhelainen saw fit to announce their discovery to the world – a discovery based on a "DNA breakthrough" that Edwards describes as "innovative," "amazing," and "incredible" – not in the pages of a reputable, peer-reviewed scientific publication, but the Daily Mail.

3- The discovery hinges on a 126-year-old, unwashed, blood-and-semen-soiled shawl said to have been recovered from the scene of one of Jack the Ripper's murders, though the shawl's actual provenance remains far from certain.

Right. Sure, this is fun and exciting, but take with salt and all that. In the meantime, we look forward to seeing these claims independently verified.

Le fait que les traces découvertes sur le châle soient constituées de génome mitochondrial (ADNmt) pose également problème:

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).

Bref, la nouvelle est certes fort intéressante, mais d'autres tests semblent nécessaires avant de pouvoir affirmer hors de tout doute raisonnable que l'affaire est classée!

Et pour être honnête, ça me plaît bien. Je pense que je serais déçu de soudainement voir disparaître l'aspect mystérieux de toute l'affaire. Parfois, la quête de la réponse est plus envoûtante que la réponse elle-même.

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