jacobgrey
Joined: Jun 27th, '10, 20:26
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Website: http://www.rhiannondaverc.co.uk
Location: England
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From what I read when that news came out, the Kosminski thing was really just a way to sell someone's book. There's still no definitive proof about whether he was Jack or not. I think there won't ever be, stuff like DNA evidence isn't possible because they didn't follow proper crime scene procedure to preserve the DNA and keep it safe (because of course they didn't know they had to). As I've been reading in my forensics course, so many things can affect DNA testing. Like even if you have two bodies within the same grave you could never, ever be sure you had the right DNA results because of the way that DNA can conmingle and contaminate everything just by proximity.
So take for example a piece of clothing taken a victim, which is what they used. Here's all the ways it could have been contaminated:
1. DNA on there from BEFORE the murder. They were prostitutes, so for example, from any and all clients she had that day/since that piece of clothing was last washed, anyone she lived with, anyone she brushed by in the street, etc
2. DNA from the person that found the body if they touched it or even just stood over it (especially if, and the same for all below, they were sweating/crying/somehow dropping other bodily fluids)
3. DNA from the police investigators on the scene
4. DNA from the coroner who took the clothing from the body, and anyone who touched it there, for example to bag it up or put it away
5. DNA from literally any person who came into contact with it for the whole time it was in storage, during most of which it would not have been in sterilised conditions
6. DNA from items stored in the same place as the clothing, if they were touching or it was placed on the shelf/box/whatever where a previous piece of evidence was placed
And that's even before you get to modern possible contamination. If all steps aren't followed to the absolute book, it's possible, and even common, for contamination from the person doing the testing, from previous tests and samples that have been in the lab that day. There was a high profile tester recently who got struck off and caused a lot of controversy because her lab was found to have tons of contamination dating back years, and this affected some cases where people had been convicted on the strength of DNA analysis alone.
Not to mention that some parts of DNA are passed down through the mother and some from the father and the mother. So a female lineage is best for tracking ancestors, but it's not common to find an unbroken female line for those purposes. As you get further away in generations from the person you're testing for, the results become less accurate. They will only share a percentage of DNA and the percentage you need to get a scientifically acceptable positive will also drop. In other words, matching to relatives is great for parents, siblings and children; less great for grandparents, grandchildren, and cousins; and really not great for the next generation down.
So, TL;DR: DNA analysis from Victorian times has a really, seriously low chance of being accurate, even if it does come up with a seeming result XD
@Mem thanks haha! I forgot that thread of discussion because I got so involved in crime talk  
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