New DNA Test to Solve More Cases 65
Krishna Dagli writes From the BBC,"Tens of thousands of unsolved crimes could be cracked with a new forensic technique, it has been claimed.The Forensic Science Service (FSS) is piloting a computer-based analysis system which can interpret previously unintelligible DNA samples.It claims the technique is a world first which will boost its crime detection rates by more than 15%.The method is being tested by the West Yorkshire, South Yorkshire, Northumbria and Humberside police forces."
Re:Suspect Database (Score:3, Informative)
Re:You mean... (Score:3, Informative)
The DNA can be a match and still not come from the suspect. All DNA is based on statistics.
Marker A is in 0.25% of the population, Marker B is in 0.01%, C is in 0.3% and D is in 0.01% and E is in 1/3. That means that if someone has ABCDE they are 1 in 400,000. Granted, those aren't exactly real numbers and the tests can use over 10 different markers, but it gives you an idea of how the system works. Currently, it is impossible to say DNA X deffinitely came from suspect Y. It is possible to say that there is a Z% chance, though. That is how the system actually works.
I'm reminded of a case in which a paternity test said that a guy was the father when he had never had sex with the mother. Then there is the mother who was not the biological mother of the child she gave birth to (and no invitro or egg donation was involved).
Re:Suspect Database (Score:2, Informative)
The original tests looked for a certain number of snippets of DNA that were considered "genes". Fewer than a dozen at first, but towards the end of this test's usage, they were up to about 16. With only 2^16 possibilities ("there or not there", 16 times), it matched you, probably your family members, and about 50 thousand other people, assuming that none of those snippets of DNA were actually the gene for having two arms or something like that, since they didn't really know how all that worked back then.
Now that they have a better idea of how genetics works, they match based on the distance between particular genes on a chromosome. Every time people mate, the chromosome swap doesn't always line up the exact same way leading to genes that move up or down, or so the theory goes. Nobody is actually sure how accurate this is, the only studies done have been by the companies selling the kit or by criminal justice researchers, but simple logic dictates that the gene can only move so far before it runs into another important part of the sequence (unless it moves too, and if all the genes move at once, then the distance between them hasn't changed at all!), meaning that there is some finite limit to the variations this can map.
The only true way to genetically identify someone would be a complete map of at least one chromosome, and preferrably more. The Y chromosome matches every generation in a lineage of men, likewise, the X in a male identifies his mother and brothers, so those are disqualified. Of course, a complete map is ridiculously expensive and time consuming, and in these days of money going to bridges to nowhere and websites to track the money that went to bridges to nowhere, justice has to be done on a discount.
So what does this mean? It means that when the government starts collecting DNA samples from anyone and everyone, they'll have a pool of positive matches from which to pick the easiest sucker to blame the crime on. Of course, the prosecuting attourney won't mention that there are other people who match that sample, when he presents the "evidence" to the jurors, and the expert witness they paid to lie (have you ever seen a prosecutor prosecute their own star witness for perjury? I haven't [offthekuff.com]. They always seem to be just "wrong") will neglect to mention that there were other matches, but they were either politically inconvenient (lol republican [bradblog.com] lol) or just plain rich. They won't need to worry about motive, alibis, or anything else, because the prosecutor will convince the jury who has watched far too much Law and Order that the DNA test is perfect.
Or hell, they could just do what Houston does, and just lie through the teeth about the whole thing [chron.com].
For you non-wetware workers (Score:5, Informative)
The "new" stuff here is that they have come up with software which will allow the system to extract 2 sets of "seial numbers" from one reaction. Like having 2 fingerprints on top of one another and seperating them to determine the swirls. They also are claiming a more sensitive technique which will allow for smaller or partially degraded samples to be tested, but this is probably just tweaking the experimental protocol.
This is no new test, just tweaks and algorithms.