DNA: Something new and something old
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DNA helix
The biggest story of this past weekend is this L.A. Times piece on the accuracy of the DNA identifications and the statistics used to come up with the probabilities of a random match. Much has been said in the blawgosphere (all of it worth reading) by the Greenfield, the Underdog Mark Katz, the public defender dude and an engrossing lesson in statistics by the Windypundit. They’ve done a wonderful job, so I won’t dwell on it much.
The gist is this: A DNA “match” is when the two pieces of biological evidence share the same markers (loci) at 9 random locations (or 11 or 13 or 15…) The odds of that happening, the State usually contends, is one in 6 billion (and they use that number arbitrarily because it is the population of the world). So in essence, they argue that the only person in the world who could be the source of that piece of DNA is the defendant.
The problem should be evident. Of the millions and billions of loci in the human DNA, 9 or 11 or 15 is an infinitesimal fraction. So, it is possible that if we start looking for matches at 20 or 30 or 100 or 1000 loci, the probabilities will drop. Then we might be talking about 1 in 100,000 or 1 in 20,000. Not bad odds, given the populations of cities and countries.
Still, if these “Arizona searches” (as some are trying to call them in an effort to get the name to stick) haven’t reached your State yet, a number like 1 in 300 billion trillion gazillion quadrasesquecentenellian shouldn’t faze you.
DNA cannot tell a jury when it was deposited or whether the donor actually committed a crime during the deposit. This will not change, even if the odds that it was your guy that deposited the DNA get better.
photo credit: beckita115
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Thanks for the heads up on a couple of blogs that I missed that have a write up on the LA Times article. I thought I had read them all.
I got the links from The Windypundit (my RSS reader broke
) So when are you going to start a blog?
I’ve been debating it for a while now. At some point, I’ll take the plunge. I’m still trying to figure out what sorts of things keep lots of people coming back….an what prompts them to post comments. It’s hard to tell on the legal blogs.
Naturally, I know what I like in a blog, but that doesn’t mean anybody else on the planet likes the same stuff.
Whenever I do take the plunge, I’ll be sure to let you know. It would be nice to have at least ONE reader.LOL!
I think what keeps people coming back is regular posting and not taking yourself too seriously. The rest is eh. Write about stuff that interests you and is generally interesting and you should be all set.
I agree with ya on the regular posting. I’ve never been a fan of blogs with random, drive by, posts. But what about getting people to actually take the time to post a comment? Some blogs have comments up the ying yang & others, you hardly ever see a comment even tho the posts are really good & informative…sometimes even funny. What gives?