Sometimes I comb my hair, or bite my fingernails. What if part of it fell on the floor and some random person steps on it. Stuck on the bottom of their shoe. A bunch of coincidental stuff comes up and my DNA is tested against a fingernail/hair under victim's shoe... match. I'm doomed.
Indeed, I fear the mentality that DNA-match = Guilty.
How many people have been sent to jail/put to death based on false DNA results or even accurate but not via the crime they're accused of.
This is a plot point in the film Gattaca. I'd recommend watching it if you haven't already:
You don't even need to comb your hair to leave DNA all over the place. A normal person will lose 50-100 hairs every day.[0]
Also, everyone sheds dead skill cells, and certain dermatological conditions can exacerbate matters.
[0] http://www.aad.org/dermatology-a-to-z/diseases-and-treatment...
True. If you're in an office you haven't visited before and would like to be disgusted, examine the bottoms of a few mice.
The problem with DNA evidence is that prosecutors like to jump to the end, the idea that a DNA match means that someone with DNA identical to that found at a crime scene has been found. In reality there is a long string of assumptions that must hold true in order for that supposition to also be true. The chain is only as strong as its weakest link.
Unlikely? It's very likely. We interact with tons of people each day. Also consider cases were the DNA is from a person close to the victim, but who isn't the murderer. Perhaps a friend came by the house and then left, and another came in and did the murder. Or a person sleeps with someone (perhaps an one-night-stand) and then is murdered, say by a jealous partner. The DNA could be from an interaction previous to the murder.
And of course, if the police is "sure" they have the suspect (like they often are, especially is he's say black or poor or something like that), they would also consider it "OK" to plant some DNA obtained for him to be "discovered" in the murder scene. Police has been found (in court) pulling such shit with falsified evidence) for decades.
People don't seem to realize how valuable and many times private DNA information really is otherwise a large number of them would have resisted this dragnet.
Am I the only one thinking this kind of large scale collection of DNA information should no be allowed without some very powerful circumstantial evidence.
Not just you happen to live in the same city a person was murdered in.
http://en.wikipedia.org/wiki/Colin_Pitchfork
Particulary interesting to me is the fact that the initial mass screening did not find the perpetrator, because he had paid somebody to give a sample for him. But he was eventually caught because the stand-in couldn't (or didn't want to) keep a secret.
Wikipedia mentions no controversy, although of course that doesn't mean there wasn't one.
I wouldn't mind submitting a DNA sample if it helps the police find a murderer. Maybe it was some distant cousin of mine, and my DNA will help them narrow their search.
There's two different logical errors involved. First, jurors conflate proving the assertion "this is the defendant's blood" with "the defendant killed the victim." Second, the "one in a billion" theoretical random match odds turn into more like "one in several thousand" when accounting for laboratory error. In fact, laboratory error totally dominates the error rate of the overall process.
http://www.extremetech.com/extreme/126843-think-gps-is-cool-...
From the article it sounds like from where the DNA was located and other corraborating evidence that this guy is guilty. But I'm glad the article ended by saying some of the geneticists weren't condemning the accused based on the DNA evidence alone. I hope that type of thinking expands into the wider public.