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Twist on DNA Privacy
ConfusedVorlon writes "The BBC is reporting the conviction of a man for the murder of a prostitute 15 years ago. The interesting twist is that his DNA was not on record - 'But it partly match[ed] that of a youth's who was known to the police - but who had not been born at the time of the murder. The teenager, it turned out, was a close relative of [the murderor].' There has been concern in the past at the idea of keeping DNA of those interviewed but not charged with crimes. I haven't previously heard of the privacy implications of being related to a criminal/suspect. If you've done nothing wrong, you've nothing to fear?"
If you feel the need to object to DNA privacy issues, bear in mind that three men were wrongly convicted of the murder initially and cleared much later before a new investigation finally caught the real perpetrator.
Its obvious from a couple or three replies already up that some of you are not reading the article first.
The dude was not convicted on the DNA evidence alone. In fact, there apparently was no trial. The DNA only lead to a suspect...who then CONFESSED AND PLEADED GUILTY.
I fail to see where there is a privacy implication here. All I see is good police work (which makes up for the initial very bad police work).
I want a new quote. One that won't spill. One that don't cost too much. Or come in a pill.
Except that the guy pleaded guilty once arrested, so the DNA was not called in evidence.
But once they had arrested the guy, they had a sample of *his* DNA, which should be an exact match for the scene-of-crime DNA. The critical bit is the police working back through somebody else's DNA that they just happened to have on file.
Consciousness is an illusion caused by an excess of self consciousness.
There are two ways of comparing DNA that are used. The first, more common method, is to look at something called Restriction Fragment Length Polymorphism (RFLP). The spaces between known regions that can be cut vary. Look at enough of these and you can statistically say with some confidence that its your person.
The second method, which isn't used as often last I saw, involves looking at the DNA sequences in regions which do vary. Perhaps well studied regions like those associated with organ rejection in transplantation.
Both methods are more reliable than the people carrying out the work. With RFLP, there is a certain amount of subjectivity involved in calling two sizes the same. With sequencing, contamination is easy.
I'm sure the procedures have improved since I last observed them. The weakest link in both procedures is the human factor.
The biggest problem with DNA fingerprinting, is the contamination problems. Before a restriction endonuclease (DNA cutter) is added to cut up the highly repeated elements of DNA, PCR (polymerase chain reaction) is used to make many, many copies of the DNA. (2^20 to 2^30 iirc)
The big problem with this is, that a tiny contamination will cause deviances from what would be expected.
As most uni (college) biology students will tell you, it's really easy to contaminate what you're working with if you're not careful, when you're using PCR. As a crime scene is certainly not a lab, the potential for getting the wrong DNA is possible in some cases.
Although, I imagine that this is mitigated somewhat by obtaining DNA samples of the victim, and others who may have legitimately contaminated the scene.
There's a difference between showing that DNA at a scene matches a suspect, and showing that the DNA at the scene was there because of the criminal activity.
I'm not saying that DNA fingerprinting is not a legitimate technology, it's just like all technologies - not foolproof, and we should remember that, rather than treat it like a panacea.
(And for those people worried about insurance companies, etc, the police DNA database does not contain information about whether you are more likely to get any particular disease)
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A common question.
A good primer: How DNA Evidence Works
Whenever the offence inspires less horror than the punishment, the rigour of penal law is obliged to give way...