Slashdot Mirror
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.
Because the close relative admitted to the crime. duh
(or to use slashdot terminology: read the fucking article)
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.
Most DNA is common, but there are some highly variable sections. Meny of them are just variable length repeats of the same code. If you jhave, at a certain place in the genome, 200 repeats of a particulare sequence, and I have 210, is that shared or not?
The way DNA testing works is to use an enxyme that snips the DNA at cerain codons, then sort the resultant fragments by length. Therefore, in your and my DNA, the fragment containing the sequencee I described above will be a differnt length and will be separated out.Since there are many such sequences in the genome, the chances of individuals other than identical twins haveing the same in all of them is negligible.
Sincec the differnt lengths are largely inherites, with only the odd one or two changing at each generation, there sill also be a considerable commonality between an individual and their bloood relatives.
If you have a large, fresh sample, DNA testing can unequivically say whether the sample did or did not come from a particlar person (or their identical twin). Problems sometimes occur because scene-of-crime samp;es may be old (DNA decays), small (just skin flakes) or ccorrupted (we all, including police officers, scatter our DNA around continually). Such samples are generally beter in steering the police than proving guilt.
Consciousness is an illusion caused by an excess of self consciousness.
Guys and Girls there is a RealVideo clip in the web artical that explains in far more detail how the murderer was caught.
Facts:
Victim stabbed more than 50 times.
DNA samples from flat collected 12 years later, hidden under layers of paint on skirting board.
Rare detail in DNA Component "27" linked to youth, DNA collected after traffic offence.
Convicted murderer was youths uncle.
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)
www.fearthecow.net
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...
- police chief goes on news every day claiming the case is practically over already
- police show themselves completely incompetent
- police chief goes on TV on his knees begging for the murderer to turn himself in, because, obviously, he's pretty much caught already anyway!
- weeks go by
- public becomes angry
- police arrest some random person to appease public
- Slashdot poster is happy that the scumbag is caught, because obviously no one would need such an antiquated thing as a trial to be proven guilty. He was arrested: what more proof do you want?!
Is that basically the timeline of things?In february, an 79 years old lady was raped and murdered in the wood near the place of Emmen in the Netherlands. 90 men were selected by the police for DNA test. It didn't match. Then 1200 people in the neighbourhood of the house of the old lady were intervieuwed and 120 men were selected (made suspicious by their neighbours?) for another round of dna tests. One week ago a match was found and a 29 year old men was arrested who confessed the rape and murder.
I had been running in the wood and my name was noted by the police at the place of the murder. So i was asked to take a dna test and i took it.
Now i have a nice letter from the police thanking me for the cooperation. It also says my dna sample and profile will be destroyed.