Scientists and Lawyers Argue For Open US DNA Database 120
chrb writes "New Scientist has an article questioning the uniqueness of DNA profiles. 41 scientists and lawyers recently published a high-profile Nature article (sub. required) arguing that the FBI should release its complete CODIS database. The request follows research on the already released Arizona state DNA database (a subset of CODIS) which showed a surprisingly large number of matches between the profiles of different individuals, including one between a white man and a black man. The group states that the assumption that a DNA profile represents a unique individual, with only a minuscule probability of a secondary match, has never been independently verified on a large sample of DNA profiles. The new requests follow the FBI's rejection of similar previous requests."
Independent Databases (Score:4, Informative)
"Time for DNA Disclosure" letter can be read... (Score:5, Informative)
Re:Misuse Of Statistics (Score:5, Informative)
Another misuse of statistics: Many people expect that FBI uses the DNA database in the following way:
1. get DNA sample from the crime scene
2. match DNA sample against all samples in the database
3. if you got a match, you got the killer.
This is not how it works. Say the real odds of a false positive are ten million to one. In a country of say 300 million people this still gives an expected 30 people who match the sample from the scene. Is each of them the criminal? Clearly not.
How it really works? Imagine that you already identified several suspects. If you take DNA samples of these few people and one of them matches the DNA from the hair from the scene, you can still conclude that given your knowledge, with a very high probability the person in question was present at the crime scene.
In other words, using DNA tests is perfectly reasonable as long as you know what you are doing, even if the probability of a false positive is several orders of magnitude larger than one to a billion.
FBI using outdated technology (Score:5, Informative)
The FBI's database only uses 15 markers, checking 15 sites in DNA. That's not good enough, and there are false matches. [nacdl.org] The problem is that they're using DNA technology from about 1990.
23andme, the commercial DNA analysis service, checks 580,000 sites in DNA. 23andme probably has enough data to validate the quality of the FBI's marker selection. That's a good way to check. Identical twins do match, even at the 23andme level of analysis.
Similar to the Birthday Problem (Score:4, Informative)
Its similar to the birthday problem. Given a class of 35 students the odds that one of them has the same birthday as yours are 35/365 = 9.5%. However, the probably that there are two students in the class who have the same birthday (not necc yours) is about 81% (check Birthday Problem on Wikipedia).
Its the same here. The probability of there being matches between different people in a large database of DNA is going to be a lot higher than the probability that there is a match to a given person or crime scene DNA.
Re:p = (1/4)^(#base pairs)? (Score:5, Informative)
Forgive me that I'm a layperson who didn't RTFA
I'd forgive you, but the article was written for lay people and it clearly answered your question.
I was always assuming that, given that scientists who know what they're doing should have invented this test, there was some sophisticated process that would ensure that they would somehow only choose base pairs from the subset that was actually different in different individuals
If you had read the article, you might have noticed that it says the test selected for non-coding DNA (that is it doesn't produce proteins) that commonly varies in humans.
Re:chimps have 97% of human DNA (Score:5, Informative)
This innocent man:
http://en.wikipedia.org/wiki/Cameron_Todd_Willingham [wikipedia.org]
Was found guilty and executed by testimony from BOTH a mistaken expert witness and multiple eye witnesses.