TheAgitator.com
More DNA Databases and Cold Searches
Monday, July 21st, 2008The L.A. Times has published another article on DNA databases, this time focusing on a researcher in Arizona who has found some evidence that nine-loci DNA matches may be much more common than FBI experts often state in court. This has led to calls for broader searches to see if the phenomenon is true in larger databases, such as the FBI’s CODIS.
The FBI is stonewalling, even threatening to bar states who consent to similar statistical searches of their own databases from accessing the national CODIS system.
Don’t rock the boat.We KNOW that DNA is infallible,90%of sex offenders do it again,pot makes you crazy,1 beer makes you a menace behind the wheel, breath tests are completely accurate and prohibition (both for drugs and alcohol) works.
Yeah, a long time ago the FBI claimed that you could tell, scientifically, whether someone was innocent of witchcraft by dunking them in a pond. If they drowned, they were innocent, but if they floated they were witches and had to be burned at the stake. It turned out their test wasn’t all that precise and it’s possible some of those burned at he stake may not have been witches.
Probably the same thing here with this DNA thing.
Of interest since the subject at hand is the FBI’s penchant for demanding an end to pesky efforts to get accountability from it…
http://techliberation.com/2008/07/08/the-fbi-and-politics/
http://techliberation.com/2008/07/08/great-moments-in-government-accountability/
http://techliberation.com/2008/07/07/the-more-things-change/
The BATFE notwithstanding, there is no agency that deserves more pure, unadulterated hatred from the American public than the FBI.
Cue Patterico’s post in 3, 2, 1….
Hmm Patterico does have a post up (and in fairness he did cover the last article so it isn’t that unusual that he is posting on it). However, this is a bit misleading on his part,
Yes, they botched the statistics, but they still got the right answer. This is a prime example of the fallacy fallacy and poisoning the well. Just because they got the statistics wrong (i.e. part of their argument) doesn’t mean that the conclusion in that article was wrong. The conclusion was correct, but their understanding of the rather technical side of the issue was badly misunderstood, just as many of Patterico’s commenters don’t understand the issue.
From the LA Times article,
Patterico thinks this is damning, however this strikes me as what happens with cold case hits. They take a profile, run it through the database and get a list of suspects on little more than DNA. Hence, they will get more hits than they would if they were say limiting by other factors (male, black, age, etc.). Granted after the fact they can then go back and rule out some of the people on that list (i.e. they weren’t alive when the crime happened, they weren’t in the area, etc.), but the point still remains that the DNA evidence, in terms of evidence in favor of guilt, isn’t anywhere near as powerful as DNA evidence in favor of innocence.
Most people think DNA evidence is a slam dunk. You got DNA evidence that matches a suspect well Hell lets just skip the trial and go right to the hanging phase. Especially if it is a crime that many would view as heinous (a child rapist, killer, etc.). To the extent that the article helps dispell this false belief it is a good thing, and Patterico’s whining is just silly.
Regarding the statistics of the situation, there is a valid point. This is a “birthday paradox” situation.
Here is the birthday paradox. Say you are in a room with 30 people. What are the odds that someone else in the room has the same birthday as you? A bit below 10%. What are the odds that some pair of two people in the room have the same birthday? Close to 100%.
(Not that this justifies the data stonewalling and threats here.)
I agree, that the FBI wont let the number crunchers crunch the numbers and provide the results is a serious blow to the integrity of the people at the FBI.
However, I don’t think that the research is meaningless or not important. The presence of people who are related or that more than one person could fit a profile (e.g. the Puckett case Radley discussed awhile ago). That the Troyer, et. al. research helps shed light on this and helps us better understand the issue is only a good thing.
Think the FBI DNA database is scary? Wait till they go full-speed ahead with their new national fingerprint database. You won’t have to be even so much as a suspect to find yourself included.
[...] More DNA Databases and Cold Searches. [...]
Barak, I agree, this looks like the birthday paradox to me too. Also, Troyer handled DNA profile matches in an unusual way that greatly increases the chance of a hit. I posted a long-winded explanation of it here: http://www.windypundit.com/archives/2008/07/something_fishy_about_dna_fing.html
But if that’s the case, if the science is good, I wonder why the FBI is fighting against these searches…