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."
Misuse Of Statistics (Score:5, Interesting)
Among other possible statistical mistakes, these unrealistically large numbers are based on the idea that each genetic location being compared is statistically independent. But in fact we know that to not be so. What we definitely do not know is how, or how often, many of these may actually depend on each other.
Let me give you a purely hypothetical example: what are the odds that a genetic profile from a random person contains a gene determining curly hair. What are the odds of finding this gene in a random sample?
You can answer this approximately by simply observing what percentage of the population has curly hair. Let's say 1/4 just for argument. So your odds are 1 in 4.
But here's the kicker question: what are the odds that a genetic profile includes a gene for curly hair, given that it also contains a gene for sicle cell anemia?
The odds are going to change drastically.
This is not a real example, of course, just illustrative. But one can easily see that the contents of genetic locations are NOT necessarily statistically independent, even if one of them does not directly cause the other.
We simply do not know enough to say that any two genetic locations are truly independent. Therefore these huge probabilities ("billions to one" for example) being spouted by prosecutors are completely specious.
Re:chimps have 97% of human DNA (Score:4, Interesting)
And that’s far from all. Imagine having a bone-marrow transplant. Now your blood has another DNA than your skin!
I remember reading about a person, who had three different types DNA in his body... at the same time!
DNA can be as easily faked as fingerprints. Hell, I could just “accidentially” cut a big politician, while getting his autograph. And then plant that DNA at a murder site. While I myself am completely sealed off in a virus-lab-style overall.
A overall that suffices will be below 50 bucks an a special store. And an autograph just is some travel costs. Everybody can do it.
Re:chimps have 97% of human DNA (Score:4, Interesting)
I am consistently horrified that juries offload their responsibility by blindly applying the judgement of expert witnesses (who are often paid to say the same thing over and over again), whether forensic scientists, psychologists or IT specialists. I take DNA evidence the same way as I take the contents of a third party /var/log: with a pound of salt, because I know it could have been planted.
When I was a juror I was interested in means, motive and opportunity as necessary but not sufficient conditions to vote guilty. I also made use of the defendant's inconsistencies in his testimony, details about the background of the defendant and victim to the extent that it was relevant to his alleged act, consistency of information from eye witnesses around the time of the event, known and unknown, doctors' reports, police officers, etc. I paid little attention to forensic details which might, according to the arguments of a scientist, help /confirm/ the prosecution's case, because I have more than reasonable doubt in my mind of any evidence which requires me to be an expert to interpret correctly - especially when I'm not that expert, instead deferring to some guy I just heard in a courtroom.
What exactly (Score:3, Interesting)
Are we talking about here? If this is a catalog of DNA of convicted criminals then it might be ok. But if its also DNA samples from other people who gave a sample to clear their name, then I don'yt think it should be made public.
Re:Misuse Of Statistics (Score:3, Interesting)
DNA also contains metagenes that control other genes, which means that DNA itself can and does change, so treating it like it's absolutely immutable is ridiculous.
It's not just the veracity of the DNA testing (Score:5, Interesting)
This giant number has the emotional effect of certainty, but that number is just the chances that the sample the DNA lab recieved corresponds to the DNA of the accused--IF NO MISTAKES WERE MADE and nobody is planting evidence or accepting bribes. It's not the chance that the accused is innocent. I'm sure this distinction is made in the verbal "fine print" but the jury will still be swayed. The giant odds numbers are nothing powerful emotional hooks. The real possibility that the DNA evidence does not finger the accused breaks down like this:
1:1billion the DNA matches someone else due to a flaw in the statistics of DNA testing
TIMES
1:$smallernumber the DNA lab has accepted a bribe, has a mole, made a mistake, etc
TIMES
1:$smallernumber the DNA lab has honestly received a sample from the accused but the sample was planted at the scene by police, the real criminal, or really bad luck.
The jury won't be considering these factors when they hear the "1:1billion" number. It's nothing but sensationalism.
Don't forget the human epigenome (Score:4, Interesting)
Re:chimps have 97% of human DNA (Score:4, Interesting)
Re:It's not just the veracity of the DNA testing (Score:1, Interesting)
The solution simple. Make it so that planting evidence is punishable by whatever the maximum the accused could have gotten for the prime is. So if a cop plants evidence in a capital murder case, he gets the death penalty. That should keep them honest.
Re:Anonymized? (Score:1, Interesting)
You do realize the DNA is PII, right?
Or did I just get wooshed?
How data would be misused (Score:3, Interesting)
Assume several thousand matches are found in the database. Defense lawyer will argue odds are in the thousands that the defendent was falsely matched. This is wrong. Much like the puzzle of how many people do you need to have at a party to have two with the same birthday (about 30, I believe). But the odds that two people have the same birthday are about 1 in 365 not 30/365 as would be falsely concluded using the same arguement as above.
Assume odds are 1 in 10,000,000 that two people have the same DNA profile. Then defense lawyers asks expert witness
"How many people would have to be in a stadium before the odds are greater than 50% that two have the same profile?
Witness "About 4400."
Of course the readers of slashdot would be excused from the jury by the defense as they would not fall for this.
Re:Misuse Of Statistics (Score:5, Interesting)
While true, this statement is yet another example from the trap of misleading statistics. Individually, your statement is likely true. However, collectively, for all the tests the FBI lab is likely doing, then it is likely false.
Look at it this way: "The probability of me, as a random individual, winning the lottery today is near zero." From this, it is tempting to conclude that: "no random individual in North America will win the lottery today." However, this is clearly not true. Multiple random strangers will almost certainly win the lottery today.
The statement "no random individual will win the lottery today" is false, because a huge number change occurred. There are millions of people in North America. A similar problem happens with the FBI genetic testing. They do a great deal of testing. Proving an individual test is likely correct is very different than proving large numbers of tests are all correct.
From a statistical analysis point of view, you would be better matching any given DNA profile against everyone else's in North America. Then you would know exactly how many random matches occurred, and if lab contamination occurred, because the sample would match the lab techs and the police officers DNA too. This is the test the FBI is arguing against. Nevertheless, this is the validation test that needs to be done, because modern PCR DNA techniques should detect significant numbers of people connected with the location and/or sample access path, over significant periods of time.
Re:chimps have 97% of human DNA (Score:1, Interesting)
So basically you're saying you believe witness testimony is more reliable than scientific evidence?
I simply can't work out how you read that message from my post. I was saying that the corroborating testimony of multiple witnesses is worth a lot, while the /interpretation/ of some scientific test by some guy (for all I know, as a non-forensic scientist) is worth very little.
The jury is not there as an expert in forensic science - indeed, in the United Kingdom, a forensics expert might be exempted from jury duty - and, as such, is not qualified to decide whether he is witnessing "scientific evidence". He must judge the reliability of the interpretation by the expert witness in the same way that you treat all other witnesses. You are making a very dangerous appeal to authority if you decide that, because one witness is announcing himself as having "scientifically verified" his data, he is more reliable.
A doctor is there in his capacity as a reporter of the injuries which he treated. A police officer is there to report on what he saw and what he was told, and we must judge his impartiality, his memory, etc. A forensic scientist employed by the prosecution, moreover, there is therefore no other reason than to say "I am here to assure you that this evidence shows this guy was guilty, and trust me because I'm a scientist". He should be viewed with at least as much doubt as the police officer, if not more, because the police officer does not play the "I know more than you - trust me" card.
Re:chimps have 97% of human DNA (Score:5, Interesting)
If the purpose is to independently evaluate the rate of false matches in a DNA database to be used in criminal investigations, what better database is there than the one that will be used for that purpose?
Privacy issues can easily be worked around here---there's no need for personally identifiable information (i.e., name or location, not the dna data itself :-P ) to accompany the database for this purpose. You might also worry about statistical independence between the sample to be used for the analysis and that used for testing the results, but there are very well established methods for using subsamples of a data set in just this way.
Re:chimps have 97% of human DNA (Score:5, Interesting)
I wouldn't call it a case of mission creep. Research is needed to confirm that the database is suitable for the purposes it was created for.
These issues were identified as early as 1969, in a landmark HEW report on computer records and the rights of citizens. It boils down to this: inferences drawn from data that affect the lives of people ought to be rationally justifiable. This means not using data until its suitability can be established. Mission creep can lead to data being used outside the context it is reliable in; but we can also run afoul of privacy and due process concerns by collecting data in the first place without establishing it means what he hope it means.
I've been concerned for years about the reasoning used in DNA screening. It entails a long chain of assumptions, and while all the assumptions *seem* plausible, the chance that one or more of them is wrong or has some unknown wrinkle is not negligible.
Re:chimps have 97% of human DNA (Score:3, Interesting)
Sorry, I meant “accidentially cut by the sheet of paper you hand him”.
But you are right, there are easier ways. It was just what I came up with first. :)
Re:chimps have 97% of human DNA (Score:4, Interesting)
Never mind that the forensic findings are (or ought to be) independently verifiable.
All worthwhile eyewitness accounts are independently verifiable, i.e. involve independent eyewitnesses. Don't let a commendable scientific spirit enter a pathologically obsessive state where you're happy to take a report of a complex scientific procedure as close to infallible but won't accept a dozen people in a park telling you that the grass is green and the snow is white because "eyewitnesses are notoriously unreliable" and "the grass and snow weren't observed under scientific conditions". Such disconnect has been parodied since Aristophanes, and for good reason.