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FBI Fights Testing For False DNA Matches
Posted by
timothy
on Sat Jul 19, 2008 10:06 PM
from the grassy-knollers-know-it's-easy-to-blame dept.
from the grassy-knollers-know-it's-easy-to-blame dept.
Statesman writes "The Los Angeles Times reports that an Arizona crime lab technician found two felons with remarkably similar genetic profiles, so similar that they would ordinarily be accepted in court as a match, but one felon was black and the other white. The FBI estimated the odds of unrelated people sharing those genetic markers to be as remote as 1 in 113 billion. Dozens of similar matches have been found, and these findings raise questions about the accuracy of the FBI's DNA statistics. Scientists and legal experts want to test the accuracy of official statistics using the nearly 6 million profiles in CODIS, the national system that includes most state and local databases. The FBI has tried to block distribution of the Arizona results and is blocking people from performing similar searches using CODIS. A legal fight is brewing over whether the nation's genetic databases ought to be opened to wider scrutiny. At stake is the credibility of the odds often cited in DNA cases, which can suggest an all but certain link between a suspect and a crime scene."
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well, well... (Score:5, Interesting)
What we're seeing here is a crack in the government's facade of fake-goodness. The ideas we're fed are that justice is blind, which means (we're taught), ultimately fair; that prosecutors and judges and the legal system in general have our best interests at heart, and so on, platitude after platitude...
But the truth peers 'round the corner here. They're not interested in accuracy, else they'd be all for determining how well this works, or not. The process and the results would both be open. What they're interested in are convictions, because that's how they keep score. That's how the public is keeping score.
This is unfair and irresponsible on two fronts. First, if you get the wrong person for any reason (including using DNA evidence that is supposed to be basically infallible, but is, in fact, fallible); then you've done a wrong to that person, of course. But secondly, for every false conviction the prosecutor and their accomplices notch into their pistols, the real criminal is now completely free -- the case is closed. They're not even looking.
As a society, we need to stop trying to raise up any part of the system based upon count of arrests, convictions, tickets, etc. The temptation to go for easy answers is too high; obviously, if the FBI itself is victim to this, an organization that prides itself on its organizational integrity, groups that have less tradition of trying to do right -- like the local cops who broke down your neighbors door last week -- are going to fall even more prey to such pressures.
As we see that the FBI tries to prevent the truth from coming out about a tool that is less effective than they claim, as they try to prevent exonerating information from reaching the defense, we see true colors.
These people are not our defenders; they claim to be, but they have their own agenda, and it is not about fairness. They're simply counting scalps.
This is why the death penalty is a bad idea. (Score:4, Insightful)
It is hard to believe the FBI won't do the study to get real numbers, but we've been here before. These are the same people who presented bullet lead evidence with equal certainty. The science is impressive but it means nothing when your original premise is wrong. In the bullet lead case, it turns out that matches were common and single boxes often had differences. The coincidence between two people is good reason to review the data and make sure DNA statistics are correct. Until that is done, the odds of DNA matches should be looked on with great skepticism.
It's screw ups like this that make the death penalty a bad idea. While life in prison is a terrible punishment, perhaps more cruel than death, it gives the state a chance to fix its mistakes.
Parent
Re:This is why the death penalty is a bad idea. (Score:5, Insightful)
It's screw ups like this that make the death penalty a bad idea. While life in prison is a terrible punishment, perhaps more cruel than death, it gives the state a chance to fix its mistakes.
Falsely sending a person to prison cannot be 'fixed', only perhaps ameliorated. The frequent unfunny jokes about homosexual rape in prison show that not only the conviction system is out of control, but the punishment system is as well.
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Re:This is why the death penalty is a bad idea. (Score:5, Insightful)
The findings in CODIS are truly staggering! While the odds of a false match are supposed to be only 1 in 113 BILLION, a search over only 65,000 records turned up 122 matches! About 1 in 533!!
That's not a little glitch or merely "surprising", that's the difference between a match meaning you are 100% the person who was there to you are one of the 7500 residents of a decent sized metro area who might have been there! Further, you're one in half a million in the U.S. who might have been there. One in 12 million worldwide.
It also means that every conviction ever made primarily on the strength of DNA evidence must now be reviewed and even re-tried if justice is at all a consideration.
While, given that this is a metric crapload of egg on the FBI's face, I can understand why they wouldn't want this to be true, if justice was anywhere at all within their objectives, they'd be all for further testing. They'd also want a moratorium on DNA based convictions while they sort this out.
The attempts by the FBI to explain this away based on the way the data was searched sound like desperation. They try to make it sound like this finding is an artifact of the search methodology rather than genuine collisions. They are right that this actually represents 4 billion searches, but even if so, that should provide a 1 in 25 chance of a single match according to the figures they claim. Instead, we have 122 matches. Calling those 4 billion comparisons searches is disingenuous however, any search on the Arizona database would be 65,000 comparisons.
Their rather heavy handed attempts to block all further research are simply inexcusable. It tells me that in spite of their weak excuses, they are well aware of just how damning this actually is.
The upshot of all of this is that DNA is best used as EXCLUSIONARY evidence. If you don't match, it wasn't you period. If you do, it MAY have been you. It's a good way to narrow down a list of suspects or even come up with a list to examine closer (it may or may not be enough by itself to be probable cause).
If there's additional evidence, it may add up to beyond reasonable doubt.
It bears repeating: If the FBI had any interest whatsoever in justice, they'd be the first to examine this more closely. If the DOJ had any interest in justice whatsoever, it would insist that they do it now.
Parent
Re:well, well... (Score:5, Funny)
but one felon was black and the other white
Well according to statistics it was clearly the black one
(note to mods, this is a joke)
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Re:well, well... (Score:5, Interesting)
Parent
Re:well, well... (Score:4, Informative)
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Re:well, well... (Score:4, Insightful)
I recommend you read a book like Sense and Nonsense About Crime and Drugs [amazon.com]. Our justice system is biased from the top down. For an example, the percentage of black and white drug users is exactly the same; last I read around 13%. However, a minority is more likely to be searched during routine police encounters by the police, more likely to be arrested, more likely to be tried, more likely to be convicted, and more likely to be sentenced to jail time. So, we go from equivalent percentages of black and white drug users to a wildly overrepresented percentage of black inmates on drug offenses; last I read 58%. Also consider that law enforcement often takes a "containment" approach to drug enforcement. To paraphrase a Chris Rock joke, if a 14 year old can score weed you think the cops don't know where the drug dealers are, too?
Parent
Re:well, well... (Score:5, Funny)
white guy: "I'm sparticus!"
white guy: "I'm sparticus!"
white guy: "I'm sparticus!"
white guy: "I'm sparticus!"
white guy: "I'm sparticus!"
black guy: "I'm sparticus!"
police officer: "That's the one, crucify him"
*How spartacus would have ended if the Romans were the LAPD*
Parent
Re:well, well... (Score:4, Interesting)
what is really shocking here, is that these 'matches' were being found in arizona, which has less than 2% of the Us population, unless a lot of other places outsource DNA testing to arizona it suggests that DNA fingerprints are little better than regular fingerprints.
TFA isn't very clear, except that she was working for the state of arizona when she noticed 'identical' matches.
some might suggest that some of the DNA used to identify criminals may have impacts on that persons likelihood to turn to crime.. but we really don't understand much of how the brain works or the effects of slight variations in dna on that.
Parent
Re:well, well... (Score:5, Informative)
If person A has a DNA profile that matches one other person in the country, it is still very strong evidence.
If upon checking the other states there was found to be an average of one matching person per state, 50 matches, still strong evidence, but not nearly so conclusive. Would now require stronger supporting evidence to be "beyond reasonable doubt".
If (prison population being approx 1%) there are found to be 100 matches per state, 5000 matches, then DNA becomes more useful as evidence for aquittal than for conviction, ie: non-matching still proves it wasn't you but matching doesn't prove it was you.
Parent
Re:well, well... (Score:5, Interesting)
Yes, but regular fingerprints are actually very good. That's why it's called "DNA fingerprints" and not "DNA shoeprints" or "DNA ballistics evidence".
Brandon Mayfield might disagree. Had he not been able to prove beyond a shadow of doubt (as in hundreds of eyewitnesses) that he was in Portland, Oregon when the FBI said he was killing people in Spain, he would have been in a peck of trouble.
Note the closing sentence of the following story: "an FBI fingerprint examiner told an expert hired by Mayfield the original print no longer exists".
Fancy that.
http://www.policeone.com/investigations/articles/88280-Newspaper-Faults-FBI-Examiner-in-Madrid-Bombing-Fingerprint-Case/ [policeone.com]
Note that it doesn't really matter whether the actual fingerprints were a perfect match or not. What matters is that the FBI lab said they were.
Parent
Re:well, well... (Score:4, Interesting)
Anyone with skill and with a true criminal mindset (as in, REAL criminals with an axe to grind) will be able to fool the feds. As far as I understand, they're no different than the KGB... they have to present a list of victims... AHEM... "apprehended criminals" in order to justify their existence.
Nothing new. They'll keep criminalizing innocent, harmless things and letting real criminals go. The prison industry is bigger than Chinese outsourcing, but you won't hear about it on CNN or even on the alternative news sites. Nobody wants to mention that outsourcing to China is no different in any aspect than outsourcing government furniture (just an example) to prison labor, which undercuts even the Chinese commies on price. Why do you think they are letting out violent felons while taking in white collar boys for shit crimes nobody cares about? Exactly... a violent felon is a liability to a budding industrial power (aka... the new forced labor camps called "corrections facilities"). A meek and easily subdued white collar boy, well he's easy to walk all over and he's afraid of his fellow inmates AND the guards. He'll do as he's told. Why risk angry violent felons incarcerated with the very profitable and nonviolent white collar "criminals" ?
Bingo. You've said it well chief, but missed the "profit" motive, which is what existed under communism, it existed under socialism, under fascism and in this fascist/socialist hybrid system that we have here in America. Nothing new... just different masks on the same old faces.
Parent
Re:well, well... (Score:5, Insightful)
Just wait until they start outsourcing prisons to China. Won't that be all kinds of fun?
God, I wish I were joking.
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Re:well, well... (Score:5, Insightful)
I've noticed something: government conspiracies always get modded up here and are usually based on "Think about it. You know it's true, man."
The reason overly pessimistic posts about the government get modded up and not overly optimistic ones seems to be that your average slashdotter is insecure and doesn't want to get lauged at for being naive.
Well call me naive, but I don't think things like this are driven by greed so much as incompetence, hubris, and an "us vs them" mindset.
Parent
Re:well, well... (Score:5, Insightful)
I do know where you're coming from, and I'd certainly hate to be considered a conspiracy nut. I do try to liberally apply the idiom "never attribute to malice what can be adequately explained by incompetence".
All that said, however, I'm not really seeing a reason here that can be explained by simple incompetence. If they are, at heart, good people, then they would want to know how accurate DNA results are. It wouldn't even expose them to looking bad if it turned out that they'd been using bad evidence - all they'd need to save face would be a photo of an FBI agent shaking hands with someone in a lab coat and a press release explaining how grateful they are for having this weakness in the testing system found. Any other ideas on why they'd want this not to be looked into?
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Re:well, well... (Score:5, Insightful)
Any other ideas on why they'd want this not to be looked into?
It's human nature not to want to admit mistakes, even to yourself. These people have spent years convicting people on DNA, and in the mind of the public it's rock solid -- if they have you on DNA, case closed.
The upheaval in the court system will be huge. All cases where DNA evidence was used will have to be retried. Throw in the mentality of "we know he's guilty anyways" based on other evidence, and it's not surprising that the FBI would rather sweep this under the carpet.
The idea that the FBI is part of some conspiracy to get slave labor is absurd.
Parent
We're seeing no such thing. (Score:5, Interesting)
What we're seeing is a consequence of basic math.
1/113 billion chance a particular person has the same DNA profile as me. 6 million records. So I have a 6 million / 113 billion chance of matching someone else in the database. Drop some zeros and thats 6/113,000. Of course, each of the 6 million people in the database has a the same chance of matching someone - so that's 6/113,000*6,000,000 - which means there should be 318 people who match someone else in CODIS, or 159 'matches'.
# of people matching = size of group * size of group * chance of match
Anytime you have something that has a small chance of matching, but a fairly large sampling group, your chances of matching are high, because your chances of a match existing within the group is the SQUARE of the group size.
So it would be surprising if there were NOT people who matched in CODIS. The question is, are there more or less that 318 of them, and how much more or less?
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Re:We're seeing no such thing. (Score:5, Insightful)
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Birthday Paradox (Score:4, Informative)
If I'm not mistaken, what you've described is the Birthday Paradox:
http://en.wikipedia.org/wiki/Birthday_paradox/ [wikipedia.org]
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Re:Birthday Paradox (Score:5, Informative)
If I'm not mistaken, what you've described is the Birthday Paradox:
http://en.wikipedia.org/wiki/Birthday_paradox/ [wikipedia.org]
You aren't mistaken, but the Wikipedia reference is actually Birthday problem [wikipedia.org].
Parent
Re:We're seeing no such thing. (Score:5, Insightful)
So what you are saying is that a new sample has a 1 in 19,000 chance (6e6/1.13e11) of finding a match in CODIS at random, even though this is a new sample not present in the database. With thousands of police departments nationwide running samples against CODIS every week, false matches like this may occur frequently. If the consequence is that an innocent person is charged or even convicted of rape or murder, this is frightening.
There is a big difference between telling a lay jury "this match had a one in a 113 billion chance of occurring at random" versus "this is an event that occurs randomly on a routine basis." Non-statisticians have a hard time getting their head around the concept of correction for multiple hypothesis testing.
The real problem is that the FBI match criteria were developed years ago when the CODIS database was small compared to its current size, and these criteria have not been updated in light of growth in the database and new technology. Using state-of-the-art genotyping technology, it should be possible to design a test with a small chance of a false positive match even if the database contained the entire US population.
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Re:We're seeing no such thing. (Score:5, Informative)
>>There is a big difference between telling a lay jury "this match had a one in a 113 billion chance of occurring at random" versus "this is an event that occurs randomly on a routine basis." Non-statisticians have a hard time getting their head around the concept of correction for multiple hypothesis testing.
To give an apocryphal quote by Mark Twain: "People use statistics the same way drunks use lampposts - for support, not illumination."
The lack of ability to reason statistically is extremely common in America. I mean extremely common - even in grad students publishing papers on stats, or in the technologically literate crowd. I'd used to write examples of egregiously bad stats in my livejournal in papers and news reports, but gave up because it was so common.
The DNA testing example is actually an example we studied in the Bayseian/conditional chapter of my stats textbook. It described an actual court case in LA where I got was convicted solely by DNA evidence (there was no other evidence to convict him, and he wasn't lucky enough to have an alibi) because the prosecutor confused the odds that (in this case) the odds of the match randomly matching being only one-in-a-million, and those are some pretty powerful odds. Of course, that would mean that in LA alone, there would be 6 people (on average) matching the DNA, and so the chance of the guy being guilty is actually only 1/6 or so.
The problem I have with the DNA "this has a one in 113 billion chance of matching" is that this is an extrapolated number based on certain premises of independence between the different loci. Whereas the more we learn about DNA, the more we learn that there is a high degree of covariability, certainly enough that (as the article shows), the odds of a match are actually much much higher.
Parent
Re:We're seeing no such thing. (Score:5, Interesting)
It's probably even worse than the naive math indicates, because odds are not everybody involved will actually be unrelated in the mathematical sense anymore.
On the other hand... as others point out, in the birthday paradox there's a huge difference between two people have the same birthday and someone has the same birthday as me. However, in a prosecution situation, it is the latter that matters, not the former. Simply showing that the birthday paradox applies doesn't really prove that for a given criminal, that the odds are high that the match is a false positive.
This is also why government attempts (by well meaning people) to simple run dragnets over large datasets looking for "bad people" need to be resisted; while the birthday paradox is not always in play, similar statistical effects can be found in many other situations that cause enormous amounts of false positives. "Due process", where we investigate someone with all available tools only after we already have good reason to suspect them (to simplify, of course), turns out to be important not just for our rights in the abstract, but statistically sound, as well.
At the risk of potentially defending the government (pause for the shocked intake of breath), I find it quite plausible that the government knows all of this, and is resisting this investigation because they do not look forward to explaining this to every jury unto the end of time. While I support open disclosure and letting the chips fall where they may as a matter of principle, if you take a moment to look at this from their point of view, even if you dare take the step of assuming they're not actually out to get you personally (pause for another shocked breath), you might find it hard to avoid having a little sympathy for their position. (If you're still having a hard time, engage the "Most jury members sure are dumb, ha-ha!" cynicism circuit and consider the implications.)
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Re:I wonder... (Score:4, Informative)
. That is to say, the chance of having marker A might be 1% and the chance of having marker B might be 5%, but the chance of having BOTH might very well be higher (or lower) than .05%.
IANAFG (I am not a forensic geneticist) but the co-segregation of genetic markers is such a fundamental and well understood process that I would have a hard time believing that they wouldn't know and correct for the rates of their chosen set when calculating the probabilities of a matched set.
Of course the statistics they calculate are probably based on estimates of pairwise segregation. Some higher-order effects may be at work that change the statistics relative to a basic model like independent pairwise segregation.
For example, allele A of gene 1 and allele B of gene 2 may not segregate according to a previously measured pairwise stastistic in the presence of allele C of gene 3. Such higher-order effects may have a significant impact on the statistics but would require a *lot* of data to reveal.
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Re:I wonder... (Score:4, Insightful)
I would have a hard time believing that they wouldn't know and correct for the rates of their chosen set when calculating the probabilities of a matched set.
And I would have a hard time believing that the prosecution gives a damn whether what they present is accurate as long as they can get the conviction. I have yet to see a prosecutor in real life who's more concerned with finding the truth than getting the conviction.
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Re:We're seeing no such thing. (Score:4, Informative)
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Re:We're seeing no such thing. (Score:5, Interesting)
Well, maybe not.
From the article, the real issue appears to be that they make the assumption that the markers are independent of each other without having done the research.
In fact, they should know better than that. From DNA as a forensic instrument [columbia.edu]:
If the markers were truly independent, the polymorphic variants mentioned would be random as well.
So if the above is true, the markers aren't independent and they know it.
Parent
Re:well, well... (Score:5, Interesting)
I have seen first hand how the justice system truly works. Back in my youth I was a bit of a delinquent, and was convicted of many fairly petty crimes, mostly misdemeanor but nothing worse than a gross misdemeanor. I freely admit that I was usually guilty as charged, and I took my licks, but there were two cases where I was absolutely innocent.
Part of their strategy is to charge you with everything in the book, that way when plea bargaining comes around they can act like they are doing you a favor by dropping the extraneous charges if you plead to the main charge. The prosecutor had absolutely no interest in justice and wasn't interested in explanations or evidence, it was made very clear that if I refused to plead guilty it was going to cost me. In retrospect i'm confident I would have won both cases had I gone to trial, but the scare tactics can be quite effective, especially on a 20 year old kid.
I accepted the plea bargain in both cases to stay out of jail and avoid a costly trial and missing more work. Being innocent is just as costly as being guilty. Ironically I had to tell the judge under oath that I was really guilty and wasn't just saying so for the sake of the plea bargain. The convictions went on my permanent record and I got some hefty fines and probation, and the prosecutor got 2 more notches on her holster. 8 years later these convictions in particular, which were gross misdemeanors, cost me a very nice job.
Like I said, it was fairly petty and doesn't compare with the innocent people who are rotting in prison right now, but I can definitely sympathize. We see it all the time, people pleading guilty to avoid the death penalty or long prison sentences. When it is more of a punishment to prove your innocence than it is to plead guilty, something is wrong with the system.
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Re:well, well... (Score:5, Insightful)
There's a difference. A prosecutor in the situation you give is placing his own career interests above the interests of justice and the law.
A defense lawyer getting someone off "on a technicality" is at the very least demonstrating an allegiance to the letter of the law and a commitment to see that all people are treated under the law equally... and often may be the last line of defense against a government bent on violating civil rights.
There's really no such thing as "getting off on a technicality." Whenever you hear that phrase it's coming from a prosecutor or police officer who at the least didn't do their job properly and at worst violated the law themselves, and got caught.
When the police searched you illegally, you "got off on a technicality."
When they came into your home without a warrant, you "got off on a technicality."
When they didn't properly document and control the chain of possession of evidence used to convict you, thus throwing into doubt whether it's even legitimate evidence, you "got off on a technicality."
When they interrogated you improperly or otherwise throw into question the accuracy of what they claim is your testimony to police, you "got off on a technicality."
When they selectively show your photo to or otherwise lead the victim into presupposing you are the guy who did it, you "got off on a technicality."
When the prosecutor has withheld information that might have exonerated you or changed a jury's verdict, you "got off on a technicality."
"Got off on a technicality" = not guilty.
Parent
Re:well, well... (Score:5, Insightful)
"If they truly cared about justice they'd say "hey we need to take another look at this". I don't know how they can live with that on their conscience anymore than I understand how defense lawyers can live with setting rapists and killers free on technicalities."
There's a difference. A prosecutor in the situation you give is placing his own career interests above the interests of justice and the law.
No, no, no. Three words explain why the prosecutor doesn't want to re-try the case and why this is the right thing to do in the circumstances: adversarial justice system.
It may not be the best system, but it's what we have; it is the duty of the prosecution to assume that they are right, just as it is the duty of the defence to assume that the prosecution is wrong. To allow the prosecutor to pick and choose the circumstances in which to present a strong case vs the circumstances in which to side with the defence introduces more bias into the system. Each side must present their case as if it was absolutely the way that they say it is, and then the jury must weigh the circumstances and decide.
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Re:well, well... (Score:4, Insightful)
The situations I'm talking about are not those. A prosecutor that withholds evidence he knows may be exculpatory is not a prosecutor assuming he is right - that's a prosecutor being corrupt.
The examples I gave are not examples of the adversarial justice system.
They are examples of civil rights violations. They are examples of unethical behavior. They are examples of government corruption. They are examples of crimes.
A prosecutor fighting retrial over a disagreement over the validity of evidence is an example of the adversarial justice system.
A prosecutor fighting retrial over evidence they improperly and knowingly withheld is not - it's an example of a criminal trying to cover up his crime.
Prosecutors and police are not always simply motivated by doing their jobs properly. They, like other people, are also motivated by greed, personal ambition, prejudice, personality flaws.
"The Authorities" lie and break the law. Not rarely - routinely.
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Re:well, well... (Score:5, Insightful)
I think the answer is that most lawyers in general lack a conscience, you'd have to to be successful.
Disclaimer: my bar exam is a week from Tuesday.
I've had this conversation with people before, its why I want to stay out of criminal work. I guess the theory is that you throw everything on the table and hope that the opposing attorney is doing their job. That's the adversarial system. The Constitution dictates that the prosecution has to throw a lot more on the table. Ethics rules dictate that the prosecution also has to defeat their own case when they have information that will damage it. The defense attorney just has to do the best he can with the facts he is given.
Its easy to malign both sides of the system. However, neither is an easy task. The prosecution is ethically responsible for both society's interest, and to some extant, the defendant's as well. The defense attorney is responsible for the defendant's interest but, to a broader extent, society's interests as well. Defense attorneys protect even you and me in the sense that those accused of crimes, whether innocent or guilty, set the periphery of our legal protections. Guilty people have been responsible for the liberties you and I enjoy because they challenged the procedure, actions, and level of proof employed by the government. Whether or not an attorney is scum or devoid of conscience, there is an attorney on the other side taking them to task. Sure its an imperfect system, but its the best society can come up with and we muddle through.
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Re:Convictions instead of Science? (Score:4, Interesting)
"We have to refocus everyone on the Rights of the Innocent"
No, we need to focus on rights and fairness, period. Cops aren't always truthful. Drug dealers sometimes don't lie.
Renaming basic human rights and due process, i.e. Rights of the Innocent, to some special "needs" category plays into special interest. Much like how "victim rights" laws throw to the wind fair court cases; the defense has their name thrown in multitude of papers and intense scrutiny, while the victim hides in anonymity. This has resulted in inequities in handling of cases--this become hugely apparant in both the Duke rape case and the Kobe Bryant rape case; consider these were big name cases where the flaws were apparant and utilized by the prosecution. (If you're wondering what should happen--if the victim's name is protectd in a case, the defense's name should also be protected in the case.)
Furthermore, such new terminology often is at some point redefined and abused--most of the citizens of the United States still don't realize that "violent" offenses constitute mere drug use or sex (so called statutory rape) under the 1984 Bail Reform Act (this is why California's 3 strikes laws ends up taking in so many repeat offenders). I can easily see "rights of the innocent" laws being ineffective and creating a special class as one-time DUI offenders now accused of murder get denied a "special class" of rights.
The facts are rather simple--for the past 60 years, laws have gone overly pro-prosecution. Part of this is government keepign score, as someone else put it. Part of this is also on the general public for being stupid, scared, and greedy--why people will look less horrified at a murderer than a pet killer, or if they see someone shackled they presume guilt, or see some sick social advantage in another person being locked up (prison doors open as the economy tanks means more jobs for the "innocent" sort of thinking).
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DNA can disprove only (Score:5, Insightful)
Unless the crime labs start encoding the full DNA sequence, even then identical twins will duplicate, the best DNA, for that matter finger prints, can do is prove it is *NOT* that person.
Re:DNA can disprove only (Score:5, Informative)
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Transparent government (Score:5, Interesting)
Please support radical transparency [wikipedia.org] and open source the government [wikipedia.org].
If everything is out in the open, there can be no hiding.
Re:Transparent government (Score:5, Funny)
Everything, I suppose, but your nic.
Parent
So, the 1:113 Billion estimate is wrong (Score:4, Insightful)
Questions:
1) How wrong is it?
2) Why is it wrong?
3) Who is responsible for this blunder?
Quite possibley this can kill DNA evidence. Somebody was more interested in convictions than the truth here. Despicable.
Re:So, the 1:113 Billion estimate is wrong (Score:5, Informative)
Have a read. It shows that you can't trust statistics when you only have half of the picture, and why it can be so dangerous to do so.
Parent
Re:So, the 1:113 Billion estimate is wrong (Score:4, Insightful)
Even though the odds of sharing a birthday with a random person are about 1/365, if you have 23 people in a room, you are likely to have at least one "birthday" match. With about 60 people, it's almost a certainty.
A back-of-the-envelope calculation gives me about half a million as the number of DNA samples required to give a 50/50 chance of having two people with matching DNA samples... but I might have messed up on that.
Parent
An example of the birthday problem (Score:5, Insightful)
From the description, this seems like an example of the birthday problem [wikipedia.org]. Briefly, in a group of 23 people the odds are 50-50 that two of them will have the same birthday, while in a group of 57 the odds are better than 99%. However, the odds that someone in the first group will share *your* birthday are far less, roughly 6.1%. Quoting the Wikipedia article, "For a greater than 50% chance that one person in a roomful of n people has the same birthday as you, n would need to be at least 253. Note that this number is significantly higher than 365/2 = 182.5: the reason is that it is likely that there are some birthday matches among the other people in the room."
Likewise, the odds of there being two people with matching DNA in a database are far higher than the odds of someone else matching *your* DNA. So it seems possible that the FBI could be quoting accurate odds, while at the same time there being lots of matches within the database.
very worrysome (Score:5, Interesting)
As an American once arrested by the SS/FBI for computer related crime a while ago, DNA testing always worried me. I can understand it for violent offenders (which is how it was started and then carried over to all felons).
I can also tell you, if you refuse to submit to testing, they give you what they call "diesel therapy," taking you away from the cushy club fed camp you were in and busing you around the system until you relent. If you were given a half way house sentence or probation, they can revoke either for not submitting a sample.
Dispite turning my life around, finishing my degree and now working as a developer for a medium-size firm, I worry at times that one night I'll be hauled away because some flunky at the FBI mixed up DNA samples or didn't compare them correctly. I can imagine this being a horror scenario for anyone who's never broken the law, but can anyone imagine there being even a slight chance a bunch of narrow minded, non-technical cops are going to believe me, even if the crime is something totally unrelated to my history?
Birthday paradox (Score:5, Informative)
Practical truths... (Score:5, Interesting)
Irrelevant (Score:4, Funny)
And this is relevant how? You've already told us they were distinct people, this doesn't make them more distinct.
Re:False matches my ass. (Score:4, Interesting)
if that's true why bother suppressing it and just let the do the comparisons. It'd be easy enough to bury them in regular scientific testing since the database would show that the hypothesis of these researchers is blatantly wrong and the only time being wasted is their time and not the FBI's.
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Re:False matches my ass. (Score:5, Insightful)
There has never yet been a 13-locus match seen between unrelated people in the national database- despite the 5 million or so profiles currently in it. I'm sure the average Slashdot reader can manage to work out how many pairwise comparisons that is. (Hint- it's a pretty fucking big number.)
Well it seems that your statement of 'never' is simply because that comparison has not been run, since the FBI is doing everything possible to prevent testing of that theory. If its so unimaginably rare, it would seem that the FBI would be all for doing these searches to bolster the value of their evidence. However the results in MD would seem to challenge that dogma.
A 9-locus match between unrelated people is not surprising. That's why we don't sue only 9 loci, idiots!
Well it seems that California prosecutors are idiots and were using a 9 locus match to prosecute a man for a 2 decade old murder. From TFA: "Its implications became clear as she prepared to defend a client accused of a 20-year-old rape and murder. A database search had found a nine-locus match between his DNA profile and semen found in the victim's body. Based on FBI estimates, the prosecutor said the odds of a coincidental match were as remote as 1 in 108 trillion." So just to explain why we 'idiots' would use a 9 locus match: DNA collected at a crime scene is not a complete genome. Often it is only fragments. You may not have a full 13 loci to check because the fragment you have would not cover all 13 loci. There is, however a statistical nicety here that you've completely side-stepped in your haste to call us morons (which TFA mentions). The likelihood of finding matches of 9 of the 9 you have in your genome fragment is far less than the likelihood of finding any two people in a database with 9 of any 9 of 13 loci that match.
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Re:False matches my ass. (Score:5, Interesting)
I match 12 out of 12 Y-DNA markers with 9 other people who have had their DNA tested. Based on our last names, none of us are related.
I don't think you should be able to use blind searches of a DNA database as evidence, because it's too easy to get false positives. It's only useful evidence against someone you've already found by other means, or as a way to generate leads.
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Re:You're all missing the point! (Score:4, Funny)
You're making the mistake that racists use logic.
They'd probably say the black guy stole the DNA.
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