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Are Fingerprints Unique?
MattJ writes "There's an incredible article in LinguaFranca about fingerprints. Maybe they're not all unique after all. And maybe those fingerprint experts are not much more scientific than handwriting experts. Fascinating details."
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kinda like Bush and Gore...
To guestimate, I suspect the real numbers are about 10^12:1 false matches, which is quite alarming, if there are 10^7 entries, one in 10,000 will be a false hit with someone totally at random. The false negative rate is probably closer to 1% and might be as high as 10%.
Does anyone have better numbers, after all, I'm just guessing at this point.
--Mike--
Puddin' Head Wilson was wrong. Bad Mark Twain!
The Blaster Master Fighting for Truth, Justice, and Evil Pie since 1979
Well fingerprints although not unique as we once though still provide good evidence. I remeber reading somewere that about 1 in 10,000 people have similar fingerprints. they still would be crucial evidence if the over 100 people with the same fingerprints in the country never set foot in the city.
Great. We're trusting a multi-variable analytical computer system that's as old as Pac Man... Especially considering that:
and
I could just picture the conversation in the lab at Lockheed International Conglomerate:
"Richard, I've been thinking...what about distortion from pressure on either the latent print or the test print, or both!" "Oh Sam, you know we only have 640KB of RAM to do our matrix multiplications in...and besides, the government's paying us a lot for this. We're gonna have one hell of a Christmas bonus..."
Consider this, too:
Great, they may as well be dowsing for water wells now... Okay, I bet $10 that the feebs' computer (AFIS) is a total fraud. The burden of proof, however, is on you...
This sucks. I'm going back to bed.
In 1999, marijuana killed 0 Americans...
Ewige Blumenkraft!
There is never any proof that is 100% watertight
Oh yeah? Prove it, smart boy!
The software is available (in every police station), the data is available (also in the police stations) -- let's just see what the percentage of cases where the programs claim that the figureprints of two different people are the same.
Uh.... if i take your assumption of 1 in 10,000 people having similiar fingerprints, lets start assuming...
,Liechtenstein(32,207), or Bangladesh(129,194,224). But you may be referring to Botswana(1,576,470), or Estonia(1,431,471), or Swaziland(1,083,289). Or go to http://www.infoplease.com/ipa/A0004389.html to find out for yourself.
a) That's 7,322,564 people in New York,NY (1990 US Census) with a rate of 1/10,000 gives approx. 732 similiar ones give or take a variance of 1/x^2, whatever x being. Maybe as many as 1000, as few as 500.
b) That's further assuming we discount all the transient workers coming into town & all the tourists. Which may double the population on a given day. A population doubling due to this would not just double the "similiar score" to 1464, but would be something on the order of, hmm... 732^2, or 535824. Wow.. half a million, because this is combinitorial. Suzie Q182 matches 1464 other fingers, and each of those 1464 other fingers have thier own set of 1464 matches, but not with 100% overlap. False positives tend to blow up.
In fact, you could prove that someone out there has two fingers that are similiar to another persons singular digit. I'm not sure how to finagle the numbers to find out if the two fingers would be rated as similiar or dissimiliar. There probly is a secondary rate preventing a person from having two matching fingers.
Now for some more fun, you give the assumption that "if the over 100 people with the same fingerprints in the country never set foot in the city" to determine what country your talking about. (all figures are Bistro-Math(tm), please don't nitpick, instead create your own cosmology)
100 people times 10,000 is 1 million plus a bit for the guy with the finger that lives in the town. Well, you don't live in Albania(3,490,435)
Basically, a rate of 1/10,000 is scientifically un exceptable. And since there is no "rate" since all mistakes are due to technician error, not error in the system (can you say Cult?) there is no way for it to be a science.
USA-Democracy is 270 million YESes and NOes a day, not one every four years.
The attempt to prove that a non-existant creature does not exist is what is known as an unfalsifiable statement. There is no possible way to prove that a non-existent being does not exist.
The correct approach in science and in philosophy is to start with a falsifiable statement (such as "Unicorns exist"). The more scientists and philosophers search for evidence of the existence of unicorns and fail, the more likely it becomes that unicorns do not exist.
have a day,
-l
I needed to be fingerprinted before they would give me my green card, what fascinated me was this machine they took my fingerprints on.
At first glance it looks like a photocopier gone haywire, with a largish monitor. This is where your fingerprint image gets projected. There are several squares of different sizes, and they look similar to the glass partition of an everyday photocopier.
No ink involved, He just asked me to lightly place my fingers on the glass, and he held my fingers at some points to keep them from jiggling (he was very exacting about it).
When he was satisfied, he brought the images of my prints up on the screen in front of us. He remarked "Well, no life of crime for you". He was referring to the fact that I had "excellent patterning". He remarked that "You have excellently defined fingertips" etc. etc. He then showed me the neatest thing he magnified my prints to the point that he could COUNT the skin pores between the whorls of my thumbprint
Actually I was impressed, since up til that point it had always involved me getting my fingers full of that stupid ink and having to roll them around on a piece of paper. That machine was much cooler.
And for the record, I don't have one :)
spam, spam, spam, spam, e-mail, news and spam.
Folks, rememeber the OJ trial? There we saw DNA evidience, based on modern science, with proven error rates and a far lower possibility of subjective reading, being totally rejected as forensic evidence. And yet, many people are locked up every day on the basis of fingerprint evidence, based on 19th century science, with unproven error rates and based entirely on subjective judgement.
Does anyone else see a double standard here? And how can we help society to make better, objective scientific judgements, rather than just listening to demagogues?
Information doesn't want to be anthropomorphized. -AC
And I just found two identical snowflakes yesterday too!
No two fingerprints the same? Weeeeell... let's not get carried away here.
The (extremely valid) point here is not that fingerprinting isn't useful, but that it is by no means an infallible method. If you have a suspect and their prints could not POSSIBLY match the ones from the crime scene, then you can be pretty sure this isn't your man. However, to say that the main structure of the ridges of the two prints is exactly the same, that some of the secondary characteristics match, and that overall this is without a doubt a match.... that's kind of sketchy.
Developmental biology is far from the nice, linear-type science the public seems to believe it is... Certain attributes of the organism at any stage of it's development can be approximated, but it's not always as simple as "gene X is present, so phenotype (trait) Y will be expressed". The future of the "designer baby" where parents could pick and choose their child's characteristics is far, far in the future (even then it wouldn't be exact). Why? Because... genes are like a set of very general rules... it's chaos theory at it's finest. Here is a system that obviously has some underlying order (to produce an organism with 2 eyes, antennae, whatever), but even barring gross mutation, prediction of the final results of an organism's development is still (at this point) an estimate, at best.
It would be impossible to say exactly how many hairs a mouse would have, their precise location, and what color each would be by only looking at the genes of the creature. There's innumerable chances for deviation. You can stick two similarly colored mice together and say; "these mice are similar", but until you had an exact, infallible catalog of every minute detail of the organism, you would have no empirical (scientific) basis for saying how similar they are, or even "these mice are exactly alike". Even exactly the same genes (identical twins/clones) produce different results if you look closely enough.
BUT... that's a far cry from an objective justification for the impossibility of 'lighting striking the same place twice';P. The same 'proof' was used when "they" once said that no two snowflakes are exactly alike. Whiiiich... after someone did some serious, scientific researcg on the matter, later turned out to be bullshit;). Much in the same vein, "the identical twins had different prints" argument means jack; two people could have different sets of genes in respect to their fingerprints, exist in different environments, and it's still not impossible that they would end up with extremely similar (or even indistinguishable) fingerprints. There's a quite a few people in the world; see "Europeans descended from 10 males" a few days back... even though America's a large place, those ancestors have passed on a little bit to everyone with caucasian ancestry - that's a lot of people with the same daddies/similar genes;). Is it that hard to imagine that, even though the odds are extremely small, that two sets of prints, taken right off the two specimen's fingers, could be similar to the point that they would appear exact?
Now for the coup-de-gras... the fingerprints in crime scenes aren't lifted straight off someone's fingers in a controlled manner. There isn't some fingerprinting technician dipping the criminals fingers in grease and carefully applying them to the doorknob or whatever. As mentioned, smudging, processing, and method of extraction result in very loosely defined fingerprint specimens. Is it crazy to think that you can, 100% of the time, say with 100% certainty that "These fingerprints belong to this individual"? You bet. Should fingerprinting be forgotten, then? No, it's still useful, but... I think the courts have led people to believe that fingerprints are the end-all-be-all of forensic evidence. If America's going to claim that it's judicial system operates by "innocent 'till proven guitly", we might as well make the extra effort to make sure that the methods that we use to prove someone guilty are as sound as possible, or the system quickly becomes a farce.
Life: a sexually trasmitted disease that has a 0% survival rate.
Here's how it works. The statement "All crows are black" is logically equivalent to the statement "All non-black objects are non-crows."
So, assuming there's a finite universe of objects -- take that one up with the cosmologists -- I can estimate the probability that there exists a non-black object that is, in fact, a crow, simply by counting non-black objects, and looking to see crows among them. A good place to start is out on my lawn; I'll go through and see if any of the green objects sprouting from the soil out there is a crow.
Nope: they're all weeds...I mean, blades of grass. That's still more evidence for the thesis that all crows are black.
To carry this through to your thesis that there are no unicorns, the statement "There are no unicorns" is logically equivalent to "All objects are 'non-unicorns'". I can't acquire any evidence of the first one directly, but I can provide evidence of the second.
Even if you accept this figure of one in 64 billion the birthday paradox predicts that you can expect to find an identical pair of fingerprints in a database of sqrt(64e9) fingerprints which is just a little over 250,000. I believe the FBI fingerprint database is significantly larger than that. After this "threshold" of sqrt(N) is crossed the number of duplicates starts to rise quite sharply as the database size increases.
----
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
Did you forget to read the article? He never concludes that fingerprints can be the same instead he concludes with the judge disallowing testimony about the validity of fingerprinting's validity.
Think of all of the tens of thousands, if not millions of cases that would have to be looked at again if it were happen. The resources for that simply don't exist.
Rich...
Ignore Alien Orders
I may be missing something here, but it would seem that there must be millions of points where fingerprints could be similar. Yet most police forces are prepared to accept 8, 10, or twelve points of similarity as being conclusive. If so then there, by coralllary, must be millions of points that are dissimilar. It would seem, in fairness, that the courts, or at least defence lwyers, should be looking for dissimilar points not similar ones. If there are six milion possibilities and I only match nine and am convicted it would seem that justice is a joke. So what's new?
That's the point of the article -- we don't really know those odds, as all the popular numbers seem to have been created mostly by guessing.
This is easily verified with standard scientific practices. Grab 10,000 people and give them a metal ball and have them handle it for awhile (without telling them why), then grab clear fingerprint impressions. Give the balls to examiners whose job it is to grab as many fingerprint impressions as they can. Put all this into a database, then start pulling out fingerprints and having examiners match them up.
What is the error rate whereby fingerprints were matched incorrectly?
As I see it, the real problem is that people can only think in black or white. The focus of this little question has been if fingerprints are unique or not. The average person isn't mentally equiped to think in terms of "How unique are they?", a vast grey area. Science can never answer black-vs-white questions, but they can certainly measure grey.
Do paper cuts (especially big cuts) change the finger patterns? Just curious... :)
Ant(Dude) @ Quality Foraged Links (AQFL.net) & The Ant Farm (antfarm.ma.cx / antfarm.home.dhs.org).
Our legal system is more and more trying to use gorge jetson way of dealing with their problems. They don't like explaining that they think a person is guilty. They want to say we found the prints we feed them in to the computer and our can the name of the defendant. Fingerprints don't lie and so he must be the one. This is wrong on many levels first My prints on a weapon says I may have touched it not that I killed anyone. Example I read where the FBI arrested a woman because a threat letter with "her prints" was sent to the Israeli embassy. All she had to do was load the printer or copier but that does not matter. It was found that she in fact was set up. But the embassy sent the letter to the FBI and the but it in there system and here name came out. When you think of it, it is very easy to frame some one this way. Second Partial fingerprints are just like other partial fingerprints. The pressure on FPE to get a name to spit out is huge. The FBI collects Fingerprints by the 100's of millions and one day you may find that it is your name the computer spits out. The reason FPE believe that they are full proof is because they what and even need to believe they are. As long as the system is believed to be full proof and once the computer spits out a name very little effort is put into finding any one else that may have done it. Push button police work is not good. But as long as the system can get away with it it is what we will get. Dont let any one have your prints if you can help it.
The problem isn't whether fingerprints are unique (although it's an interesting point that their uniqueness has never been proved). For all the author cares, they are unique. It's irrelevent to his chief argument.
The problem is that exact complete fingerprints aren't used in forensic investigation. Mere fragments are. And not just fragments; sloppy fragments, read by making impressions with the detective's dust and transfered onto paper. The question is therefore whether those fragments are unique relative to other fragments, given the additional fudge factor in how they're read, and whether the use of fragments instead of complete fingerprints is sufficient.
People need to work on their critical-reading skills.
-- Anne Marie
Suppose that there are N objects in the universe, and I've observed none of them. What's the probability that at least one of them is a unicorn? Well, given that I know nothing about the relative likelihood of Unicorn-ness among objects, the most likely a priori estimate of the likelihood of a Unicorn is given by quantifying across all possible predicates on the Universe, and computing the probability that IsAUnicorn(x) is true for some x. (After all, the IsAUnicorn predicate is just another predicate. I don't know its characteristic function, but it's got one.) Then it's easy: the Universe is finite, and so there are only finitely many predicates on it, and (drumroll please)...exactly one of those predicates has no elements!
So, our estimate of the probability that there exists at least one Unicorn, given that we have no evidence speaking to the question, either way, is 1 - 2^(-N), where N is the number of objects in the Universe. Thus, it is very, very likely that there exists a Unicorn, in default of any evidence -- but it is not quite certain.
o i thought it were
out of sight out of mind
of course under the new Moron administration itll be
what, me worry?
yours wdk
Bill Kurtis pointed out the other night that in California, a false witness in a capital trial faces a capital trial of his own. But of course the racist LA prosecutors would never bother to charge a fellow good white racist cop for framing (or at least buffing up the evidence against) an uppity rich nigger, never mind set him up for death.
Kurtis tried to play it as though it made conspiracy unlikely. But conspiracy was not necessary for the evidence tampering. The only conspiracy on the prosecution of the Simpson was an amalgam of inflated egos.
I was amazed they were so cocksure as to try him for both murders together... they should've kept one in reserve in case they f*cked up like they did. Then they whiningly blame the jury, who they'd approved. But the jury did its job: there was lots of room for reasonable doubt, especially (to me) in the vaunted "scientific" evidence... to drag this back to the topic at hand.
As I understood what was presented... I refused to watch the trial voraciously; all I saw were snips in evening news and the presentation of the verdict, and documentaries... the DNA evidence went something like this: "this sample show this little marker, which occurs in fraction X of humans ... and it shows that little marker, which occurs in fraction Y ... thus only XY of humans have the combination, and the possibility of there being another person matching this sample is practically nil! You must convict!"
My problem is double: a) how do they know X and Y? When was my DNA sampled, or that of anyone else I know? When were the billion-plus Chinese sampled? (Or are they ignorable for the Simpson trial, which merely begs the question of who isn't ignorable, and were they scientifically sampled?)
And b) how do they know these markers are statistcally independant, that XY is actually their fraction for the population? While I'm willing to grant they may know X and Y well enough, the statistical indepedance (or lack thereof) takes much more analysis to know than than I believe has been done. The prosecution would have to go into serious background to make their "scientific" evidence credulous to me. (And they would have had to handle their case evidence scientifically... a grad student wouldn't get a masters based on labwork of that quality; that anyone's life hung on such bullshit makes a strong argument against capital punishment.)
No... the Simpson jury had ample room for reasonable doubt as far as I can tell, and whining about it is just sour grapes. The prosecution got full of its own importance and deserved to lose the case if that's the best they could do.
I agree that jails are merely almost isolated and very unhealthy social systems that reinforce the very worst behavior in both guards and prisoners. But isolation cannot teach anyone how to alter their behavior; it is used, sparingly, with children because a "time-out" gives them time to reflect rather than react. After childhood is over, the qualities of imagination and openness which make time-outs useful are almost always stunted, particularly in the types of persons who end up (justly or not) in prisons. I certainly would not want prisoners who had been held in complete isolation released into my society again after a "short" term!
We have learned a lot over the hundreds of years we have been locking up criminals, the insane, "delinquent" and "incorrigible" children, and other troublesome types. Unfortunately, we put almost nothing of what we collectively know into solving the problem of violent behavioral deviance. Why? The same reason we don't bother to raise children properly (at least paying attention!); nurse ill persons properly (that is, caring for them, trying to help them rest and sleep so their bodies can heal themselves); or teach properly: It's a lot of work! Hard work... work that requires love. (Love is an active, transitive verb -- seeking the good of the other; it's not some mushy emotion.)
Except in the case of violent offenders, the best technical solution for many crimes is probably an unbreakable monitoring bracelet and frequent supervision, with the offender remaining in touch with family, employment, etc. This is why the modern trend is to release prisoners into half-way houses before their sentence is completely over: They need routines, social contacts, a monitored transition into daily life.
They don't claim that fingerprints are not uniqe, and they don't claim that it's 'no more accurate that handwriting analysis'.
They simply claim that, according to principles of science, it is merely an *assumption* that no two fingerprints are the same. It is not a FACT.
They call into question not whether or not fingerprinting is of use, but whether or not fingerprint evidence should be taken as absolute. They cite the lack of an acknowledgement of an 'error rate', as any scientific method must have.
The point is, courts will jail people for life on fingerprint evidence, yet no modern (or historical) scientific study has *ever* been done to determine how accurate this is. No proper error rate studies have been done. They never take a thousand people and get them to leave prints all over different things, then lift them, and test to see how things work.
and even further off-topic...
Reminds me of the old guy in The Shawshank Redemption. They let him out after many decades of "rehabilitation". He had been so isolated from society, so totally aloof, that he could not bear living in the foreign real world. So he hung himself.
Sometimes it just seems easier to jam our problems in a small dark hole and ignore them instead of actually trying hard to fix them.
It's 10 PM. Do you know if you're un-American?
It was interesting to read in the article that judges have recently had to come up with a better definition of science than "generally accepted" (which would make virgin birth science I guess). One of the requirements they cited was 'falsifiability'. I find this interesting for this reason: falsifiability is crucial for developing science but surely it is redundant in court. Suppose someone wanted to use X in court to prove A is true rather than B. If A is different from B and their argument is sound then this argument itself forms part of a test of the falsifiability of X. If, on the other hand X isn't falsifiable then there is no difference between A and B and so there is no reason why anyone would want to bring X as evidence. So it seems to me that 'falsifiability' is not a useful criterion for deciding whether a 'science' should be used in court (though I'm also saying it's not 'wrong' either). What does anyone else think?
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-- SIGFPE