4 ms·

The whole field of forensics is looking a lot like junk science. I remember when fingerprints were exposed as bogus. Now it seems every other type of forensics

by zik 3y ago

The whole field of forensics is looking a lot like junk science. I remember when fingerprints were exposed as bogus. Now it seems every other type of forensics turns out to be faulty when it has the slightest scrutiny. Even forensic DNA testing while potentially good science has ridiculous claims made about it - "one in a billion chance of being wrong". But it turns out they wrongly convict people using "unimpeachable" DNA evidence fairly often [1]. [1] https://www.science.org/content/article/forensics-gone-wrong-when-dna-snares-innocent https://www.science.org/content/article/forensics-gone-wrong...

drewcoo 3y ago
"Justice" isn't based on factual science, though. It's based on precedent.
rendall 3y ago
Fingerprints were exposed as bogus?
- deleted 3y ago
  [deleted]
- Spivak 3y ago
  They don't stand up to the claims that prosecutors make about them and get treated as far far more reliable evidence than they actually are. There is some signal in there but analysis of only a few prints or partial prints should be treated as extremely suspect if that's all you got. The place where the limited data is at its strongest is when you know there were only say 3 people who could have made that print because you can reliably rule the others out if they physically couldn't have made the print you lifted. But if you're going fishing and all you have is some prints matched against a database the idea of a "match" meaning anything other than "is part of a cohort of unknown size that could have made that print" should be thrown out.
- Etheryte 3y ago
  Quoting from [0], but there are many other sources with similar stats: > One study of FBI fingerprint analysis found that false-positive errors in which a fingerprint was incorrectly matched with a suspect occurred in one out of every 306 cases. A study of a Florida police crime lab was even more troubling, finding that false-positive errors occurred in one out of 18 cases. [0] https://www.connecticutcriminallawyer.com/personal-injury-attorney-blog/how-reliable-is-fingerprint-evidence-in-criminal-cases https://www.connecticutcriminallawyer.com/personal-injury-at...
  - kspacewalk2 3y ago
    That is certainly very far from bogus, unless you use bogus language like "it's a match". If instead you reasonably estimate the probability of error, updating your prior by a test with 1/18 error rate is very valuable.
    - zik 3y ago
      A one in eighteen chance of error isn't really good enough to convict someone on in the absence of other evidence. [1] https://www.smithsonianmag.com/science-nature/myth-fingerprints-180971640/ https://www.smithsonianmag.com/science-nature/myth-fingerpri... [2] https://www.sciencedaily.com/releases/2024/01/240110120225.htm https://www.sciencedaily.com/releases/2024/01/240110120225.h...
      - Tagbert 3y ago
        and that would be the point. Any single piece of evidence, particularly something with a noticable error rate, should not be enough to convict someone. It might be enough to investigate someone, but there should be corroborating evidence.
    - resoluteteeth 3y ago
      When people say "fingerprints are bogus" they aren't saying that fingerprints literally don't exist, they are saying that the claims law enforcement/forensics people have made about their usefulness in uniquely identifying people are bogus. If there is enough error to discredit those claims, it's reasonable to say that the claims are bogus even if fingerprints do still have some value in identifying people.
- foxyv 3y ago
  There is some controversy because they are definitely fallible. Much more fallible than was believed before 2005. https://www.bu.edu/sjmag/scimag2005/opinion/fingerprints.htm https://www.bu.edu/sjmag/scimag2005/opinion/fingerprints.htm
ajb 3y ago
There's a general principal involved, that once you start throwing round numbers like 'one in a million' around, you're almost certainly overlooking larger sources of error. Eg, someone fucking up in the lab is much more likely than one in a million. There was a famous case where they were looking for (what they thought was) a serial killer who showed up in a bunch of DNA tests, and it turned out to be some factory worker who had contaminated the swabs.
- jerf 3y ago
  I think of it as the "noise floor" of probability. It's great that, say, the odds of a DNA match is one in a trillion, but the odds of someone getting there wrong sample, misreading the results, deliberately forging the results, etc. is so much higher that the probability really only tops out (or bottoms out, depending on your perspective) at the noise floor. Comes up a lot in our world because computers so easily generate those large probabilities by being the things that can run millions of "samples" of some distribution per second, but you always have to cap those analyses to the probability noise floor or you'll be very misled.
  - alexpetralia 3y ago
    This is basically Bayes rule: the probability we have an accurate test given perfect conditions. But what is the baseline rate of perfect conditions? If it's less than 1, then our "posterior" probability will not be one in a trillion anymore, but something far less.
- ArnoVW 3y ago
  If memory serves, the police were using swabs that was marked sterile but not rated "for use in forensics"
  - ajb 3y ago
    Yes, you are correct. The case is this one: https://en.wikipedia.org/wiki/Phantom_of_Heilbronn https://en.wikipedia.org/wiki/Phantom_of_Heilbronn
KennyBlanken 3y ago
[flagged]
- dang 3y ago
  We've had to warn you many times about breaking the site guidelines. There's no reason you couldn't have made your substantive point here without obvious flamebait like "feminists shriek". Moreover you've been continuing to break the rules in other places too: https://news.ycombinator.com/item?id=39031585 https://news.ycombinator.com/item?id=39031585 https://news.ycombinator.com/item?id=38988354 https://news.ycombinator.com/item?id=38988354 I appreciate your positive contributions to HN, but if you keep this up we're going to end up having to ban you. I don't want to do that, so if you'd please review https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html and properly fix this, that would be good.
- Capricorn2481 3y ago
  > The reason most of them are untested are various reasons like: the perp was conclusively identified otherwise or confessed Source? Why would anyone be upset about untested rape kits if rapists were being caught like you claim
- deleted 3y ago
  [deleted]

by zik 3y ago

drewcoo 3y ago

"Justice" isn't based on factual science, though. It's based on precedent.

rendall 3y ago

Fingerprints were exposed as bogus?

deleted 3y ago
[deleted]
Spivak 3y ago
They don't stand up to the claims that prosecutors make about them and get treated as far far more reliable evidence than they actually are. There is some signal in there but analysis of only a few prints or partial prints should be treated as extremely suspect if that's all you got. The place where the limited data is at its strongest is when you know there were only say 3 people who could have made that print because you can reliably rule the others out if they physically couldn't have made the print you lifted. But if you're going fishing and all you have is some prints matched against a database the idea of a "match" meaning anything other than "is part of a cohort of unknown size that could have made that print" should be thrown out.
Etheryte 3y ago
Quoting from [0], but there are many other sources with similar stats: > One study of FBI fingerprint analysis found that false-positive errors in which a fingerprint was incorrectly matched with a suspect occurred in one out of every 306 cases. A study of a Florida police crime lab was even more troubling, finding that false-positive errors occurred in one out of 18 cases. [0] https://www.connecticutcriminallawyer.com/personal-injury-attorney-blog/how-reliable-is-fingerprint-evidence-in-criminal-cases https://www.connecticutcriminallawyer.com/personal-injury-at...
- kspacewalk2 3y ago
  That is certainly very far from bogus, unless you use bogus language like "it's a match". If instead you reasonably estimate the probability of error, updating your prior by a test with 1/18 error rate is very valuable.
  - zik 3y ago
    A one in eighteen chance of error isn't really good enough to convict someone on in the absence of other evidence. [1] https://www.smithsonianmag.com/science-nature/myth-fingerprints-180971640/ https://www.smithsonianmag.com/science-nature/myth-fingerpri... [2] https://www.sciencedaily.com/releases/2024/01/240110120225.htm https://www.sciencedaily.com/releases/2024/01/240110120225.h...
    - Tagbert 3y ago
      and that would be the point. Any single piece of evidence, particularly something with a noticable error rate, should not be enough to convict someone. It might be enough to investigate someone, but there should be corroborating evidence.
  - resoluteteeth 3y ago
    When people say "fingerprints are bogus" they aren't saying that fingerprints literally don't exist, they are saying that the claims law enforcement/forensics people have made about their usefulness in uniquely identifying people are bogus. If there is enough error to discredit those claims, it's reasonable to say that the claims are bogus even if fingerprints do still have some value in identifying people.
foxyv 3y ago
There is some controversy because they are definitely fallible. Much more fallible than was believed before 2005. https://www.bu.edu/sjmag/scimag2005/opinion/fingerprints.htm https://www.bu.edu/sjmag/scimag2005/opinion/fingerprints.htm

ajb 3y ago

There's a general principal involved, that once you start throwing round numbers like 'one in a million' around, you're almost certainly overlooking larger sources of error. Eg, someone fucking up in the lab is much more likely than one in a million. There was a famous case where they were looking for (what they thought was) a serial killer who showed up in a bunch of DNA tests, and it turned out to be some factory worker who had contaminated the swabs.

jerf 3y ago
I think of it as the "noise floor" of probability. It's great that, say, the odds of a DNA match is one in a trillion, but the odds of someone getting there wrong sample, misreading the results, deliberately forging the results, etc. is so much higher that the probability really only tops out (or bottoms out, depending on your perspective) at the noise floor. Comes up a lot in our world because computers so easily generate those large probabilities by being the things that can run millions of "samples" of some distribution per second, but you always have to cap those analyses to the probability noise floor or you'll be very misled.
- alexpetralia 3y ago
  This is basically Bayes rule: the probability we have an accurate test given perfect conditions. But what is the baseline rate of perfect conditions? If it's less than 1, then our "posterior" probability will not be one in a trillion anymore, but something far less.
ArnoVW 3y ago
If memory serves, the police were using swabs that was marked sterile but not rated "for use in forensics"
- ajb 3y ago
  Yes, you are correct. The case is this one: https://en.wikipedia.org/wiki/Phantom_of_Heilbronn https://en.wikipedia.org/wiki/Phantom_of_Heilbronn

KennyBlanken 3y ago

[flagged]

dang 3y ago
We've had to warn you many times about breaking the site guidelines. There's no reason you couldn't have made your substantive point here without obvious flamebait like "feminists shriek". Moreover you've been continuing to break the rules in other places too: https://news.ycombinator.com/item?id=39031585 https://news.ycombinator.com/item?id=39031585 https://news.ycombinator.com/item?id=38988354 https://news.ycombinator.com/item?id=38988354 I appreciate your positive contributions to HN, but if you keep this up we're going to end up having to ban you. I don't want to do that, so if you'd please review https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html and properly fix this, that would be good.
Capricorn2481 3y ago
> The reason most of them are untested are various reasons like: the perp was conclusively identified otherwise or confessed Source? Why would anyone be upset about untested rape kits if rapists were being caught like you claim
deleted 3y ago
[deleted]