4 ms·

> nobody knows how common it is for someone to have very similar fingerprints to another person Your last example is definitely a good counterexample to this,

> nobody knows how common it is for someone to have very similar fingerprints to another person Your last example is definitely a good counterexample to this, but I feel in most of cases, the suspects are very few so fingerprints only need to be able to distinguish one of the others, than say, identify a random dude from billions. So it's still useable. It's like while SHA-1, or even CRC32, is totally incapable for security, it's still perfectly fine to be used to detect if a known file is corrupted (through natural cause, not deliberately altered) or not.

jrochkind1 4y ago
That's like saying if a witness says "he had brown hair, that's all I can say", and only one of "the suspects" had brown hair, that's reason to convict him.
- Eisenstein 4y ago
  You are misrepresenting the odds of a group of people having an outlier hair color vs a group of people having one which matches sufficiently well to a piece of evidence which excludes the others. 'I remember a brown car' vs "I remember a brown 1976 Ford coupe with worn tires and a broken side window'.
  - pas 4y ago
    please don't forget all the databases that can search for fingerprints, and all the suspects brought before the detectives, and at that point if they did not have a good enough alibi, or good enough psyche to withstand interrogation, or ...
    - dsfyu404ed 4y ago
      https://en.wikipedia.org/wiki/Brandon_Mayfield https://en.wikipedia.org/wiki/Brandon_Mayfield
      - deleted 4y ago
        [deleted]
  - jrochkind1 4y ago
    That's a fair comparison, although I don't know if the numbers work out to a 1976 Ford Coupe or more like a 2005 Honda Civic. But the other thing is, fingerprint analysis is also usually expressed as more like "a 70% chance of being a 2005 Honda Civic with worn tires and a broken side window", the match is always partial (another thing that science doesn't support, those %'s given). But would a jury think someone having a 2005 Honda Civic with worn tires and a broken side window is alone reason to convict someone? Probably not? Would they think "A 75% match with [fingerprint equivalent]" is alone enough reason to convict someone? Usually. Because they are very misinformed about what fingerprint "science" can and does do.
tsimionescu 4y ago
That is not how criminal convictions (is supposed to) work. You don't have to present evidence that proves that, out of these three people, this one is the most likely killer. You have to prove that, beyond any reasonable doubt, this person has definitely committed the crime in question. If there is some reasonable possibility that some unknown person could have come off the street and committed the crime while leaving fingerprints that happen to match one of the suspects, then that suspect should not be convicted.
- mhuffman 4y ago
  >supposed to "supposed to" is doing a lot of work there. People routinely get railroaded in criminal trials because they are too poor to afford good defense or for even sillier reasons like the prosecutor is better looking or more charismatic than the defense attorney.
  - tsimionescu 4y ago
    Absolutely. But making claims like "fingerprints are good for choosing which of the suspects is more likely to have done it" is harming the situation you describe, not helping. That is, it puts even more onus on the defense attorney to explain how the process is even supposed to work.
- rhino369 4y ago
  The totality of the evidence must prove beyond a reasonable doubt. But not every piece of evidence must provide beyond a reasonable doubt. If all you have is a finger print--then yea--the possibility someone else with a close match did creates reasonable doubt. But if the thief was seen in the area at the time and you have a finger print, well that's less reasonable now. TL;DR; apply Bayesian probability.
- thrdbndndn 4y ago
  I'm not saying you should be convicted by a single fingerprint.

jrochkind1 4y ago

That's like saying if a witness says "he had brown hair, that's all I can say", and only one of "the suspects" had brown hair, that's reason to convict him.

Eisenstein 4y ago
You are misrepresenting the odds of a group of people having an outlier hair color vs a group of people having one which matches sufficiently well to a piece of evidence which excludes the others. 'I remember a brown car' vs "I remember a brown 1976 Ford coupe with worn tires and a broken side window'.
- pas 4y ago
  please don't forget all the databases that can search for fingerprints, and all the suspects brought before the detectives, and at that point if they did not have a good enough alibi, or good enough psyche to withstand interrogation, or ...
  - dsfyu404ed 4y ago
    https://en.wikipedia.org/wiki/Brandon_Mayfield https://en.wikipedia.org/wiki/Brandon_Mayfield
    - deleted 4y ago
      [deleted]
- jrochkind1 4y ago
  That's a fair comparison, although I don't know if the numbers work out to a 1976 Ford Coupe or more like a 2005 Honda Civic. But the other thing is, fingerprint analysis is also usually expressed as more like "a 70% chance of being a 2005 Honda Civic with worn tires and a broken side window", the match is always partial (another thing that science doesn't support, those %'s given). But would a jury think someone having a 2005 Honda Civic with worn tires and a broken side window is alone reason to convict someone? Probably not? Would they think "A 75% match with [fingerprint equivalent]" is alone enough reason to convict someone? Usually. Because they are very misinformed about what fingerprint "science" can and does do.

tsimionescu 4y ago

That is not how criminal convictions (is supposed to) work. You don't have to present evidence that proves that, out of these three people, this one is the most likely killer. You have to prove that, beyond any reasonable doubt, this person has definitely committed the crime in question. If there is some reasonable possibility that some unknown person could have come off the street and committed the crime while leaving fingerprints that happen to match one of the suspects, then that suspect should not be convicted.

mhuffman 4y ago
>supposed to "supposed to" is doing a lot of work there. People routinely get railroaded in criminal trials because they are too poor to afford good defense or for even sillier reasons like the prosecutor is better looking or more charismatic than the defense attorney.
- tsimionescu 4y ago
  Absolutely. But making claims like "fingerprints are good for choosing which of the suspects is more likely to have done it" is harming the situation you describe, not helping. That is, it puts even more onus on the defense attorney to explain how the process is even supposed to work.
rhino369 4y ago
The totality of the evidence must prove beyond a reasonable doubt. But not every piece of evidence must provide beyond a reasonable doubt. If all you have is a finger print--then yea--the possibility someone else with a close match did creates reasonable doubt. But if the thief was seen in the area at the time and you have a finger print, well that's less reasonable now. TL;DR; apply Bayesian probability.
thrdbndndn 4y ago
I'm not saying you should be convicted by a single fingerprint.