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motherFUCKER. I've written a number of times about how forensic science isn't actually science, about how bite-mark analysis, burn pattern analysis, criminal profiling and lie detectors are all examples of pseudoscience, but I thought stuff like rifling pattern analysis would have been "one of the good ones".
However much I hate our knowledge production apparatus, it never seems to be enough.
[EDIT] - ...In fairness, though, the police can say "we caught him with a gun that matches the make and caliber used by the assassin". They just can't say "we caught him with the specific weapon used in the assassination." He's still much better not being in possession of the gun at all.
As someone who has experience in a lab, it drives me up the wall when I hear a prosecution lawyer say the chances of a DNA-related false positive being one in billion; the chance of a lab error or human bad actor being in the chain of custody are both far higher than that. This actually happened a few years ago, a lab manager went to prison for making up test results.
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I always thought matching the gun was about the mark of the firing pin, not the rifling. But it’s not mentioned in the article or the case. Does that still hold up? @NickRiviera, any idea?
I'm sure that if firing pins had a unique identifying pattern on the strike surface, you could probably make something like this work. However I don't think firing pins are really different enough from each other to stake a death-penalty case prosecution on it, I think the best you'd be able to do is rule out suspects as opposed to making a definitive match. However I don't know anything, all I know is that nobody in life seems to be as competent as they want us to believe they are. Seal Team 6 couldn't even attack Osama Bin Laden without crashing their top-secret stealth helicopter, then they couldn't stop Russian/Chinese spies from documenting the crash site before they got it covered with a tarp. If that's the performance you get out of the cream-of-the-crop, then I don't know what to believe anymore. (Not even aliens seem all that competent, crashing their saucers everywhere like a bunch of rookies)
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A case fired from a semi-auto is going to have a firing pin strike, extractor/ejector strikes, and possibly extraction markings on the case wall. The article gives a series of images of firing pin strikes, with the implication being that these are unreliable as well. My guess is that if rifling isn't a reliable "fingerprint", then firing pin and extractor/ejector markings aren't going to be either. If the components are in good condition, they're within a very small tolerance range across all copies of the model, and random variations of impact angle, strength, fouling, etc etc are going to swamp any signal derived from one copy to another.
This should be a stupidly easy thing to test as well. Fire off ten rounds each from ten different handguns. Provide a toolmark analyst all hundred cases, numbered randomly, and have him sort out which ones came from the same gun. My assumption has always been that someone actually did this in the past; if they have, I'd be interested in seeing the data.
Would these handguns be different, but identical examples of the same model (e.g. 10 Glock 19s), or completely different models altogether, united only by chambering? Or both?
I was assuming ten Glock 19s, but it would be interesting to see how far out you could push it. The toolmark analyst claim is that these marks can identify specific weapons, not just a class of weapons.
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