Bullet and Shell Casing Forensics Are a Coin Flip

Quote of the Day

In discussing the Ames II Study, he similarly opined that inconclusive responses should be counted as errors. By not doing so, he contended, the researchers had artificially reduced their error rates and allowed test participants to boost their scores. By his calculation, when accounting for inconclusive answers, the overall error rate of the Ames II Study was 53% for bullet comparisons and 44% for cartridge case comparisons—essentially the same as “flipping a coin.” Regarding the other two phases of the Ames II Study, Dean Faigman found the rates of repeatability and reproducibility “shockingly low.”

Fader, C.J.
June 20, 2023

Good to know if you are ever falsely accused and they are using firearm forensics against you.

Via David Hardy.


17 thoughts on “Bullet and Shell Casing Forensics Are a Coin Flip

  1. What? The courts/government/Hollywood have been lying this whole time?
    I’m shocked! Shocked I tell you!
    And that’s probably a very deep rabbit hole. But what else can we expect from government?
    Government is turning out to be a lot worse than our forefathers told us it was. And I’m pretty sure that the cannibal class invasion being sponsored by same will wipe out whatever reputation it has left for a100 or more years. But I digress.
    Thanks Joe, good info!

    • Milton Friedman said as much 45 years ago. Government grows more powerful, and the private sector seems more trustworthy, so more power and discretion are given to the private sector, until eventually the private sector is seen as corrupt, and power is gradually moved over to the government, and eventually the power corrupts and the government is seen as corrupt, so the “tide” moves the other way.

      • They are all corruptocrats. Big Business looks out for Big Government, and vice versa. No more room in the hot tub for the likes of us.

        There must be a better way.

  2. It comes as no supprise that FBI forensics does not work well. It seems a bit better that the bite mark testing. Lol I understand that with Hammer Fordged barrels the mandrel makes identical barrel rifling over and over. I think the have known this for some time. Just saying.

    • The forensics of how rifling of a pristine slug fired into a water tank is compared to one fired though and into the huge set of variations of densities and shear strengths that exist in the real world is clearly pseudoscience.

      Back when shouting phone books was a thing, the second shot fired into them came out very different because the first shot drastically altered the exact same target.

    • Lots of forensics stuff is less well-founded than “they” usually portray.

      I remember something came out a few years ago—I think it was blood spatter patterns—to be much more unreliable than had been assumed.

      In my opinion there needs to be a thorough vetting and error analysis done on forensics tests, and the results should be presented to juries alongside the test results. So they can analyze for themselves how good the data is that they are trying to sort through. I think it’s only fair. At least they should get error bars.

      It’s hard to quantify “reasonable doubt” — is it a 1% chance? 5%.? 10%? That’s probably up to the jurors. But they should have an accurate idea of how much doubt there is, on both sides.

  3. Fingerprints!
    Have a skin problem the docs call “disshydrolic excema”. Ulcers on fingers and toes, mostly. Turned up in the late 80’s. Which seems to relate to when Aspartame became widely used in food here in the US.
    Turns out, I’m actually allergic to it. Problem is it is found to contaminate a large range of foods. If a manufacturer uses it for any of their food groups, everything else also has it. Consequently, it is difficult to avoid it 100% of the time.
    This allergy became an issue for me when I needed to get fingerprinted for a contractors position with the CHP. Took 18 months of attempts before all my fingers were clear at the same time. The fbi won’t let you mix and match individual fingerprint attempts to get all of them damage free for an application.

    IIRC, most countries ban the use of Aspartame, but Donald Rumsfeld had some sort of financial connection to it, so he was able to get it approved for US foods.

    One would think that if the fbi already had your prints on file, they would accept an application with some visible damage, as long as the good ones match up. Guess again! Every application has to be perfect, as if they have no database to check it against for confirmation. That seems odd, as, supposedly, prints don’t change over time. Might that be something the fbi is hiding?

    So, everywhere you want to get a ccw, the same problem arises, and, you don’t get quick feedback if it isn’t acceptable. fbi is very slow to respond to print applications, which goes back to the state you applied through, and then they contact you, and the whole fiasco starts again…

  4. Even fingerprints are NOT 100% accurate….regardless of the hype about them.
    And don’t even get me started on the BS voodoo nonsense called “forensic odontology”.

  5. How about fiber analysis? Anyone that does one on anything connected with me is going to conclude the dog did it.

  6. There are some high security facilities that don’t count on fingerprints for ID – they use hand shape instead. I’ve been in one and heard about others.
    I’ve read about people breaking a finger and throwing it off badly.

  7. I work with a lot of sandpaper. Trying to open the plastic produce bags in the supermarket is hilarious. I swear people must think I’m retarded.

    I remember a time when the Gun Shot Residue testing done by the FBI was contaminated by the fact that the indoor range air was recirculated throughout the entire building and EVERYTHING tested positive for GSR.

    A lot of things we believe to be a certainty aren’t.

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