Hacker News Reader

Comment by karaterobot | Hacker News Reader

> "We're using tools like crime-gun intelligence, the ability to trace the gun and the spent shell casing from a crime scene to identify who's that shooter, how many violent crimes have they been involved with," she said in the interview.

I don't think that prevents enough crime to account for the drop, though I would believe it helps catch criminals after the fact. I'm basing this on the assumption that the average number of homicide incidents per murderer is somewhere around one, and that most people who are likely to commit murder wouldn't decide to do it or not based on the state of this year's gun-crime intelligence analysis packages.

View on HN

Almost all police activity is there to document crime not to prevent it.

And yes. They’re full of crap here. To the best of my knowledge not once has a recovered shell been matched to the the case casing library system - it was so ineffective that they dropped it after at least a decade of forcing mfgs to supply two shell casings with every handgun made. Shell casings are basically only good for additional evidence, they can’t even be 100% confirmed to the firearm they were shot from. The fact they even mention it is highly suspect in the truthfulness of the claim.

For anyone that believes the stories… she’ll casing almost never have fingerprints on them after being fired. The firing pin indentation is not a scientific match. I can pick up shells and tell you if it was a certain gun, Glocks specifically have blocky firing pins. MP5s have fluted chambers. Extractor marks and ejector dents, etc. But it’s such minor add-on evidence. The reason you might see police marking shells at a crime is for the count of rounds far more than anything else.

> Almost all police activity is there to document crime not to prevent it.

You say this like it's a bad thing (to the extent it's even true). One of the main purposes of the criminal justice system is to deter crime, and in order for the criminal justice system to work, someone has to be supplying the information.

I didn’t imply it was bad at all. Just true. The primary job of police is to document after a crime has been committed. The deterrence doesn’t come from them, but the legal system… notice I said legal system and you said justice system? I think mine is more apt.

Another possible explanation is that some people commit multiple murders and being caught after a successful murder prevents the subsequent ones

> I'm basing this on the assumption that the average number of homicide incidents per murderer is somewhere around one

Let's make up some numbers, say 98% commit a single murder and 2% commit 20 leaving an average of 1.38. If the new system stops every murderer after the first one, the number of murders have a 27.5% reduction. Actual reduction quoted in the article is 12.8%.

So it could very well be true that the average number of murders committed is close to 1 and at the same time the reduction is wholly accounted for by stopping multiple murders.

I still doubt that either cause speculated on in the article are the actual full reason, or even possibly the primary reasons, but it would at least be possible with the information provided.

ithkuil noted that the data may not support that assumption. Merely repeating the assumption is not a very persuasive reply, nor is it a very thoughtful one.

Every serious look into gun forensics I've read indicates that matching a casing or bullet to a specific gun is pseudo-science.

I just wrote about that.

It absolutely is. The worst was when anti-gun groups were pushing “micro-stamping” of firing pins to imprint a number on the primer face. Complete and utter fantasy, easily defeat-able, unenforceable, nonsense. Didn’t stop them from pushing it for at least a decade.

Even the bullet to barrel match of a gun fired in the lab is pretty much BS.

You can tell major aspects like ”the gun this bullet came from had 5R or polygonal rifling” but that is about where it ends in reality. You can prove a bullet didn’t come from some gun, but pretty much never that it did.

Indeed. Not sure where the notion came from that devices mass produced with interchangeable parts would have some kind of mechanical fingerprint that could be forensically identified. Most modern handguns use the browning short recoil action. Of those, most use the Sig Sauer updated system. They are all going to do very similar things cases. That's by design. The most you may ever be able to prove is "yeah this was fired by a glock" Which is next to useless and even then I doubt it.

The factory Glock firing pin is a unique shape. You can tell on those.

What you can’t tell is if someone swapped the firing pin for something rounder.

Apparently the new small frame carry Glocks have round pins (42, 43, 48)

https://hipowersandhandguns.com/Corbon%209mm%20115_files/ima...

Reply on news.ycombinator.com