SERIOUS ARGUMENTS Juan non-Volokh links


Juan non-Volokh links to a characteristically over-the-top Dave Kopel essay on ballistic signatures (somehow Kopel convinces himself that keeping a collection of shell casings will lead to requiring DNA samples from all citizens — no, really, here it is) and wants to know “whether there are any serious counterarguments.”

Well, how about these for starters? The crime-solving benefits of the proposed system are substantially greater than Kopel allows, and the primary disadvantage he cites — the creation of a nation gun registry — is a complete fantasy.

We don’t have to speculate about how well ballistic imaging works; it’s being used now on shell casings recovered from crime scenes, and there have been thousands of “hits.” Computer matching is still imperfect, but computer matching is the beginning of the story, not the end; the final step is a physical comparison of two shell casings, with, I am told, negligible false-positive rates. There are ways for clever criminals to get around such a system, but then clever criminals can defeat fingerprinting by wearing rubber gloves. Fortunately, most criminals aren’t that swift.

As to “gun registration,” it is simply not the case that ballistic imaging either implements, or requires, a registration system. Information about the first retail purchaser of any gun must, under current law, be maintained by the dealer who sells it. Given the serial number of a crime-scene gun, it is possible to trace that gun from the manufacturer to the wholesaler to the retailer, and thus to determine who bought it. There is no central database of gun ownership today, and exactly the same thing would be true after the implementation of the proposed system.

Right now, though, there’s no way to trace a shell casing back to the gun that fired it, and therefore to the person who bought that gun. That’s what an imaging system would change. The result would be that a certain number of criminals, and a certain number of the people who illegally supply them with the tools of their trade, would get caught, at modest cost in money (the Maryland system Kopel criticizes is not the proposed national system) and virtually no cost in privacy.

I’m waiting to hear any serious argument for not doing that.


Juan responds, and he and I have been back and forth via email. Apparently what’s freaking out many gun-rights advocates who have no objection in principle to ballistic imaging is the notion, mentioned in several news stories, of a “national data-base.” That has somehow morphed into the idea of a data-base of gun owners.

In fact, what has been proposed is collecting test-fire shell casings, along with the serial numbers of the guns: not the names of the purchasers, which are of course unknown when the manufacturer does the test-firing.

There would be a data-base of images of shell casings, backed up by a physical collection of the casings themselves. A casing found at a crime scene (not quite as common as a bullet, but criminals don’t tend to be very neat) could be checked against that database, and then manually compared with candidate casings to identify the serial number of the gun. That serial number would then lead to the first retail purchase through the gun-buyer forms already maintained in licensed gun dealers’ records. It’s absolutely no different than the current tracing system, except that to start a trace now you need a gun, rather than just a shell casing.

[Three other points, while I’m at it:

1. The national proposal is about shell casings, not bullets. Apparently the technical issues are quite different in the two cases.

2. The Maryland and New York systems are not the proposed national system. There exists a national system of matching crime-scene shell casings, which is working fine, thanks. (For technical and legal reasons, the New York and Maryland data can’t be checked against that national set of crime-scene signatures.) The only question is whether it’s worth adding new guns to the existing national system.

3. As to how easy it is to disguise the ballistic signature of a weapon, and how likely real criminals are to do so, note that the rifle in the truck of Mr. Muhammed has been conclusively matched to the bullets.]


Juan finds the actual proposal, as laid out above, “far less threatening to gun-rights advocates than the proposal Kopel criticized.” I wonder whether the serious gun-rights folks, including Kopel, agree? (Juan, I take it, is about as squishy on gun issues as I am.)

Author: Mark Kleiman

Professor of Public Policy at the NYU Marron Institute for Urban Management and editor of the Journal of Drug Policy Analysis. Teaches about the methods of policy analysis about drug abuse control and crime control policy, working out the implications of two principles: that swift and certain sanctions don't have to be severe to be effective, and that well-designed threats usually don't have to be carried out. Books: Drugs and Drug Policy: What Everyone Needs to Know (with Jonathan Caulkins and Angela Hawken) When Brute Force Fails: How to Have Less Crime and Less Punishment (Princeton, 2009; named one of the "books of the year" by The Economist Against Excess: Drug Policy for Results (Basic, 1993) Marijuana: Costs of Abuse, Costs of Control (Greenwood, 1989) UCLA Homepage Curriculum Vitae Contact: