Another Shooting in the U.S..

one interesting car technology is little microdots that are scattered through luxury cars, so you can trace stolen parts. you can also get custom made DNA. yes it's technically possible to trace guns and even bullets

The technology with regards to firearms is called "microstamping" and generally involves imprinting a mark onto the shell casing by way of the firing pin or chamber interior. California actually passed a law a few years ago requiring that it be implemented by 2010 if practicable. Unsurprisingly, after investigation, the DA admitted that it wasn't practicable for a number of reasons so the law was nullified.

Firstly, it requires that a casing be left at the scene. Easily avoided if shooter uses a shell catcher or revolver. More likely, though, they simply tweak the weapon. Firing pins and barrels are both customer replaceable units. Replacing or defacing the microstamping mark is a piece of cake for anyone who can clean their weapon.

A related system currently in use in two States is aballisticdatabase. Every handgun sold must be fired and a recovered round and casing sent to the State. The theory being that every weapon sold will have an entry on file to make tracing the weapon used easier.

Right. The State of California (which doesn't have aballistic database) believes I own a SIG P2340 in .40 cal S&W. Problem is that by the simple expedient of changing the barrel (which takes less than 60 seconds) I actually keep a SIG P2340 in .357 SIG. Again, barrels on most handguns are customer replaceable units.

Indeed, when California did try looking at a ballistics database, they concluded that it was of limited utility as the failure rate of identifying a match was about 60%. (They testedit on a few hundred police sidearms). Apparently barrels and pins wear out over time. Who knew? (Other than the manufacturers who made the parts easy to replace). Differing manufacturers of ammunution resulting in differing imprints didn't help.

NY and MD have both spent millions of dollars on their databases since 2002. MD has used it to solve one crime, unsure about NY. MD state police_asked that the database be abandoned as a waste of resources.

Which brings us to our last problem. Such expense and effort, even if in the unlikely event that it actually performs as advertised, does nothing to stop a killing. It just makes it easier for the police to find out who did it, which hasn't really been a problem in the high profile shooting so far.

So long story short, nice optimistic idea, won't work.