Reply #39: I'm sure that serial number helps a lot in identifying it as a murder weapon

[RaleighNCDUer]

after it was stolen.

With the ballistics on file the slug and the cartridge can identify the weapon. So, your handgun was stolen from your glove compartment when someone broke into your car. That weapon is later identified as the weapon used in a shooting a half-mile away. As a good citizen, you reported the weapon stolen - you are therefore not a suspect. The search for the suspect centers on the area of the shooting, and they know exactly what weapon did the shooting - find the weapon, and they have the shooter.

Of course, if you find your business partner is fucking your wife you COULD report the weapon stolen, then shoot them with it a week later. But that might not work out so well as it did when you could just shoot them and keep the weapon because the police had no record of it.

Every gun crime is committed with a gun that was, once, legitimate. Many are committed by people who never think they will commit one. A ballistics database will catch killers. It's as simple as that.