“When police officers retrieve a gun at a crime scene, they can trace it to the buyer and consider him as a suspect.”
A complete fiction. This is practically nonexistent as a law enforcement technique. It’s so rare as to be practically unheard of.
And useless because it assumes that crimes are committed by people law abiding enough to purchase and register a gun. Then they go off the rails and commit crimes. Then AT the crime scene, they inexplicably drop the gun, registered to them, and run.
Not correct.
Where I used to live, the local cops would call gun shops with the serial number of the weapon seized or found in order to locate the original purchaser.
Not sure if it ever worked out or not, but I was present for a number of calls in different shops (I knew a few of the cops at the time, and they confirmed it is what they did).