To help focus: here I only am discussing what happens when you register/license guns (possibly with a bullet/shell casing trace database), with no change in who is permitted to have guns.
Consider what happens when, in the long run, inevitably, corrupt cops, or cybercriminals, disclose part or all of the list:
- When criminals want to steal guns, they know which houses have them
- If instead the criminals want to buy guns (e.g. by “theft” and paying cash), they know to whom to reach out
- If criminals want to rob houses (or people) merely for profit, they know which ones are lower-risk
Moreover, the government has to maintain the registration regime, which takes funds away from e.g. more police officers.
You have to do something with that registration for it to mean something: particularly, you have to prosecute the owners if their guns are stolen, or used in a crime. Otherwise, it becomes trivial for people to suffer “theft” whenever they transfer their guns to organized crime, or just Bubba down the street.
Knowing who originally bought the gun, is a lead in the case; but if you can’t tie the gun back directly to the shooter (notionally, the owner), then the defense attorney easily can claim that the gun was stolen and then used in crime, which is why there is no physical or circumstantial evidence tying the weapon’s recent use to the registered owner. That is: the registration ensures that you include the owner as a suspect in the crime, but the registration does not contribute to the trial. (Even when e.g. the wife is shot in the home, the claim could be that the wife went for the gun and was overpowered.) We also should remember that e.g. all family members, friends, business partners and rivals, local gang members, etc. automatically are suspects in homicide and gun assaults, particularly if leads are few. Hence, the benefit of registration, is when the shooter or ringleader, is not related to the victim; which probably is about 10% of homicides. To realize that benefit:
- The gun can’t be reported stolen, or it can be reported stolen and there has to be a lead in the theft that would point to the new owner
- Either the gun must be recovered, or there must be a bullet/shell casing database
- Investigation of the lead eventually results in the case closure and prosecution
For historical perspective: not only are stolen guns routinely employed by criminals, but the guns repeatedly are sold in the slums, which makes the group of additional suspects quite large. (You could e.g. ban the private sale of guns in order to stop this activity, but then you are not “just” registering guns.) Consequently, we only could consider a significantly discounted number of that 10% of homicides, meaningfully to benefit from the registration lead.
Hence, there is not a theoretically zero benefit from registration alone, but it is difficult to determine in specific cases, whether it would show net benefit vs. spending the money on other crime mitigation approaches.