The real metric is whether or not firearm-related crimes are significantly reduced in countries where there are prohibitions on firearms.
No, the real metric is whether or not firearms cause a net increase in the amount/severity of crimes - firearm crimes are not the only relevant ones.
There are all sorts of factors which make it a tricky question. Deterrence (burglar is afraid to rob a house, since homeowners might shoot him) is a fairly big effect. Substitution (criminal 1 wants to kill criminal 2, since no guns are around he uses a knife) are some of the biggies. If criminals stab 20 people instead of shooting 15, that's not a good thing.
No, the real metric is whether or not firearms cause a net increase in the amount/severity of crimes - firearm crimes are not the only relevant ones.
There are all sorts of factors which make it a tricky question. Deterrence (burglar is afraid to rob a house, since homeowners might shoot him) is a fairly big effect. Substitution (criminal 1 wants to kill criminal 2, since no guns are around he uses a knife) are some of the biggies. If criminals stab 20 people instead of shooting 15, that's not a good thing.