Capital punishment in and of itself does not serve as a deterrent to crime.
We in the UK abolished the death penalty in the early '60’s and despite the protestations that society would fall apart the murder rate stayed the same.
What does serve as a deterrent, especially to habitual criminals, is the liklehood of being caught and it is the reason that criminals switch from one offence to another.
On a much lower order of crime is the threatening phone call. Until about three years ago our main telephone provider British Telecom(BT) claimed that it was not possible for the callers number to be made availabe to the called as the system was not capable.
The number of obscene calls soared and when it was revealed that the US had such a system huge pressure was brought to bear on BT which suddenly discovered that their system could provide caller identification.
You will not be surprised to learn that the number of obscene calls has fallen incredibly since the vast majority were from workplaces and domestic residences and the callers could easily be traced.
When speed camers are used the incidence of speeding at that location falls dramatically, all because you will be caught out with absolute certainty.
Wherever cameras are installed in our city centres to monitor street activity crime of all types falls, not just in sight of the cameras, but also in the vicinity since criminals know they will be seen at a particular time and place in relation to the offence.
The building of a national genetic database may well reduce certain types of crime, it is being used to catch offenders who committed their crimes over 20 years ago.
We in the UK are experimenting with the 3 strikes rule but it is not in general use.
When I talk with cons the opinion is almost universal among them that they will be more prepared to kill if it will increase their chances of escape since either way the sentence will be the same, life imprisonment.
This might be true of the relatively few armed criminals we have and some argue that more will carry weapons but I’d doubt it would have much impact on the murder rate since the majority of crime in the UK is non-confrontational.