The predictable response: Bring back hanging. The vast majority of people who commit murder or manslaughter, usually with a partner (about 94 per cent) do so under the influence of drink, drugs and/or mental health problems. There has never been a single instance of any country in the world that has cut capital crime by re-imposing death sentences. Drunks, druggies, nutters don't give a monkey's about 'deterrence'. So if you you really want to understand the US, for example, I suggest you look at those states with a death penalty and those that do not. Perhaps, then, you will be able to understand that the death penalty has never been a 'deterrent'.