Chris, I think you apply a wrong framework to the issue of death penalty. It has little to do with class relations, capitalism etc. although I agree that politicians exploit that issue for electioneering.
As I see, dp has two roots. First is the populist sense of retribution, and-eye-for-an-eye justice if you will, that runs very deeply in popular sentiments. SEcond is that it is a sacrificial ritual that gives people symbolic control over social forces they do not understand. Americans are obsessed with personal security (which is the function of the affluence of the american society), and feel paranoid when that security is threatened. Crime, among other things, threatens that security. However, unlike the "outside threat" can can be symbolically contained by isolationist and nationalist rhetoric, crime is a threat that comes from within - and that is much more scary than, say, the Ruskies coming and "threatening the Amerikan way of life."
In fact, Amerika is a crime-ridden society, much more so than any other developed nation, so that threat is not completely irrational. But your avergae Joe Schmo does not understand that there are deep social and political roots of that crime, among them land use and speculation that uproot communities, economic inequalities, or ant-labour politics to name a few. He feels threatened and he needs some symbolic reasurrance that social order is still intact. Dp is a sacrificial ritual that performs this function, just as human sacrifices were for the Aztecs or Incas.
wojtek