"In this quest for vengeance I think people forget these rules are in place for the State to not abuse it's powers. I'm not against the death penalty because I'm a hippy vegan. I'm against it because I don't think it's a power the state should be able to wield."

I am not sure what the US tries to achieve with the death penalty. Deterrence? Seems not to work. And EU countries have much lower violent crime. Even if they have assault rifles at home (Switzerland). Revenge? An eye for an eye leaves the whole world blind.