Not to put too fine a point on it but... the law does not say "citizens shall not kill" it says citizens shall not murder. If someone attacks you and you kill while defending yourself, you have killed but not committed murder. (One attack I have heard made against Republicans in the states is, "How can you be against abortion but for capital punishment." I have never heard the counter argument of how can the Democrats be in favour of abortion but not capital punishment.)
Having said all of that, I am 100% percent against the death penalty. In Canada, in the past ten years, or so, there have been several high-profile cases of people convicted of murder who were later found to be innocent. In one case, the person was repeatedly denied parole because he refused to admit his guilt and he served 23 years before being cleared. At least if the person has been wrongfully convicted it is possible for the wrong to be righted.
