One main reason the death penalty is not a deterrent is that we have sanitized the entire criminal justice process. People used to be flogged, sent to the stocks, and hung in front of the community. These actions reinforced the sense of community and reinforced the harshness of the punishment.
Today, it may take 20 years for someone convicted and sentanced to death to actually die. All that time that the rest of us are footing the bill for their stay in jail.
The death penalty SHOULD be harsh and cruel. These perpetrators do not deserve any sympathy from the rest of us, they are animals who should be put to death inthe most horrrific way possible. It should be televised and held live in public.
IMO, we need to make many changes to our punishment system. A time limit needs to be set for appeals. 3 years after conviction should be the maximum time it takes before sentance is imposed. The trial should be started within 6 months of the arrest. Punishment for crimes of murder, rape, child abuse, and terrorism should be swift and harsh. Additionally, anyone given a sentance that lasts past their life expectancy should also be summarily given the death penalty. Why do we need old folks sitting in prison where they are housed, feed, and provided medical care on my tax dollars? They should be given a choice - pay your own way or die. We do these things and we'll see a reduction in prision costs and a reduction in violent crime.