How does DEATH PENALTY deter crime when most criminals dont care for themselves or others?

It has been proven over and over again that the death penalty does not deter crime. It is just a bizarre ritual that we do to make ourselves feel better about ourselves. We sacrifice the blood of some supposed criminal to make ourselves feel better about ourselves as a people. The only problem is that it doesn't work, so we keep doing it in the hope that next time it will work.