I’m against the death penalty. For one I find it a cruel punishment were the state takes an eye for an eye. Second: it is irreversible. We want to think our justice system is without failure but time and again we have seen that sometimes the innocent are punished for a crime they did not commit just because they were at the wrong place at the wrong time. Last: for the punished it might be an easy way out. Of course dying is very scary, however it happens just once and that was it. From a religious point of view as well as an atheist point of view you could argue that a life sentence is a harder punishment.
If you look at it from an atheists point of view it is an easy way out because death is the end. A murderer with a life long sentence has his entire life to think about what he or she has done, if he or she is able to reflect on his or her actions that is. If they aren’t able to reflect upon their own actions you shouldn’t even think about the death penalty anyway. If the death penalty is sentenced this time to reflect is shortened to just a few years. After the sentence it all stops, there is no soul, no after life and thus is death the easier option as a penalty from an atheists point of view.
Now if you believe in reincarnation you believe that the soul is transferred to a new being after death. If you have been living a good life you will get a better life in the next. If you lived a bad life your will come back in a worse life, maybe not even a human life at all. Now I think we can all agree that a murderer is most likely to come back as some squishy bug or something. This will happen no matter whether we speed up the process or not. So we might as well keep them here before we send them on to be that squishy bug and let them think about why they will be a squishy bug.
Now if you believe in heaven and hell it is a bit trickier to see why we shouldn’t send them on to eternal damnation a little ahead of time. Still it can be reasoned: Eternal damnation is of course eternal and even if we send someone 60 years ahead of time onto eternal damnation it still is only an infinitely small edition to the punishment. If we add years to someone’s sentence here on earth, even if it is just 10 years it is still a large part of a human life time and thus has an actual impact on the punishment.