1. A life sentence can also bring closure to the victim's family. For this to be a valid point, only the victim's family could impose the death penalty
2. A life sentence without possibility of parole will eliminate your concern for parole, I don't think it is reasonable to assume escape as it is very rare.
3. The system does not show more sympathy for the criminal. You might argue that the criminal does, but the only truly valid argument for the death penalty is revenge.
4. DNA testing has not eliminated errors in evidence or errors in prosecution. To me eliminates "almost all uncertainty" is not good enough for me if I am the defendant.
5. Cutting costs is not a good excuse for a bad defense and we would be much more successful in cutting costs and eliminating our overcrowded system if we were to end privatized prisons that are rewarded for keeping people in prison and being much more careful in which crimes are considered serious enough to warrant prison time. It is an absolute disgrace that our "free" country has the highest rate of incarceration in the industrialized world.