It's not just the death penalty that needs to change. That's like a chunk of the iceberg that is our criminal justice system. I'm not normally cynical, I love a lot about our country, but our prisons and the volume of our prison system is scary and embarrassing.
I think a lot of these problems can be traced to the existence of private prisons. As long as we have entities that make profit off long sentences and more prisoners, we have a problem.
For-profit prison is just an all-around terrible idea. The whole idea of prison is that it's supposed to provide rehabilitation for criminals that can reintegrate in society, and keep the others from hurting anyone else. A for-profit prison just doesn't fit with that image. Nor does retribution fit with the image of justice.