I do not support the death penalty. In all cases, either death is going too far, or death is too good. Also, while you can let someone out of prison and compensate them for false imprisonment, you can't exactly resurrect people who turn out to be innocent.
In fact, I would say that the whole judicial system could be improved so criminals are rehabilitated, rather than punished.
Of course, I also believe there is an exception to every rule (including this rule), so there's probably an acceptable set of unusual circumstances in which classical imprisonment or even death are the best options; though I do not know what these would be.