Anybody who is still pro death penalty after seeing what's come out of Dallas county in the last decade is probably not worth arguing with.
Capital punishment is one of those things that's great in theory, but impossible to apply in reality. Most will agree that some crimes deserve more than life in prison but the remotest possibility of executing an innocent should terrify any thinking person.
Given the sheer numbers it's almost impossible to believe that it hasn't already happened. This one in particular is as good a candidate as any for a likely innocent death:
http://www.newyorker.com/reporting/2009/09/07/090907fa_fact_grann?yrail
Maybe some good will come of this botched execution. By all accounts he probably wasn't innocent, but the state shouldn't be in the business of executing people anyway and demonstrated incompetence might be good enough to put a stop to it for a while.
Viper GTS <= Former supporter of the death penalty