I am not strongly against the death penalty on principle or on moral grounds- assuming, of course, that it could somehow be narrowly and efficiently restricted to a very few egregiously deserving and certainly guilty criminals.
I don't even find it particularly appalling (or cruel and unusual) punishment that a killer may have some few minutes of physical discomfort before expiring during a clumsily administered execution. My experience as a doctor teaches that dying is never that much fun and I don't see why a heinous criminal should expect a completely free terminal ride when this is not guaranteed to any of the rest of us.
But I do have a very strong objection to the death penalty based purely on practical economic grounds. Killing criminals, whether they deserve it or not, simply costs much more than our society can afford and provides far too little value in return.
Recently, I have appeared as an expert witness in two death penalty cases. Both trials dragged on for many months, produced thousands of pages of documentation, and engaged hundreds of witnesses- including a a platoon of experts arguing for each side.
There seemed to be a limitless budget with no attention to time or money. The stakes are so high in death penalty cases that every procedural nicety must be given its fullest possible due. Judges are extremely concerned about being reversed on a technicality by the appeals courts. This would be embarrassing to them and require a lengthy and expensive retrial. The safest way for a judge to achieve an appeal-proof verdict is always to allow the defense the greatest possible leeway. This encourages defense lawyers to pose every possible objection and to weave every conceivable mitigating theory (however outlandish) hoping that, with enough stuff out there, something may stick with the jury or later with the courts of appeal. The fact that defense lawyers are on the clock (getting hefty hourly fees, usually supported by tax dollars) also provides them with a strong financial incentive to drag things out as long as possible.