In THEORY, I could support the death penalty in cases like those of Manson, Son of Sam, the Zodiac killer, or Paul Bernardo. Obviously nobody is doing those guys any favors keeping them around until they die of old age in jail cells. The criteria would be:
- Guilt beyond any doubt whatsoever.
- Continuing danger to the public should they ever break out or otherwise get loose.
- Get rid of the present adversarial system of justice and replace it with some sort of inquisitorial system in which the common incentive for all parties was to discover the truth of the matter.
Simply too many ways a death penalty at present could amount to a Mike Nifong having a license to kill people and the basic reality is that in real life, the Bernardos and Mansons are such a small percentage of whatever you're talking about that in real life I could live with letting them rot in prison.
The biggest problem would be finding some sort of an ironclad and foolproof set of criteria for determmmining "guilt beyond any doubt whatsoever". You'd get judges and prosecutors wanting to tell you somebody like Sarah Johnson in Idaho was guilty beyond any and all doubt, while that is simply less than obvious to all observers.
They expected DNA testing to eliminate the prime suspect in felony cases in something like one or two percent of cases and many people were in states of shock when that number came back more like 33 or 35%. That translates into some fabulous number of people sitting around in prisons for stuff they don't know anything at all about since the prime suspect in a felony case usually goes to prison. Moreover, in a state like Texas which executes a hundred people a year or whatever it is, that translates into innocent people being executed on a fairly regular basis.
