I agree with NM - the death penalty puts you on the same level as them. And technology does not ensure you have the right man (nearly always a man!) any more than the introduction of fingerprinting did. It just improves matters, probably nowhere near as much as is often touted. To say "they can't get it wrong" is simply incorrect - there are all sorts of possible errors such as contamination of or mislabelling of samples, quite apart from the possibility of outright fabrication of evidence. Even if DNA itself is as certain as fingerprints, you still have the question of where the sample came from, for example.
And in any case - are you certain that twenty or more years in gaol is a lesser penalty? As far as the cost goes, the US experience is that capital punishment is not cost effective - it ensures a long drawn out appeal process is carried out even where there is no chance of success, just to postpone the sentence being carried out.
John

