The death penalty is far to permanent of a punishment to be wielded by organizations with such high false positive rates. We wouldn't put up with it with an anti-virus program or a SMART-esque hardware monitoring program, why do we put up with it when the price is not a few easily replicated digital files or some computer hardware, but rather an innocent persons _life_.
Capital punishment in it's current form is not a deterrence to crime, it doesn't fix the problems caused by the crimes it is punishing for (it doesn't bring back the murdered, etc), it's more expensive for the state (and therefore taxpayers) than life without parole, and innocents have died at the hands of overzealous police, judges, politicians, and public opinion. So the question then becomes, why do it?
We do put up with it in anti virus programs - mcafee deletes Daneware mini remote control service and angryziber ip scan both of which are innocent useful tools.
5 seconds with Google would have given you http://www.deathpenaltyinfo.org/costs-death-penalty which links to multiple sources that have looked into the issue and found that the additional cost of prosecuting the death penalty is significantly more than life without parole. The amount of difference varies with jurisdiction and the methodology of the study, but the differences support the claim.
Unlike many other prosecutors in the state, Jackson ... was personally opposed to capital punishment... He also considered it wasteful: because of the expense of litigation and the appeals process, it costs, on average, $2.3 million to execute a prisoner in Texas - about three times the cost of incarcerating someone for forty years.
Capital punishment in it's current form is not a deterrence to crime, it doesn't fix the problems caused by the crimes it is punishing for (it doesn't bring back the murdered, etc), it's more expensive for the state (and therefore taxpayers) than life without parole, and innocents have died at the hands of overzealous police, judges, politicians, and public opinion. So the question then becomes, why do it?