I'm strongly in favor of the death penalty but it has to have very strong proof of guilt.
A couple of examples of "proof enough" would be Nidal Hassan and the Aurora theater shooter, not much doubt in either of those cases.
As to wrongful convictions. In my perfect world any member of the prosecution ( or defense) from the judge down to the clerk that was involved in any prosecutorial misconduct such as withholding exculpatory evidence, fabrication of evidence, perjury etc... intended to wrongly convict someone of any crime, would upon conviction suffer the same penalty they did or would have imposed on their intended victim up to and including the death penalty. This would also apply to cops either withholding, loosing or fabricating evidence or committing perjury.
Nifong is one example that comes quickly to mind.