I don’t believe that I have ever heard this side of the argument against the death penalty. There are state Supreme Court justices that wrote death penalty laws as well as prosecuted murders that resulted in the death penalty who later in life have ruled against the law.
The most notable case is: ‘…As a young state senator 30 years ago, Paul Pfeifer helped write Ohio’s death penalty law. Today, as the senior member of the state Supreme Court, he’s trying to eliminate it….’
And in Florida: “…Gerald Kogan, a retired chief justice of the Florida Supreme Court who prosecuted death penalty cases early in his legal career, now says the death penalty should be abolished, with the possible exception of worst of the worst defendants such as Osama bin Laden or a mass serial killer….”