Regarding Christianity and the death penalty, I propose an experiment. Open a public microphone in every church in the US and invite anyone that feels convinced of its truth to state to the rest of the church this one unqualified sentence: “I have committed no sin worthy of death.”
Who would respond? And why?
This is of course aimed more at the churches that have a theology of sin and death; without such an understanding of sin leading to death, the experiment makes little sense. The point is to compel people to an individual, personal evaluation of their relationship to that law of sin and death. Do they believe that they have sinned such that it applies directly to them? Are they now, or were they ever, worthy of death for their own sin?
Only from that perspective can we then pursue a Christian discussion of the death penalty.