The point is, if the option for the juror exists to incarcerate without putting someone else (such as a corrections official or other inmate) in undue mortal danger, it is better to give the offender the most possible time to repent of their crime. It is not just that we may not play God, but also that we must hope for the most chances for the soul of the murderer to escape eternal punishment. For us, that means not shortening someone’s life artificially when protection of another life from their aggression doesn’t require us to do so. Still, I think it has to be allowed that some offenders could be fairly seen as ticking time bombs. If it is only a matter of time before they murder again, it is an act of defense of their victims to give them the death penalty. I’d think that a fairly rare case in the US, although I’d listen if a prosecutor made it.