But if my time on the Commission taught me one lesson, it was that I was approaching the question of capital punishment the wrong way. There will always be cases that cry out to me for ultimate punishment. That is not the true issue. The pivotal question instead is whether a system of justice can be constructed that reaches only the rare, right cases, without also occasionally condemning the innocent or the undeserving.
Scott Turow, Ultimate Punishment: A Lawyer's Reflections on Dealing With the Death Penalty (2003).
To put it more baldly, and perhaps less favorably to the status quo (ok, so it wasn't more than enough): Constructing a judicial system that executes exactly the right people, with no mistakes (particularly "false positives"), may well be theoretically possible. But it is not a system in which most judges are elected, prosecutors are either themselves or supervised by elected officials or political appointees, jury duty is seen as something to evade, pretrial publicity—without even considering the First Amendment issues—taints jury pools, peremptory challenges to individual venirepersons are used to shape juries, defense attorneys are ill-funded and obstructed at every turn by the "tough on crime" mentality of law-enforcement officials everywhere, and nobody can agree upon (let alone really knows) the root causes of terminal violence. Although I think the substance of the explanation offered is wrong, Peter Gabriel's chilling portrait of the Kennedy Assassination ("Family Snapshot," from Peter Gabriel [3, "Melt"] should at least give one pause.
I have perhaps been closer to this than most. As a professional manager of violence, I was daily in the position of potentially ordering people to their deaths. Too few of my colleagues ever asked themselves "why?" for me to be entirely comfortable. I do believe that some such orders would/could have been justified; consider, for example, ordering a UXB (unexploded ordnance) specialist in to attempt to disarm a stack of WWII-era bombs discovered next to a school. But it's not an easy question, and that's even with the force of law and special circumstances in the context.