I've only read the first 40 posts, so forgive me if this post is redundant or out of sync with the direction of the thread.
I think the premise of this thread is confusing mercy with compassion. I cannot grant mercy on someone unless I have power over them. If someone is starving and I have a sandwich, he is at my mercy. If I give him the sandwich, I am showing him mercy.
If someone has killed a child, I have compassion for the child's family and the killer's family. If someone has accidentally killed a child, I may even have compassion for the grief-stricken perpetrator. I am in no position to show mercy to any of these people, because I have no power over them. A juror may show mercy. A judge may show mercy. A D.A. may show mercy. I cannot. I can only show compassion.
That may be why this thread veered wildly from the get-go. We as a people can show compassion. We are not in a position to show mercy.