Troy Davis was executed today. Professor Quirrell explains why pretty well:

“Welcome, Mr. Potter, to your first encounter with the realities of politics. What do the wretched creatures [on death row] have to offer any [politician]? Who would benefit from aiding them? A politician who openly sided with them would associate themselves with criminals, with weakness, with distasteful things that people would rather not think about. Alternatively, the politician could demonstrate their might and cruelty by calling for [more executions]; to make a display of strength requires a victim to crush beneath you, after all. And the populace applauds, for it is their instinct to back the winner.” A coldly amused laugh. “You see, Mr. Potter, no one ever quite believes that they will go to [death row], so they see no harm in it for themselves. As for what they inflict on others… I suppose you were once told that people care about that sort of thing? It is a lie, Mr. Potter, people don’t care in the slightest, and if you had not led a vastly sheltered childhood you would have noticed that long ago.

Unlike a recent Texan execution, he wasn’t almost certainly innocent, but the Supreme Court’s argument is more disturbing: that since he’d been proven guilty beyond reasonable doubt at his appeal, he’d have to be proven innocent beyond reasonable doubt to be freed. In particular, there’s no prohibition specifically against executing someone who’s probably innocent, as long as at some point a jury had ruled that the chance he was innocent was less than 5%.