One evening a couple of weeks ago, I passed a murderer in the front square of Trinity College Dublin. He didn’t look like a murderer – or he didn’t look like whatever it is murderers are supposed to look like. With his wavy white hair swept back from his high forehead, his tweed jacket, his beige slacks and blue oxford shirt, he could easily have passed for a professor nearing retirement age, scuttling between lectures while trying to avoid running into his students. He was even carrying an A4-sized folder under one arm. At first I thought he was someone I vaguely knew, and was about to nod blandly in his direction, when I realized why it was that I had recognized him. I must have done a quite blatant double take, because as we passed each other beneath the campanile he shot me a sidelong look of almost cartoonish wariness and culpability – swiveling his eyes toward me, and then away, and then quickly back again. He looked frightened.