He knew even better than she did that you could never predict, any more than you could completely understand, what human beings were capable of. Before an overwhelming temptation everything went down, all the moral and legal sanctions, the privileged education, even religious belief. The act of murder could surprise even the murderer. She had seen, in the faces of men and women, astonishment at what they had done.

The Murder Room, by P.D. James, p. 219