Most people would probably agree that the most engaging stories have interesting characters. And in crime fiction, that can include the murderer. To find the character of the murderer interesting doesn’t mean we condone the killing at the core of the plot. But if the murderer is a layered character who keeps our attention, it’s easier to understand the murder, and it can make for a more absorbing story.

For instance, in Agatha Christie’s Death on the Nile, we are introduced to Linnet Ridgeway Doyle. She seems to have it all: money, intelligence, and beauty. But, on the second night of her honeymoon trip on the Nile, she is murdered. Hercule Poirot is on the same cruise, and he works to find out who is responsible. As it turns out, he develops sympathy for the murderer even though he does not condone what that person did. And as the…