"questions left hanging" is not a bad thing for mystery crime novels if you resolve it at some point of the story.
Hmmm. I thought about this, and perhaps not. Maybe the plot is how the lead gets away with it. After all, Steve McQueen does just that in "The Getaway."
You raise an interesting point. Killers never think they're wrong, obviously, and the ones who aren't just sick, demented psychos who enjoy causing pain, or are just high, or it wasn't a crime of passion, do it because they feel they are addressing a percieved wrong that they felt were done on them or someone they loved. They feel like, according to their ego, the world needs them to be a hero by removing the percieved aggressor from existance. Plus, they might even justify it with: "I am protecting myself, my family, and everyone else from this beast!:"
