I'm interested in murder as a phenomenon in various cultures. In Japan we have serious problems recently. Maybe you've heard of them- many murders without motivations. A young man, about 16 or 17 years old, murdered someone without a reason. And when we asked why, he said he wanted to experience the act of murder.
Many murders seem to result from inner motivations rather than life problems.
I don't know if my answer will cover the question in full. I could only say that in my films there never was such a motive and there will never be. I consider this theme forbidden for the art. If there's a work of art, it shouldn't appeal to murder. Especially if it is the art of cinema.