Two parts "Lock, Stock, & Two Smoking Barrels." One part "Pulp Fiction." Mix well. The similarities are almost too strange to be true: armed robbery of a man growing marijuana at home, and a samurai sword saving the day. Of course, the prison sentence of eight years for manslaughter never appeared in either movie, but that's a minor detal. Found this story on Tactitus.
I think the most important fact in this case is that all of the wounds were from behind. It is not really self-defense if you stab a man in the back.