Murder rate in Iran is half that of the US. Murder in Japan is really low as well, but as discussed in the gun thread, this is because Japan basically has no rights; they are allowed to hold you until you confess.
I suspect that culture has more to do with it than anything else. Japan is a society where following the rules is a huge thing. People don't even jaywalk. They make the Germans and Swiss seems like a bunch of anarchists by comparison. There's also a massive stigma associated with criminality, getting convicted and locked up will get people disowned by their entire families. Never underestimate the power of shame.
