... Wait, is there? This is a fairly common hypothesis for _violence in general_ (it seems to rather neatly explain the big fall in violent crime in most of the

... Wait, is there? This is a fairly common hypothesis for _violence in general_ (it seems to rather neatly explain the big fall in violent crime in most of the developed world in the 90s/noughties, though it's a bit of a just-so story and the timing only really works if you squint at it), but the serial killer thing (in terms of very large numbers of them) seems to be a particularly American phenomenon; if it was heavy-metal linked you'd expect clusters in other heavily industrialised countries.