“Behead” is a shortish word that flows trippingly off the tongue in some Shakespearian soliloquy. I think we need a bit more detail on how that really works if Joe Isis is having a bad hair day. You see, they don’t just cut yer head off, they cut through the wind pipe and muscles and tendons, stopping just short of the spinal column, bend your head back and, with your nervous system still intact, enjoy your rasping, gurgling final attempts of your involuntary nervous system to draw breath. Only when things grow quiet do they complete their severance package and put your head on a pike. There is actually a YouTube video of this.
Maybe the occupation of the future world is to run a knife-sharpening service.