charles severance , 54 , has been charged with murders of nancy dunning , ron kirby and ruthanne lodato , in virginia , over the space of a decade .
prosecution want severance , who was once a fringe candidate for political office , to stand trial for all three killings together .
claims that severance 's ` parable of the knocker ' linked all three deaths .
the three victims were murdered at random in broad daylight when they answered a knock at their front door .