Thats all the head REF has to do - watch what goes on around the QB - now if he doesn't move as the play moves, he may miss something but - when the QBs head does an exorcist turn something is wrong.
There is a problem with the head shots coming from right in front of QB - tough to call either way from the back - that's why there is always someone not happy. Of course, the other refs can chime in too.
These can easily be viewed from the booth.
