As a groomer I meet many dogs and have never been afraid of any of them.  Until 3-4 days ago! A lady had asked me to groom her GSD but asked if we could meet off her premises as the GSD was protective of the house.  'OK' I thought.  I met the lady about 1/2 a mile from her house.  The GSD wanted to bite me and if it hadn't been for her owner, I would probably landed up in hospital!
It was clear that the GSD was too protective of her owner and her owner was very concerned as the GSD had gone to bite other people before. Over a short period of time the GSD did get used to me but not enough for me to groom her!  I have suggested that we take her for a walk and build a relationship from there.  More importantly this dog and its owner need help.  The owner can't control her GSD and the GSD is clearly distressed.  As I left the GSD she did try to bite a man walking past her in the street, unfortunately the owner smacked her repeatedly across the nose, not a method I agree with.
Any advice that I can give this owner?  Obviously I have suggested classes etc.

I think the first thing this lady should be thinking about is muzzling the dog when it's outside the home.  The muzzle should, ofcourse, be introduced in a positive way......

Then she needs to think about the message she is sending the dog when she wallops it when ever the dog goes for somebody - the dog isnt' going to make the connection between it's behaviour and the wallop, but simply that when people come close, she's going to get unpredictable - the dog then thinks that keeping people away might be a good idea, and become more defensive.......

Other than that, she really needs to be referred to a behaviourist by the vet, agression like this is not something that can be treated over the 'net - it needs one to one observation of the dog and owner :(

Yes I agree a behaviourist is the way to go...

Totally - tell her to see a behaviourist.  But make sure it's a behaviourist accredited by the APBC, for which she'll need a vet referral.  So tell her to go to the vet with a muzzle and get the dog checked out physically, then get a referral to a behaviourist.