Keyshawn came to live with us in October of 2003. He was given up because of a biting incident related to territorial aggression. He remained in training, in our home, until March of 2005, when I placed him with clients who had recently lost a beloved labrador to cancer.
On my advice, Keyshawn's former owners had taken him through an obedience course, where he learned basic cues at a rapid pace, and even passed a Canine Good Citizen test.
I'm frequently asked whether aggression problems in dogs can be "cured". The answer is most decidedly, yes-- provided the owner is willing to address training, management, social issues, and commit to remaining with new protocols for a long time.
In my experience, it takes 18 to 20 months to modify animals that display social and territorial issues. Once triggers have been identified, prevention of rehearsal of the unwanted behavior must be maintained, while new behavior is conditioned.
In Keyshawn's case, this meant reducing his territory, deranking him through resource in exchange for behavior protocols, and implementing handling exercises that were associated with first meetings with new people, and dogs.