But, having rescued Lamby a year ago, Dunham is doing what she can to rehabilitate him. Rehabilitation doesn't happen overnight -- it takes time and patience to teach a dog not to bite. And just because a dog bites, it doesn't mean the dog is a "bad dog" -- nor does it necessarily mean the owner is a "bad owner." Canine aggression is an incredibly complex behavior, and one incident can't determine how a dog or his owner behaves normally.
Shelter dogs that exhibit aggression are no less deserving of homes -- they may simply need more time and effort, and getting a trainer is the best way to do that. There's no guarantee that a dog can be cured of aggression (and many cannot be cured at all), as the ASPCA writes -- but that doesn't mean that a dog who bites is a lost cause.
Pet parents of aggressive dogs often ask whether they can ever be sure that their dog is "cured." Taking into account the behavior modification techniques that affect aggression, our current understanding is that the incidence and frequency of some types of aggression can be reduced and sometimes eliminated.