Owner reports that her 2 y o terrier after having been walked while wearing its harness, bite the husband when he attempted to remove the dog's harness.  

Many dogs, and perhaps in particular, terriers, need to be desensitized to physical handling. When a dog is fearful, reactive, worried, concerned, nervous, anxious about someone fussing about its neck and/or about its body, it will attempt to fight back in the only manner it knows. You see, the dog is attempting to communicate with its squirming.

A desensitization/behavior-modification program has some specific requirements. I believe it's best initially to use a training set-up rather than wait for life to just happen and hope to respond to that.

Question:  If the dog has tasted blood and the purpose was playing with another animal and then "accidently" killing it, can this dog be re-trained and trusted once again?

Over the years and with the help of research into canine behavior, we've been able to learn a lot about dogs and their behavior. But we cannot enter their minds; therefore we cannot understand purpose -- the dog's intent. We may only make som educated guesses.

A woman wrote who was distressed. She had six dogs and many other companion animals. After she'd let the indoors cats outdoors, one was killed by one of her many family dogs.