[andrewla]

Sort of. I think the high-order bit here is whether the dog is capable of causing grievous harm. Chihuahuas can be aggressive and can attack without warning, but they will rarely require more than basic first aid to treat, and the possibility of death is practically zero.

At a minimum you are talking about dogs that are capable of killing a child and seriously injuring an adult, and when we talk about the larger breeds in the pit bull family, clearly capable of killing an adult.

Some larger breeds, like golden retrievers, can be ferocious when provoked, and can be dangerous in this regard, but in terms of brute strength are more limited. This is even putting aside differences in temperament.