Trip... do you really believe that its impossible for fido to do something completely out of character??
It's not impossible, but it is certainly highly improbable. Dogs are much more predictable and consistent in their behavior than humans by a long shot. They are what they are trained to be. The problem with people who say their dog won't bite however, is that many people haven't trained their dog to not bite, they only think they did. A lot of times people get a dog and they think the only training is housebreaking them. If they are trained and treated inconsistently then they will behave as such. A dog that is trained and given consistent discipline and expectations int he first year or so will pretty much always be consistent. Those patterns are ingrained very early.