I agree, you can never be 100% sure, but it is our job as owners that we try never to put our dog in a situation where it is likely to bite. Our old Lab that died at the end of last year, was very trustworthy, he never bit or growled at anyone, he did lots of displays in schools, and scout and brownie groups. He never once gave us reason to think he would bite, did we trust him 100% ?no he was a dog, a very well trained and sociable dog, but still just a dog.