It is pretty easy to tell if a dog is dangerous or not. First, I wouldn't allow my kids to be around a dog that I did not trust. I would no where my child was going and what they were doing so there would be less risk of them being randomly attacked by dogs running loose. I would also teach my child how to deal with violent dogs. There are certain things that need to be looked for when determining if a dog is nice or not. Is its back hair standing up, is the dog puffed up to look big, is it in a stiff position, is it growling, etc. I have encountered many dogs that could have been violent toward me, but because I know how to handle them I don't worry. If people would do a little research on dogs and not get in over their heads no one would have to worry about things like this.