I don't see any signs of an aggressive dog here. It could be that the lady was afraid of dogs and your lab was just trying to be nice... all the way to the police station. Have you spoken to the police about this? What was the behavior of the dog that leads you to believe you have an aggression problem. If you do have an aggression problem, and want to keep the dog, go find a professional trainer to help you with this issue. Otherwise, keep better control of your dog and don't let him get into a potential troublesome situation like this.