This handler indicated that he was not sure if the dog was doing the job on the street. Let me assure him, from someone who has been at the dumb-end of the leash that all of us with tracking dogs have had the same feeling. The K-9's on my department have to be able to track very well. They are all trained to track over multiple surfaces and in a wide variety of conditions. I think I can best address this problem by explaining how we train and why we use this method.
Tracking is of course started with very short, highly scented tracks.
We prefer a burlap tug or towel tug. The reason for this type reward system is to allow the dog to fulfill the entire drive that he is using in the tracking. This is very satisfying to the dog and is self-rewarding. I fully believe that tracking is and should be separate from aggression work. If aggression is needed at the end of a track, the dog can very quickly and easily go from a prey mode to an aggressive mode.