Images of Nazi Germany and Soviet bloc checkpoints run through my head. In a free society we should be free from intimidation and being scrutinized for no good reason other than a hunch. Unless there is a dead hooker in the backseat or a large bag of weed/meth laying in the car or a strong smell detectable by the officer, and there is no other evidence of wrong-doing, we should not take the next step.
Cody