I had a similar situation w/a State Patrol Officer in Des Moines. He stopped me for going 3 mph over the (75 mph) speed limit, then double-bound me w/statements such as, "There isn't any reason you wouldn't want me to search your vehicle, is there?" (to which I replied, "Well, aside from the fact that it would delay me, I have a friend awaiting my arrival & have been driving all night, no, not particularly").
I was fairly completely interrogated. I "had" to explain why a friend had recently borrowed my car ("What was wrong w/hers? What kind of car does she own? What year is it? What color is it? How much did it cost to repair it?"), why I was nervous (me: "Aren't most people when pulled over by the police?"), what I do for a living, how was it that a single, unemployed mom of a disabled child had money for a road trip, what were my plans once I reached my destination, how I knew the person I was visiting, how long had I known her, her name, birthday, marital status, etc. It was clear I had no choice but to allow his harassment or he'd have made things MUCH more difficult.
the story: http://tinyurl.com/8x28etd