In my experience cops have been more accommodating.
I had an accident where my car flipped over on a highway*. Among other things, I was transporting some home-brew beers other alcohol. Some were in the trunk, but there were two cases in the backseat. As the car flipped, one of the cases broke open and a couple beers broke and the car reeked of beer.
By the time a cop got there, one of the first things I told the cop was that I was transporting beer and a bottle broke when the car flipped and that's why the car smelled like beer. The cop just said something like "oh, OK." and wrote me up for "driving too fast for conditions". There was nothing in the report about alcohol.
I dunno, maybe the cop was just lazy, but I wasn't tested or anything for alcohol.
* It was last Christmas, I was taking a bunch of beer/wine/liquor back to my family and was driving on a country highway. Light rain, freshly paved road, trunk with lots of weight in it--the car slid out in a turn and I lost control and the car went out and flipped over. I was driving under the speed limit and noone else was involved. Much to my astonishment, I was fine, but confused as to how to remove my seatbelt without falling down onto the roof. But not even bruising or soreness afterwards. I just lost two bottles of beer and a car.