I can't seem to find it now...
What I found before was an appeal where the decision was made that smell didn't qualfy for probable cause. It had somehting to do with the police force not all receiving training on identifying particular odors.
I did find some other intersting info while I was looking:
A study on why odor shoudn't be used for probable cause
http://www.kluweronline.com/article.asp?PIPS=484203
Ruling in Ontario saying smell isn't reason for search ( I had found something like this for colorado before)
http://www.marijuananews.com/marijuananews/cowan/marijuana_prohibition_in_canada_.htm
Ohio says smell is probable cause
http://norml.org/index.cfm?Group_ID=4202
I will keep looking for that document that I read...i think it was a supreme court appeal. You've got me questioning myself now... However, you'd think that cop would have searched anyway if smell did give him probable cause. He'd already written me up on 3 offences before he mentioned it...he was out to write some tickets that night!
I must say though that I don't think smell should be probable cause. I smoke pot pretty regularly and of course know the smell. Yet, sometimes I'll think i smell weed around me when really it's just a cigarette or clove. I was stopped in Bekeley, CA once for not signalling a turn at 3AM and the cops searched the car becuse they "smelled burnt marijuana". The four of us in the car had nothing on us nor had we smoked that day. There is no way that car smelled like weed, but they were still able to detain us and waste an hour of our time (none of us had committed any offences). Same thing in Utah, we hadn't been smoking, yet he said he smelled weed...just another way to try to get busts by profiling IMO.