most searches are random... some people get searched, some dont.. however the dogs are an effective tool for detection of substances.. and those dogs are bloody accurate.. i went to the middle east for a couple of weeks and was smoking hash, at one stage i put the hash in my backpack.. i used the same bag for travelling xcept the hash wasnt in there, but the dog was able to sniff the remaining hash smell that was on the bag... i was asked to empty much bag, nothing was there though...