What you say is true. But the flaw in your argument is this . . . each dog used in such a capacity (drug sniffer, plant sniffer) only has one handler. While they might be trained by other people prior to being drafted into law enforcement duty, that doesn't meant that their training ends as soon as they are buttigned a human partner.
Where has your car beenMy favorite car of all time was my '84 VW Scirocco, that I paid $900 for. I bought it in Fairfax, VA and it took me to my job in Brentwood...
It is quite plausible to think that a drug dog -might- know certain commands (verbal or nonverbal) that only one human being in the world knows. It's also possible that a drug dog -might- respond to stimulus from the human handler that even the human handler isn't aware of.
For example, the human-dog team is sniffing out drugs for years. During many drug sniffs, the human handler is HOPING the dog will alert so that he can search (insert favorite suspected perp-pain in the butt of the moment). If the dog alerts, the handler responds with more than usual enthusiasm, because he's human and 'happy'. Eventually, the dog learns to spot when the human handler is HOPING that the dog will alert. Maybe his facial expression changes slightly, and the human handler isn't even aware of it. Now you get dogs "alerting" to drugs, because they have learned that it makes their handler happier, at times. That might go a long way to explain how certain "alerts" result in no drugs found. -Dave
