(Consider this brief rant a barely-pre-meditated random outburst, so it's not very long or very fancy, but it still needed saying.)
A: "Woaw, why did you tie that guy to a tree!?"
B: "I have reason to believe that he murdered someone!"
A: "Wow, really? That's serious! What's your proof?"
B: "My pet parrot said 'murderer' while this guy was nearby!"
A: "What? How does your parrot even know how to say that?"
B: "I trained him to say it."
A: "So your pet did something you trained it to do? And you're using that as supposed proof that someone did something bad? To the point that you'd violently detain him??"
B: "Absolutely!"
A: "Is your parrot ever wrong?"
B: "All the time. Mostly he's just responding to my signals. I can make him say 'murderer' whenever I want, regardless of who is around."
A: "It sort of seems like the entire purpose of the parrot is to give you a lame excuse to be a violent asshole!"
B: "Shut up! You must just be a nasty criminal!"
And that, ladies and gentlemen, is the reality of cops and their "drug-sniffing dogs." The dogs get it "wrong" a huge percentage of the time, but it is not because the dogs are defective; it's because the goddamn police train them to "signal positive" on command--regardless of any scent of drugs--and the stupid American people accept that as "probable cause" justifying fascist detainment, theft, searches, destruction of property, etc. "Well gee, that trained dog sniffed a thing, so I'm all in favor of treating that random person like an evil criminal!" Good grief, people. How gullible can you be?
(P.S. For confirmation: http://thefreethoughtproject.com/court-case-reveals-police-dogs-signal-drugs/ )