Which in effect means that they are unlimited. They make wide use of drug detecting dogs. If a drug dog indicates you might have contraband, that allows further intervention. It is widely known that drug dogs can , worst case, be trained to hit when a hit is not present. Best case they have a bond with their handlers that tells them that the handler wants there to be a hit, whether the handler consciously conveys that or not. This increases the odds that there will be a hit.
Drug dogs are basically a override-the-law get you into jail free card, and any system that allows them as evidence of probable cause basically does not require probable cause.
