""fruit of the poisoned tree". Between their lack of accuracy and a dog's bias towards its handler, they should not ever serve as a basis for search or arrest."

I think this is upside down ... the police are never going to have 'incontrovertible proof' of contraband before they do a full search by definition. If they did need such 'total evidence' to search, they wouldn't need to do the search at all ... they could just make the arrest.

And a dogs hint is not presented as evidence of a crime, merely reasonable suspicion for a search, which is what we want the tool for.

The point is to provide some degree of a reasonable basis for suspicion, after which more effort is used to determine the material outcome: either you have 1Kg of coke, or an illegal gun ... or you don't.

The entire point of the tools are to use something that demarcates reasonable suspicion; dogs, and other things, are viable tools.

If you attempt to enter a country, and you are asked where you are staying but can't provide an answer, or if you do not have a return flight - these are indications of 'reasonable suspicion' of further questioning.