Comment by YZF

I was once in an airport in some third world country and one of those dogs was pointed at my luggage. I was really worried their operator would give them some secret signal to find "drugs" in my luggage. Nothing happened but I can imagine that's a thing.

Those wands were completely fake. Dogs do have a keen sense of smell and can be trained to sniff certain substances.

The polygraph I think is more in the disputed category. It actually measures some physiological signals which in theory could correlate to stress.

That said I don't disagree. These tools can be abused. At the end of the day you need various checks and balances in all these systems (e.g. FBI's internal investigation or whatever body is involved in the security clearances in the US in this example). Applying psychological pressure in various ways is a legitimate tool in these domains.