From the CBSA perspective, detector dogs can also hit and be...infallible. Usually, though, from our experience, when you couple the ion scan, the detector dog, and the X-ray, we've had a very good success rate, trying to find these concealed goods, whatever they might be. Usually the officer, through questioning, can explain why the detector dog or the ion scan might have identified something that isn't there. If it was a false positive or a nuisance alarm, the person might have just used narcotics prior to getting on the plane or prior to getting out of their car. That would explain why the dog did hit or identify a positive.
On March 20th, 2018. See this statement in context.