Trial courts often uphold searches of cars at traffic stops when the grounds for the search are that a drug dog established probable cause to think that the vehicle was involved in a drug crime. Traditionally, courts have not considered the sniffs to be searches. The United States Supreme Court has relied on two presumptions to uphold searches based on dog sniffs. These are (1) the dog is trained to only signal the presence of the scent of contraband; and (2) the dog does not physically occupy the vehicle but simply walks around the vehicle.
Andrea J. Garland,
Deconstructing Dog Sniffs at Traffic Stops,
106 Marq. L. Rev. 419
Available at: https://scholarship.law.marquette.edu/mulr/vol106/iss2/6