An officer may stop a car for a traffic violation and then have a drug sniffing dog sniff the outside of the car for drugs. The officer does not need probable cause or even a reasonable suspicion that the car is engaged in dealing in illegal drugs (drug trafficking). For example, if the officer stops a motorist for speeding, the officer may cause a canine sniff for drugs to take place. However, bringing in the dog to sniff around the car cannot extend the length of the stop.
If the officer lacks a reasonable suspicion of drug trafficking and yet delays the traffic stop to wait for the arrival of the drug dog, the detention is illegal. The detention becomes illegal when it continues past the time needed to complete a lawful traffic stop. If drugs are seized in an illegal detention, the person charged with possession of the drugs can request that the drugs not be allowed as evidence at trial.
But what how long of a delay is “too long”. Court cases are all over the place. Just recently, the U.S. Court of Appeals for the Eighth Circuit held in United States v. Rodriguez that seven to eight minutes is de minimis. On the other hand, the Supreme Court of Nevada held a few months ago in State v. Beckman that nine minutes is too long.
If you are faced with a traffic stop that turns into a delay for a canine sniff, the best response is to say nothing, sign nothing and find an experienced criminal defense attorney to handle the matter after the ordeal is over.