The extension of a traffic stop to accommodate a canine search is permissible only if:

• A. The dog arrives within a minute
• B. The extension is supported by reasonable suspicion or probable cause
• C. The driver agrees to the extension
• D. The car is towed

Answer: (B)

Extending a traffic stop to allow a canine search must be grounded in Fourth Amendment justification. A stop may be prolonged only to deal with the reason for the detainment, and extending it to bring in a dog is permissible only if there is reasonable suspicion that criminal activity is afoot or probable cause to search exists. When those standards are met, the canine sniff can occur without violating the stop’s limits; without them, lengthening the stop would be unconstitutional. The other options don’t fit because timing of the dog’s arrival, the driver’s consent, or towing the car do not by themselves establish the necessary suspicion or cause to extend the stop.