In Illinois v. Caballes, what are the prerequisites for a K9 sniff on a traffic stop?

The answer is correct because a lawful stop is essential for the legitimacy of a K9 sniff. In the context of a traffic stop, the Fourth Amendment requires that any search or seizure, including a K9 sniff, be conducted within the bounds of the law. If a vehicle is not lawfully stopped, any evidence gathered from a subsequent dog sniff would be deemed inadmissible in court as it would violate the driver’s constitutional rights.

In the decision of Illinois v. Caballes, the court emphasized that the K9 sniff must not extend the duration of the traffic stop beyond its legitimate scope. This reinforces the idea that a lawful basis for the stop sets the foundation for any further actions taken by law enforcement, including K9 sniffs. If the stop is unlawful to begin with, then any subsequent actions are also compromised.