Drug-Sniffing Dogs & Probable Cause: Supreme Court Considers When 'A Sniff Is Up To Snuff'

The alert of a drug-sniffing dog might allow police to search your car or baggage, but just how reliable does that hound have to be? The U.S. Supreme Court provided some guidance but rejected a fixed checklist of requirements in Florida v. Harris, the first of two significant dog-sniffing cases that were argued before the high Court last October.

For over forty years, law enforcement officials in the United States have used drug-sniffing dogs as part of their effort to detect illegal narcotics. Police may use such dogs at routine traffic stops or in airports without need for a warrant or probable cause because, as the Court famously ruled in United States v. Place, 462 U.S. 696 (1983), the sniff of a police dog is not considered a search subject to Fourth Amendment protection. Courts have made clear that while the use of a drug-sniffing dog doesn't require probable cause, the dog's detection of the scent of narcotics can produce the probable cause that justifies a police search.

But should that always be the case? In his dissent in Illinois v. Caballes, 543 U.S. 405 (2005) Justice Souter wrote, "The infallible dog ... is a creature of legal fiction." Was Justice Souter right? Are there circumstances under which a positive alert from a drug-sniffing dog does not constitute probable cause for a search? That was the argument from the defendant in the Harris case.

Consider the facts of Harris: a police officer observed Harris's truck on the road with an expired license plate, and pulled Harris over as part of an ordinary traffic stop. After pulling him over, the officer noticed that there was an open alcoholic container in the vehicle and Harris appeared nervous. Harris refused to consent to a vehicle search. Not surprisingly, the officer then retrieved his specially trained police dog, Aldo, from the vehicle and walked Aldo around the truck. Aldo gave an alert at the driver's side door handle that signified he had detected the scent of drugs there. The officer then searched Harris's truck and uncovered ingredients for making methamphetamine. Harris was arrested and released on bail. Amazingly, while on bail, Harris was pulled over again for having a broken tail light by the same officer, and subjected to another sniff and alert by Aldo. The second time, however, the officer found nothing in the truck.

At a subsequent hearing to suppress the evidence found in the first search, Harris argued that Aldo's alert was insufficient probable cause for...