How Much Police Activity Can Be Justified By Drug-Sniffing Dogs?

Drug-sniffing dogs have been a staple of police work for years, particularly because courts have historically given police broad discretion to use the dogs. But two challenges before the U.S. Supreme Court Wednesday are questioning the limits of dog sniffs, arguing that police have gone too far in allowing drug-sniffing dogs to go anywhere — even to private homes — and to justify anything — even a search of someone’s car.

In one of the two cases before the court, police used the “alert” that a dog gives when it detects drugs as the basis for conducting a warrantless search of a car during a traffic stop. The Supreme Court already held in 2005 that police could use a drug-sniffing dog during a traffic stop without any probable cause. In this case, police seek to take that a step further and allow that sniff alone to justify a subsequent search. Police have typically argued that the risks associated with drug dogs are small, because they are only sniffing for illegal substances, and are not revealing any other private information. But a drug sniff imposes new risks when it justifies a much broader search of a vehicle — particularly when that dog’s findings are not particularly reliable. As Justice David Souter pointed out in his dissent in the 2005 case, the olfactory skills of dogs are not as reliable as they are widely presumed to be:

The infallible dog … is a creature of legal fiction. Although the Supreme Court of Illinois did not get into the sniffing averages of drug dogs, their supposed infallibility is belied by judicial opinions describing well-trained animals sniffing and alerting with less than perfect accuracy, whether owing to errors by their handlers, the limitations of the dogs themselves, or even the pervasive contamination of currency by cocaine. … In practical terms, the evidence is clear that the dog that alerts hundreds of times will be wrong dozens of times.

Souter cites a range of cases showing that the false positive rates for drug dogs can be as high as 60 percent. What’s more, there are no national standards for acceptable success rates nor for what type of training is sufficient, leaving open the possibility that a drug-sniffing dog is sometimes just a cover for widespread searches that could not otherwise be justified by police.


In the second case the justices are considering, the issue is whether any probable cause is needed to justify a dog sniff search at the front door of a person’s private home. Although the dog is not permitted to go inside the home, the defendants argue that the dog sniff is an embarrassing privacy invasion at a particularly sacrosanct location. What’s more, if this type of police activity is justified without any reason for suspicion, what’s to stop police from just walking down streets and through apartment buildings with drug dogs in tow?

Taken together, these two cases demonstrate the magnitude of intervention that can be justified by the presence of drug dogs in the drastically unsuccessful War on Drugs. As a constitutional matter, a practice with such a high error rate should not alone be used to justify searches with no other suspicion requirement. But as a policy matter, what is alarming is that the War on Drugs is still being used to justify increasingly invasive policing.

New FBI statistics show that more people were arrested for drugs in 2011 than for anything else, including a large proportion for mere possession of marijuana. This War on Drugs has played a significant role in earning the United States the title of highest incarceration rate in the world, while exorbitant spending on this so-called war has hardly decreased drug use.