By: John Burnett

Dogs have an incredible sense of smell. In fact, a dog’s nose is so much more sensitive than a human’s that, analogized to vision, “what you and I can see at a third of a mile, a dog could see more than 3,000 miles away and still see as well”[1]. In addition to scientific evidence of canine smelling superiority, there are the countless representations of crime-fighting pooches using their noses to find the drugs and bust the bad guys. Despite this common depiction however, the application of drug-sniffing dogs in American law enforcement is surprisingly flawed and open to error. As science suggests, the flaw is not with the dogs’ ability to detect smells, but rather with training and their law-enforcement handlers. These defects have been made known to courts and yet despite perverse incentives, the practice has gone uncurbed. Even when “no better than a coin flip,”[2] the use of drug-sniffing dogs to establish probable cause sufficient for searches and seizures has been given strong approval by circuit courts and the Supreme Court[3].

While dogs naturally possess amazing olfactory capabilities, they have been bred for generations to serve a higher purpose: make their human happy. As such, dogs have developed the highly perceptive ability to read human body language and respond accordingly. This combination creates the problem that the more a handler wants drugs to be found, the more often a dog is to alert. In one case[4] a police handler’s dog alerted 93% of the time, with a success rate of only 59%, but the dog received a treat every time it alerted no matter the result. This reward system undermined the dog’s training and encouraged it to alert to receive a treat whether there were drugs detected or not. The Supreme Court critiqued this kind of behavior, but ultimately deferred to the handler’s testimony of accuracy in the field[5]. Controlled studies have confirmed these biases as tests designed to fool handlers are far more likely to trigger false alerts than tests designed to fool dogs[6]. Additionally, drug-sniffing dogs tend to be less accurate than their bomb-sniffing counterparts since the latter’s handlers have an incredibly strong incentive to be right[7].

The urge to please a handler can also be seen from instances in which dogs, miraculously, alert on contraband they’re not trained to detect like fake passports[8] or untaxed cigarettes[9]. As the Washington Post pointed out,“[e]ven the smartest of police dogs can’t determine with a sniff whether a trunk-load of Marlboros was purchased in or out-of-state. (Not to mention that the dog wasn’t trained to detect tobacco.) The dog likely was merely reflecting whatever suspicions its handler had about the driver.” The Chicago Tribune found in a local study that when a police dog alerted to the presence of drugs during traffic stops that drugs were discovered just 44% of the time[10]. Additionally, the article found that in stops involving Hispanic drivers, the dogs’ success rate dropped to 27%[11]. Again, the evidence indicates a breakdown in training in which dogs are urged, consciously or not, to alert when their handler finds someone suspicious regardless of guilt.

Despite exhaustive empirical evidence[12] showing the susceptibility of drug-sniffing dogs to become biased and inaccurate by the desires of their handler, courts have generally refused to question the propriety of arrests made based on dog-generated probable cause. So long as the dog is certified, or has received recent training, the Supreme Court has found[13] that wildly inconsistent success rates in the field will not diminish the propriety of a search even if the suspect is found to have illicit materials different than those that the dog is trained to detect.

Unreliable drug-sniffing dog alerts have been upheld by various courts around the country with field success rates of 59.5%[14], 57%[15], and 43%[16] being found sufficient with little ambivalence. The Supreme Court has rejected the idea that field tests should be the “gold standard,[17]” and in fact wrote that a dog’s field record is of “relatively limited import.[18]” Given these rulings, it is difficult to legally impugn the reliance of police officers on “certified” drug-sniffing dogs to detect contraband.

Despite the fact that there are little to no legislative regulations or standards for drug-sniffing certification, the Court wrote in Florida v. Harris that the police’s interest in having useful (that is “accurate”) dogs would prevent sloppy certification. However, as many have pointed out, poorly trained (excessively alerting) dogs “waste” police officer’s time, but provide easy probable cause to search a suspect’s property. The combination of easily obtained probable cause and lax forfeiture laws in some states, provide a clear and contemptible incentive for police to have poorly trained dogs.

When used properly, drug-sniffing dogs can be essential and relatively unobtrusive tools for confirming or clearing someone of suspicion. But when police are given carte blanche, an environment is created in which officers are encouraged to use poorly trained dogs to subject innocent citizens to unreasonable searches based on no more than a hunch. These practices, especially if left unchecked, allow for the kinds of arbitrary searches and seizures that the 4th Amendment is designed to preclude.

[1] Peter Tyson, Dog’s Dazzling Sense of Smell, NOVA scienceNOW (Oct. 12, 2012),

[2] Radley Balko, Federal appeals court: Drug dog that’s barely more accurate than a coin flip is good enough, Washington Post (Aug. 4, 2015),

[3] Id.

[4] United States v. Bentley, 795 F.3d 630, 636 (7th Cir. 2015).

[5] Radley Balko, Federal appeals court: Drug dog that’s barely more accurate than a coin flip is good enough, Washington Post (Aug. 4, 2015),

[6] Id.

[7] Id.

[8] Radley Balko, Supreme Court Considers Two Drug Dog Cases, The Huffington Post (Jan. 23, 2014),

[9] Id.

[10] Id.

[11] Id.

[12] Id.

[13] Florida v. Harris, 133 S. Ct. 1050, 1056 (2013).

[14] United States v. Bentley, 795 F.3d 630, 636 (7th Cir. 2015).

[15] United States v. Holleman, 743 F.3d 1152, 1157 (8th Cir.).

[16] United States v. Green, 740 F.3d 275, 283 (4th Cir. 2014).

[17] Florida v. Harris, 133 S. Ct. 1050, 1056 (2013).

[18] Id.