Dogs trained to detect the presence of illegal drugs are most likely to provide false alerts in situations involving the search of a motor vehicle, according to the findings of a study published online in the journal Forensic Science International.
A team of researchers from the United States and Poland assessed the ability of trained drug sniffing dogs to accurately detect the presence controlled substances – including marijuana, hashish, amphetamines, cocaine and heroin – in various environments.
Dogs were most likely to correctly identify the presence of contraband, particularly marijuana, during searches of individual rooms. If the dog had previous exposure to the room prior to the search, it was least likely to provide a false alert (83 percent correct identifications versus 10 percent false alerts).
Dogs were far less reliable in scenarios designed to mimic real-world traffic stops. In situations where dogs accessed the perimeter of a motor vehicle, the animals accurately alerted to the presence contraband only 64 percent of the time. Fifteen percent of the time dogs failed to recognize the presence of illicit drugs. Twenty-two percent of the time the dogs indicated that illegal drugs were present when they were not.
Drug dogs’ failure rates were even more pronounced in situations where the animals had access to the inside of a vehicle. In this scenario, dogs correctly responded to the presence of contraband only 58 percent of time. They provided false alerts 36 percent of time.
Previous studies have similarly documented drug dogs’ tendency to provide false alerts. In 2011, researchers at the University of California at Davis reported that the performance of drug-sniffing dogs is significantly influenced by whether or not their handlers believe illicit substances are present. That same year, a review of Australian government statistics, published in the Sydney Morning Herald, found that some 80 percent of drug dog alerts in New South Wales yielded no illicit substances.
In 2005, the United States Supreme Court ruled in Illinois v Caballes that an alert from a police dog during a traffic stop provides a constitutional basis for law enforcement to search the interior of the vehicle.