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Pikett is now the target of a class-action lawsuit brought by people who say they were wrongly detained or convicted based on his dogs' alerts. Similar questions have been raised about the methods used by the late John Preston, a former Pennsylvania state trooper who found a second career as a freelance dog handler in police investigations, mainly in Florida. Preston's dog helped convict dozens of Floridians in the 1980s. At least three murder convictions secured through Preston's testimony have since been overturned.
In 2006 University of North Carolina law professor Richard Myers conducted a statistical analysis (PDF) of police dog accuracy tests and concluded that the animals were not reliable enough to produce probable cause for a search, let alone serve as the cornerstone of a conviction. At least five states have banned or restricted the use of scent lineups in criminal cases, but they are still frequently used in courtrooms across the country.
Dogs can be valuable investigative tools. They are great, for example, at following a scent in searches for suspects or sniffing out survivors after a disaster. The bomb-detecting dogs in Iraq and Afghanistan are successful because their handlers have no preconceptions about where bombs may lie. Indeed, they are putting their lives in the dogs' paws. With no cues from their masters to cloud their judgment, the dogs are free to go about their task unbiased. But while Canis domesticus retains many of its wilder relative's sensory abilities, it is in many ways a man-made animal. When we don't take that reality into account, a dog can be worse than useless. But that's not the dog's fault. It's ours.
Radley Balko is a senior editor at Reason magazine.