Police dogs are nonsense and send innocents to jail.

And the fault lies not with them, but as usual, with us. Click over for the the in-full detailed article.

The Mind of a Police Dog - Reason Magazine:

"...When we think dogs are using their well-honed noses to sniff out drugs or criminal suspects, they may actually be displaying a more recently evolved trait: an urgent desire to please their masters, coupled with the ability to read their cues.

Several studies and tests have shown that drug-sniffing dogs, scent hounds, and even explosive-detecting dogs are not nearly as accurate as they have been portrayed in court. A recent Chicago Tribune survey of traffic stops by suburban police departments from 2007 to 2009, for example, found that searches turned up contraband in just 44 percent of the cases where police dogs alerted to the presence of narcotics. (An alert is a signal, such as barking or sitting, that dogs are trained to display when they detect the target scent.) In stops involving Hispanic drivers, the dogs' success rate was just 27 percent. The two largest departments the Tribune surveyed—the Chicago Police Department and the Illinois State Police—said they don't even keep track of such information.

...The problem is our confusion about when dogs are picking up a scent and when they are responding to cues from their handlers. The Economist's "Babbage" blog summarizes a recent study led by Lisa Lit, a neurologist (and former dog handler) at the University of California-Davis...

The results? Dog/handler teams correctly completed a search with no alerts in just 21 of the 144 walk-throughs. The other 123 searches produced an astounding 225 alerts, every one of them false.

...the U.S. Supreme Court says a dog sniff is not invasive enough to qualify as a "search" under the Fourth Amendment, so police do not need a warrant or probable cause to have a dog smell your luggage or your car. At the same time, however, the courts treat an alert by a drug-sniffing dog as probable cause for an actual, no-question-about-it search, the kind that involves going through your pockets, opening your luggage, looking in your trunk, and perusing your personal belongings. The problem is that a dog barking or sitting may be responding not to a smell but to his handler's hunch about a suspect's guilt. The reason we have a Fourth Amendment is precisely to prevent searches based on hunches.

The consequences of misusing police dogs go well beyond unconstitutional searches. A drug dog's alert can help establish a connection between a suspect's property and drug activity, allowing police to seize the property for possible forfeiture...

...In 2006 University of North Carolina law professor Richard Myers conducted a statistical analysis 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..."