Drug sniffing dogs are wrong 80% of the time, according to new statistics from Sydney, Australia.
In response to an inquiry from the Australian parliament, Sydney police provided statistics showing that in 80% of the cases where dogs have indicated positive for drugs, no drugs were found after a search. http://www.smh.com.au/environment/animals/sniffer-dogs-get-it-wrong-four-out-of-five-times-20111211-1oprv.html#ixzz1gRA1enLH
U.S. police departments also rely heavily on drug sniffing dogs to establish probable cause to search, but statistics on reliability are not typically released.
Drug sniffing dogs must be certified under controlled conditions, but how they actually perform in the field is a mystery. Most people who are searched with negative results usually move on without reporting the encounter, so real life stats are not available. But these results from Australia indicate that the reliability of drug sniffing dogs is poor.