A study of "false positives" involving drug-sniffing police dogs suggests some police forces may be using canines to do an end-run around constitutional protections against search and seizure, and may be profiling racial minorities in the process. A survey of primarily suburban police departments in Illinois, carried out by the Chicago Tribune, found that 56 percent of all police searches triggered by a drug-sniffing dog turned nothing up. But, perhaps tellingly, that number jumped to 73 percent when the search involved a Latino subject -- meaning that nearly three-quarters of all dog alerts on Latinos turned up no contraband.