How Reliable Does a Police Sniff Dog Need to Be for a Court to Trust it?

We have all heard of the police sniff dog who jumps into a suspected drug dealer’s car and goes straight for the beef jerky, eagerly eating it up while the embarrassed police handler looks as official as he can.  Or the police dog signals for drugs and nothing is found.  What exactly are the limits or criteria for a police dog’s signal to be sufficient for police to dismantle a car or tear up a house to search for drugs?  Click on the attached link to read a summary of a case that answered this question: http://www.greghillassociates.com/lawyer-attorney-1826928.html