Question: why do they use german shepherds as police dogs

title: Police dog
text: Dogs used in law enforcement are trained to either be `` single purpose '' or `` dual purpose '' . Single purpose dogs are used primarily for backup , personal protection , and tracking . Dual purpose dogs , however , are more commonly trained . Dual purpose dogs do everything that single purpose dogs do , and also detect either explosives or narcotics , however , they can not be trained to detect both . Dogs can only be trained for one or the other because the dog can not communicate to the officer if it found explosives or narcotics . When a narcotics dog in the United States indicates to the officer that it found something , the officer has reasonable suspicion to search whatever the dog alerted on ( i.e. bag or vehicle ) without a warrant .