A police dog, known as a "K-9" or "K9" (a homophone of "canine") in some English-speaking countries, is a dog that is specifically trained to assist police and other law-enforcement personnel in their work. Their duties include searching for drugs and explosives, searching for lost people, looking for crime scene evidence, and protecting their handlers. Police dogs must remember several hand and verbal commands. The most commonly used breed is the German Shepherd.