A spaceport police droid (left) and a Guardian police droid (right)
Droids designed for police work were a kind of security droid classified as fourth class. Their programming allowed them to inflict harm on sentient beings, but only under very specific conditions; these conditions were the violation of laws and putting citizens in danger. Their design was specifically for enforcing laws and interacting with civilians, setting them apart from battle droids, which were built for combat and use on the front lines. Although they were immune to both corruption and fatigue, their inflexible, by-the-book thought processes meant they could be outsmarted.
Across the galaxy, various local law enforcement agencies frequently used automated forces to supplement their organic police officers and detectives. However, it was rare for them to completely hand over these responsibilities to police droids. For example, on Coruscant, the local police divisions relied on GU-series Guardian police droids to effectively patrol the vast expanse of the planet-wide city. Furthermore, spaceport police droids found widespread use in spaceports and deep space facilities, where deliberately small organic crews helped to minimize the necessary life support resources.