An android is a robot designed to resemble a human, usually both in appearance and behavior. In the movie "Blade Runner" the action takes place in a futuristic Los Angeles of the early 21 st Century, when the Tyrell Corporation advances Robot evolution into the NEXUS phase – a being virtually identical to a human – known as a Replicant.

The NEXUS 6 Replicants are superior in strength and agility, and at least equal in intelligence, to the genetic engineers who created them. Replicants are used off-world as slave labor, in the hazardous exploration and colonization of other planets.

After a bloody mutiny by a NEXUS 6 combat team in an off-world colony, Replicants are declared illegal on earth – under penalty of death. Special police squads – Blade Runner units – have orders to shoot to kill, upon detection, any trespassing Replicant.

This is not called execution, it is called retirement...