(noun) police and military slang for a "plant
gun" --
gun placed near or on a suspect by the arresting official as fake evidence of threat.
The term "sock" is used because the plant
gun is usually "found" in the suspect'
s sock, where it is easiest to conceal the act of planting the evidence. In military war zones, it is an illegal but common practice to keep a steady supply of plant guns handy