This character is in charge of all policing inside the Starbase. He/she is responsible for maintaining a safe environment for the crew and maintains and manages the brig. The CSO and his/her department are authorized to use deadly force in any attempt to protect the Starbase from hostile forces within and from without.
The CSO has an office adjacent to the brig but can move about freely. He/she can also appear in the Command Center as mission objectives dictate. This individual works closely with the Marines (CO) for use of forces and who maintain their own brig for military-only situations.
Because of the size of the installation, the Chief of Security position and the Chief Tactical Officer position are two separate posts. However, the Chief of Security often serves as assistant tactical officer and vice versa.
Examples from Star Trek would be Worf, Tuvok, Natasha Yar, Malcom, and Odo.
This is a department leadership position and is heavily featured in almost all missions with many opportunities for activity.