What message type is used for information on individuals already in the system?

The choice that represents the message type used for information on individuals already in the system is Criminal Activity. This type of message can include details regarding ongoing investigations, records related to criminal charges, or any other pertinent data that pertains to individuals who have already been entered into the law enforcement database.

Using Criminal Activity messages allows law enforcement to access vital background information on individuals, including prior offenses, warrants, or other interactions with law enforcement, ensuring they have a complete overview of an individual's criminal history. This is essential for informed decision-making during investigations or when responding to incidents involving these individuals.

The other options do not specifically cater to retrieving information solely about individuals already documented in the system, which is why they don't fit the context of the question as accurately. Broadcast messages, for example, typically disseminate information to a wide audience and do not focus exclusively on individual records. Extradition Verification deals primarily with specifics related to the process of returning individuals to jurisdictions where they are wanted and does not serve as a comprehensive check on criminal histories. Social Announcement messages would generally pertain to community-related notices rather than individual criminal records.