A special agent or federal agent is an investigator or detective for a governmental or independent agency, who primarily serves in criminal investigatory positions. Additionally, many federal and state special agents operate in "criminal intelligence" based roles as well. Within the U.S. federal law enforcement system, dozens of federal agencies employ federal law enforcement officers, each with different criteria pertaining to the use of the titles Special Agent and Agent.
In general, some agents are federal law enforcement officers and hold either arrest authority or the right to conduct minor criminal/non-criminal investigations. In some agencies, however, a special agent may have both criminal and non-criminal investigatory authority but still have no authority to conduct major criminal investigations.
Regardless, most people holding the title of "Special Agent" are law enforcement officers under state or federal law (with some also being dual intelligence operatives such as with the FBI). These law enforcement officers are distinctly empowered to conduct both major and minor criminal investigations, and hold arrest authority.
Additionally, most special agents are authorized to carry firearms both on and off duty due to their status as law enforcement officers. In U.S. federal law enforcement, the title of "Special Agent" is used almost exclusively for federal and military criminal investigators.
Confusingly, in intelligence usage, "agent" also refers to a human source or human "asset" who is recruited, trained, controlled, and employed to obtain and report information. However, within law enforcement agencies, these types of sources are often referred to as informants, confidential informants (CI—not to be confused with counterintelligence), or confidential human sources (CHS).
Alternatively, some state and local government agencies within the United States title their criminal investigators as special investigators.
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