Judge Advocate General's Corps Detachment

All starbases and some major starships have a detachment of the Starfleet Judge-Advocate General's Corps present to advise their commanding officers and shipmates on legal matters, facilitate any necessary legal proceedings, and, if necessary, serve in a prosecutorial capacity in investigations against members of Starfleet. JAG officers wear command division uniforms.

Shipboard JAG Corps Detachment Positions

Staff Judge-Advocate

Lieutenant Areel Shaw, Staff Judge-Advocate at Starbase 11.

Staff Judge-Advocates (SJA) are found aboard the largest starships and starbases of any size. They serve to advise their commanding officer on legal matters, which is critical given how complex interstellar law is, as well as providing legal advice to their shipmates. They prosecute any cases as needed for general courts-martial, while the commanding officer (if they are of sufficient rank) would serve as the judge. SJAs range in rank from Lieutenant Junior Grade (the minimum rank to be qualified as a JAG officer and at which Starfleet Legal Academy graduates start) to Commander, depending on their experience levels. More senior officers are typically assigned to larger commands. A starship would be unlikely to have more than two SJAs, while a starbase might have a dozen or more.

Paralegal Specialist

Paralegal specialists are enlisted members of Starfleet trained in legal research, document preparation, and other ways of assisting JAG officers. They go through substantial training to be able to be as effective as possible. This is a related career track to being a yeoman, and there is cross-over between these two career paths. A starship with a Staff Judge-Advocate would have one to two paralegal specialists, while a starbase with a sector-level JAG office might have several dozen.

Senior JAG Corps Detachment Positions

Command Judge-Advocate

A Command Judge-Advocate serves a similar function to a Staff Judge-Advocate, but for a larger command, such as a Task Force, Division, or Fleet. They are accordingly more senior, ranging from Captain to Rear Admiral. In some cases, they are able to sit as judges, when granted that authority by their commanding officer and the Judge-Advocate General. This is common if the CJA holds flag rank.

Sector Judge-Advocate

Captain Phillipa Louvois, Sector Judge-Advocate for Sector 23 in 2365.

A Sector Judge-Advocate is the senior legal official for a given area of space, generally stationed on that sector's command starbase. They are very senior JAG officers with wide-ranging authority in their area, both advising the flag officer in command of the sector and trying cases at their own discretion, as necessary. While Staff and Command Judge-Advocates do not themselves serve as judges but advise the relevant flag officer to do so, Sector Judge-Advocates have the power sit over courts-martials for lesser offenses and to hold administrative hearings themselves. They report directly to the Judge-Advocate General's Office, and typically hold the rank of Captain to Rear Admiral.

JAG Corps Detachments In-Play

• This is the staff department we've seen the most of on screen, but the specific nature of JAG officers is not fully understood. Some aspects of their work seems consistent with the JAG Corps of the US Military, while other aspects are different. For example, in TOS Commodore Stone serves as the judge along with a panel of command officers to try the case of Captain Kirk, while the JAG officer serves as prosecutor. On TNG, Captain Louvois serves as judge in an administrative hearing to determine whether or not Data is sentient, a decision she seems to have the final say on herself. Ergo, this is written with both of these types of power possible. The JAG officer in TOS would here be a Staff Judge-Advocate (prosecutorial power only) while Captain Louvois was stated to be a Sector Judge-Advocate (prosecutorial and some limited judicial power as well).
• Most ships won't have a JAG Corps Detachment positions, but most stations would.