held to decide whether to extradite Worf to the Klingons in the DS9 episode "Rules of Engagement". In "Doctor Bashir, I Presume?", a JAG rear admiral arranges for Richard Bashir's incarceration—and his son Julian Bashir's retention of a Starfleet commission—as punishment for the illegal genetic enhancements given to Julian as a child. Dialog in "Court Martial" reveals that a court-martial may be convened in the absence of any JAG officers by three presiding command-level officers. Additionally, dialog in "The Measure of a Man" indicates that the loss of a starship automatically leads to a JAG court-martial. Courts-martial were held following the loss of the USS Pegasus and USS Stargazer. In the Voyager episode "Parallax", Tuvok states that the Captain has the authority to conduct a court-martial on the ship, given the circumstance of the ship being isolated from the Federation. Starfleet Medical Starfleet Medical is the medical branch of Starfleet. Gates McFadden, who played Dr. Beverly Crusher, left Star Trek: The Next Generation during its second season. The character is described during this season, and after her return, as having been assigned to Starfleet Medical. Starfleet Operations Numerous star ship dedication plaques identify other personnel associated with Starfleet Operations. Rear Admiral James T. Kirk served 18 months as Starfleet's Chief of Operations. Starfleet Security Starfleet Security is an agency of Starfleet referred to in several episodes of Star Trek: The Next Generation and Star Trek: Deep Space Nine. Security is a branch of Starfleet first introduced in the original Star Trek. Main characters in subsequent series have been security officers. Starfleet Tactical Starfleet Tactical is a rarely mentioned department in Starfleet that is responsible for planning defensive strategies, as well as engaging in weapons research and development. Different species in Starfleet Although Humans are the most-often-seen crew members onscreen, Starfleet is shown to be composed of individuals from over 150 species, with Vulcans perhaps being the most common aliens seen. Already in TOS, the USS Enterprise and other ships have a mixed-species crew, although this does not appear to be an absolute rule; for instance, the episode "The Immunity Syndrome" refers to the USS Intrepid as having an all-Vulcan crew. The Star Trek: Deep Space Nine episode "Take Me Out to the Holosuite" also features such a crew, serving aboard the USS T'Kumbra. In keeping with this idea, Star Trek: Enterprise, in its first two seasons, was the only show