D. Santiago was a Starfleet officer in the 24th century that served under Admiral Leyton.
In 2372, Santiago was assigned to Engineering Operations. The effective date of this assignment was 49263. This officer was one of over four hundred officers reassigned in a three week period by Leyton. The officer's name was listed in the personnel assignment log that was displayed on a screen in Benjamin Sisko's temporary office in Starfleet Headquarters. (DS9: "Paradise Lost", okudagram)
This character was only mentioned in writing.