The Naval Criminal Investigation Service (NCIS) was established on December 14, 1993, following the dissolution of its predecessor, the Naval Investigative Service (NIS), due to the fallout from the Tailhook scandal of 1991. This scandal occurred during a reunion of Naval Aviators, known as the Tailhook Symposium, held in Las Vegas, where numerous female civilians and military personnel were sexually harassed and assaulted by officers and enlisted staff.
The investigation into these incidents was mishandled, resulting in severe consequences for some Navy personnel, including ruined careers, early retirements, and letters of censure (administrative action, and the letter is placed in the official service record and is often seen as derogatory material for a promotion or assignment board to consider) that tarnished their official records and impacted future promotions. In response to the scandal, Congress enacted new legislation, leading the Department of Defense to restructure the Investigative Service into an independent organization led by a civilian Director with its ranks made up of an equal mix of civilian and military investigators.