Visible crew/equipment: In one of the first episodes (2nd or 3rd) of Season 1, in an interrogation room scene, the camera pans around the table, and a crew member is visible in the far wall mirror, standing beside the camera in front of Gibbs.
Factual error: While the NCIS crew are working a crime scene, Ducky starts yet another parable about his past experiences, referring to the dating of an Indian skeleton by the caliber of the bullet, "a 40-75". He states that since he knew the year that the US Army used that caliber, he could accurately date the remains. Unfortunately for Ducky, the US Army never used a 40-75. It did, however authorize a contract for a 45-70 cartridge in 1873. (00:09:20)
Continuity mistake: When Ziva dumps the four bundles of $100.00 bills on the bed, they all land face up. Then the scene changes to Tony taking a picture of them. Back to the bundles, and now only three are face up and one is face down, with no one touching them. (00:10:40)
Factual error: Abby says she ran X-ray chromatography. There is no such thing. I assume she meant X-ray crystallography.
Visible crew/equipment: After McGee tells Gibbs that he overheard the mention of "Paraguay" during the private conversation between Ziva and Gibbs, when it cuts to the next shot just as Ducky joins Kasie in the lab, the orange tape mark and yellow T-mark are visible on the floor. (00:29:20)
Continuity mistake: We see a close-up of Kevin's poster that Ziva is holding. In the close-up, she is holding the poster on the right-hand side. When the shot changes to a wider shot showing Ziva and Tony, Ziva is no longer holding the poster on the right-hand side, but is now holding it on the bottom. (00:04:40)
Factual error: The "bullets" extracted from the victim are intact cartridges, not fired bullets with no cases. (00:12:36)
You Better Watch Out - S10-E10
Continuity mistake: When Jimmy is talking about the smell of dead bodies, his mask is either on or off depending on the shot. (00:02:40)
Continuity mistake: In the evidence locker, Ziva opens a folder and the white notepad is on the left-hand side. Camera changes to behind her, and now the white pad is on the right. (00:26:40)
Continuity mistake: When DiNozzo is asking, "When was the last time Ms Fenton saw Mr Kersey?" his hand is constantly changing position between instant cuts. (00:13:10)
Continuity mistake: When we first see young Abby, the way she's holding her bear changes between shots. (00:04:50)
Continuity mistake: Abby says that McGee is the most helpful person with clipboards. When she does, the position of the clipboard in her arms is constantly changing between instant cuts. (00:03:30)
Continuity mistake: When Tony wakes Ziva up, he grabs her wrist, and her fist is clenched in one shot and open in the next before returning to the closed position. (00:22:00)
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.