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The Truth Is Out There - S1-E17
Revealing mistake: Gibbs finds a bunch of cash hidden in the victim's speaker. "For Motion Picture Use Only" is printed on them.
A Weak Link - S1-E22
Revealing mistake: When Gibbs and Todd are walking into the church, the camera shadow can be seen going over the seats on the left hand side. There is no-one other than Gibbs and Todd moving and the shadows are not possible from them. (00:25:00)
Revealing mistake: When the team run from the Captain's office at sunset, Gibbs closes the door as the last man out. However, a shadow can still be seen to move over the door. We know there is no-one else in the office. (00:38:05)
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Revealing mistake: Just after Agent Todd is seen going through the diary, there is a shot of the ship sailing past the camera. However the number 51 on the side of the ship is backwards, showing the shot is flipped. (00:30:20)
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.