Continuity mistake: When Gibbs is walking away from the FBI agent at the start, he is approaching a tree. As the camera changes he is way past the tree. (00:04:50)
Visible crew/equipment: After Gibbs explains to Agent Reyes that Commander Shields in on Terminal Leave, and she has a four day deadline to solve the case, when Gibbs walks away there's an overhead shot and multiple chalk T-marks are visible on the ground. (00:05:00)
Visible crew/equipment: When Mr Palmer is analyzing the blood, we see Dr Mallard by the fridge. If you look closely you can see the boom pole reflected in the door. (00:06:00)
Continuity mistake: When Ducky is doing the autopsy on the dog, he talks to the dog and leans against the slab on his elbows (the elbows are not seen however the motion is easy to distinguish). Camera cuts and his arms are wide and he's resting on his hands. (00:07:50)
Continuity mistake: When Gibbs catches McGee playing games on the MTAC system, McGee's microphone is down by his mouth. Camera cuts and it's up out of the way, instantly. (00:18:30)
Continuity mistake: When McGee turns up at the house, Dinozzo puts his hand on McGee's shoulder. Camera cuts and it's no longer there. (00:26:30)
Continuity mistake: When Gibbs is making the phone call to (presumably) the press, he is holding the receiver in his hand. Camera cuts and now his hands are on the desk. (00:31:50)
Factual error: Abby says she ran X-ray chromatography. There is no such thing. I assume she meant X-ray crystallography.
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.