Visible crew/equipment: While Gibbs is in the lab reviewing the toxicology report with Abby she notes the organic red dye. When Gibbs heads to the door, just as Abby asks if he wants to know how Diego died, the pink T-mark is visible on the floor where Gibbs stands. (00:25:05)
Visible crew/equipment: While Gibbs is at the diner with Dr. Taft and his wife he gets a call from Ellie, and when it cuts to the overhead shot of Gibbs, Ellie, and Tony walking toward each other, on the ground we can see the reddish chalk mark (for Gibbs) and two white chalk T-marks (for Tony and Ellie) where the three actors meet. (00:26:10)
Visible crew/equipment: When "Nanook" stands beside his desk while he tells Tony and Ellie about Delilah's mother, there's a blue T-mark on the floor by McGee's feet. (00:03:05)
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.