Seems like the tripping by Natalee was the first I heard about a "black security guard" assisting her followed by the arrest of the two guards.
Every lie can have a kernel of truth.
Perhaps she tripped getting out of the car, whereever it was that they took her. Perhaps the date rape drug was kicking in pretty strong. Perhaps she was trying to get away in rocky terrain.
I think she tripped. But not like they said.
And perhaps the "tripping" was to explain a sometime in the future discovery of injuries on her body. "Oh she fell and fractured her skull before she fell asleep on the beach and was carried out into the ocean, or fell in a cistern, or whatever"
Saying "she tripped" has alot of meaning, just not what they are saying.