My understanding is that her boyfriend-of-the-day, Tony, would not allow Caylee to spend the night at his condo. I think we can all extrapolate what happened next -- Xanex (which didn't work on Caylee anymore) and then Chloroform and spending the night in the trunk of Casey's car. The duct tape was extra insurance that nobody heard Caylee's cries.
Xanax = Zanny the Nanny
Based on that it could easily have been an accident that she tried to cover up. Perhaps the jury will struggle with the premeditation piece.