I've just been having some further thoughts about the events of June 16. After looking at the house floor-plan thread (huge thanks to Hercule/Steve etc. for this work) it's possible to get a clearer picture of access in/out of the house/garage/back yard.
I am assuming that the A's garage door can't be remotely operated from outside, and so they have to first enter by the side garage entrance door and then open the main garage door from inside before driving their car(s) in. So, on June 16, KC returned to the house after GA had left for work and most likely used her own key to gain entry to the house via the garage entrance door (the A's have stated that this is the normal/usual way they enter the house). She most probably also left her car on the driveway as she was not supposed to be there (told GA she was off to 'work') and so would be leaving again at some point.
I will also assume that the account (from CA/GA) of the pool ladder being up and the gate being left open on one particular day is true, and that the day this occurred was June 16. I had previously thought that the gate they referred to was a gate for an enclosure that contained the pool for safety reasons, but have now seen in the available pics that there is no such enclosure and so the gate they referred to must be the one in the side fence of their yard, next to the garage, that leads to the front of the property.
Since it doesn't make sense to have the latch of this gate on the outside of the fence, it must be that the gate can only be opened, and fastened shut again, from the inside, so it's feasible to assume that the reason it was not fastened shut was because the person who had last used it had exited the back yard and did not go back via the house and backyard to refasten it from the inside. I think the reason for this was because that person was in a hurry to leave the property.
But, according to CA/GA, the gate was not only unfastened, but was left open. I think this is because whoever used the gate on that occasion was a) carrying something using both hands/arms, and b) in a hurry to get that 'load' into the car and away.
So, if Caylee died inside the house, I would expect KC to have carried her straight out through either the main front door, main garage door or side garage entrance door and to the car– there would be no reason to exit through the side yard gate, thus leaving herself unable to refasten it. Conversely, if she died in the back yard, would it make sense for KC to then carry her in through the house and out to the car via any of the exits as above, when the shortest, quickest route was through the side gate? This leads me to believe that Caylee did indeed die in the back yard. I think just after deciding to flee, KC may have gone into the house to get a covering and bag to wrap the body with and to collect her things. She probably then went out the side garage door, put her things into the car (possibly also anything else that she needed to take away from the 'scene'), and then opened the trunk. I think she then returned to the house, locking the side garage door from the inside, and then went out to wrap Caylee's body in the back yard. She then carried her through the side gate, into the trunk and away as fast as possible – no time to close the gate, and impossible now to refasten it.
Finally, if June 16 was indeed the day that the gate was left open, it was also the day that the pool ladder was left in place. Why was this? I'll leave that for others to theorise on, but I'm sure by now it's clear what I think the answer is!