The door to Mary Kelley's residence at 13 Miller Court was locked when the corpse inside was discovered. In my opinion, an intruder would not have bothered to lock it (even less so, getting possession of the key); whereas the rightful occupant would have both the key and the established habit of locking the door upon leaving. I think this evidence goes to confirm a my hypothesis that Mary Kelly, having slain the Ripper earlier, walked away from her home and, some hours later, off the stage of history forever.