So when do you think the window was opened ? Before Gerry entered the apartment in case the abductor needed an escape route or after, when there was a perfectly accessible, and less conspicuous, door to use ?
Window
and shutters?
The window may have been open (or partially open) at that stage without the shutters lifted (too much noise to alert someone coming up the steps and not enough time to get out anyway).
What disturbs me is that the window / shutter issue could have been a red herring for anyone who could have been traced to a key. Not necessarily a staff member, but someone associated with one; or quite simply someone who could have stolen various keys, made copies and put them back where they were supposed to be before the person who had legitimate access noticed.
What disturbs me further is that the investigation seemed more interested in where the photographic paper came from (a legitimate line of inquiry, but which could have been easily resolved much earlier) than duplicate key issues.