What I see is two people coming back from the pool after a morning swim. The mark on the wall is IMO a reflection of the lady. It isn't a shadow as there is not enough light to form shadows.
If I'm right that it is a reflection off a relatively rough surface, then the angle of incidence = angle of reflection. Then if we can work out where the person who took photo was standing then because the "image" appears to be on a line directly below end of the wall of the apartment we could make the calculations of where they are standing in the photo.
I have enlarged the image by x 300 and IMO, the blue thing that is being carried is an inflatable swimming ring.
The couple were just past the apartment and about a metre past the front door on this image, so they were about 10 metres back from the crossing that Jane remembers Tannerman making.
She and the officer together estimated that she was about 5 metres from Tannerman when she first saw him,
so I am ammending my position of Jane relative to these two people as more than 5 metres farther up the road than they are.Please do not forget that Jane remembered him crossing the road and carrying straight on + the wall has a large curve in it at the top, meaning that the top 3 metres of wall is not visible on that photo. The place that Tannerman walked across has to be worked out as accuaretly as posible using GE.