There was a discussion a little while ago and someone (possibly Caroline) pointed out the fact that the blood on the open pages of the bible was on the wrong page, i.e. it was on the page furthest from Sheila's arm.
If you look at this picture:

The pages of the bible do not appear to be completely open, they're scrunched up underneath it. So, for blood to be where it was on the pages, wouldn't the bible have had to be page side up? And then the transference of the blood to create the mirrored stain on the other page would have taken place as the bible was placed on the floor.
This may make more sense if someone could post the picture of the open pages, which I can't find at the moment.