I understood there were lights on all over the place, but the curtains were shut in the boys' bedroom and the bathroom.
Given the whole debate about seeing someone in the master bedroom, I thought the curtains were, as in the photos, open in there - otherwise they would just have refuted that claim by saying the curtains were drawn instead of "it was a trick of the moonlight". In which case I'm surprised no-one thought it odd that June and Nevill were sleeping with the curtains open.
Presumably the curtains had to be open in the kitchen for the police to approach the window and look through it.
Given the light was on in the boys' bedroom, it's perhaps more likely that light and the neighbouring bathroom light were put on by the killer: the boys wouldn't have been sleeping with the bedroom light on. But presumably the killer wouldn't have put the light before killing the boys or that would have woken them up. Personally I think the killer went around the house afterwards doing the extra head shots to make sure they were all dead after being surprised by how much effort was required to kill Nevill, and that might have been when the boys' light was put on.
If it is the case that the lights were on inside the house and there were curtains open in rooms where murders took place, Bamber would have been taking quite a risk if it was him who committed the murders - which also seems at odds with someone who is committing a murder they have coldly planned and they intend not to get caught. It seems to me the person inside didn't care if anyone outside could see what was happening in the house. Which as you know, makes me suspect it was Sheila.
Good points there. Kitchen light was on and I think that they may have mistaken Neville for a female. Maybe some of the cushions etc too could have made it look like two people. I don't think Sheila was there.
I do wonder about the possible movement seen upstairs, though.
Neville's bedroom curtains probably were left open. They went to be bed when it was dark and I doubt there would be much in the way of lights outside in the country. They would also be up at the crack of dawn and kept a window open in the bedroom, so why close the curtains as they would blow about. As you say, if someone had meticulously planned the murders, they would have known about the open curtains, so were taking a mega risk. If it was on the other hand a frenzied attack by a mad man/woman, then it makes more sense.
The twins couldn't have been shot in the dark, so the murderer would have to have put the lights on, or did he use the light from the bathroom or hall?
Did Jeremy ever read the bible? would he know the appropriate Psalm?
A photograph of the Bible showed that it was open at Psalms 51–55, a section of the Bible relating to wickedness and mercy, of which the following quotations can be found:-
Wash me thoroughly from mine iniquity, and cleanse me from my sin
Save me from blood guiltiness O God
My heart is sore pained within me and the terrors of death are fallen upon me.
Examination of the blood staining on the pages of the Bible confirmed that it was this page which the book was open on.
I don't think that Jeremy actually committed the murders, but I am still unsure about Sheila.