These are the things which lead to his arrest & charge.
He would not be aware of GSR or back spatter. Besides which, would the police bother checking after he had insinuated Sheila so impressively?
He felt Julie would not turn after a month. But she did.
Some of these things Bamber would be expecting the police to look at - kitchen fight, Sheila's condition. However other evidence meant a more detailed investigation into these took place.