Interesting that he wants to know if the police know what order the family members were killed.
It's like he was fishing for information, to see how much the police could tell from the crime scene.
I wonder what the accountant would have said if the police had followed that up.
Obviously at the time Bamber asked the police that question he wasn't yet a suspect. It seems like an odd thing to ask, especially as he refused to tell the police why the accountant would need that information.