It seems it wasn't until the 13th of sept or shortly after,that a biologist wanted to examine the baffles of the silencer for blood,this was after it was re-admitted for testing around the end of Aug.
This was after Julie went to the police and after Bambers first police interview!
Apparently the inside wasn't tested when the silencer was first examined around 13th Aug,only the outside for some reason before being taken elsewhere for fingerprinting!
So,anyway,it wasn't until Julie went to the police that the baffles were tested and Sheila's blood grouping was found!
Mmmmmm!!