The above quote from the 2002 appeal highlights some interesting facts.
It is human DNA inside the silencer. As it is impossible to put a finger inside the silencer, I am not sure how human DNA got inside, apart from a contact shot.
It says there was DNA from a male and female. This matches the blood evidence which suggests it could be Neville and June' blood.
The 2002 appeal later goes on to say the DNA was likely to be June's.
With human blood and DNA inside the silencer, even if neither was Sheila's, it still highlights Bamber as the killer. As Sheila would not bother putting the silencer away. Bamber had reasons to put the silencer away, as a recent thread showed.