The evidence is the silencer was on the rifle.
But agree if it wasn't, Sheila could have shot herself.
Hang on a minute!
First of all, Sheila did not shoot herself! Secondly, Jeremy Bamber did not shoot her! Thirdly, as demonstrated during the 'Birdwell Armoury' experiments, Sheila could have shot herself technically with the silencer fitted to the end of the anshuzt rifles barrel, it was not too long so as to exclude several different ways of her shooting herself with the silencer fixed!
The key issue, was not whether she could have shot herself with the silencer fitted, but rather 'who took the silencer off'?
Cops took the silencer off when Sheila's death scene was staged during 'informatives', then later that same morning, DS 'Stan' Jones returned to the farmhouse to seize it ('SBJ/1'), its documented that he did...
On that very same occasion, 'Stan' Jones seized or took three other exhibits, bearing his identyfying marks, 'SBJ/2', 'SBJ/3', and 'SBJ/4'...