457. Mr Fletcher, the firearms expert, gave evidence to explain how blood got into the moderator if it was attached, or into the barrel if there was no moderator attached. He said that the mechanism was complicated and not then fully appreciated. However, the expanding gas when the bullet left the muzzle was under normal circumstances distributed into the atmosphere. However with a contact shot there was no opportunity for this escape and the gas would follow the bullet into the wound as it expanded. Back pressure would then build up forcing the gas back out of the wound taking with it blood and tissue which would in effect be blasted back into the barrel if there was no moderator or into the moderator if one was attached. He said that even without direct contact, the same effect might occur but only if the gap between the end of the barrel, or the moderator if attached, and the skin was less than one millimetre. He said that the likelihood of such an occurrence was to an extent dependent on the part of the body to which the shot was delivered and the amount of blood present at that point.
458. If the shot to Shelia Caffell, which was a contact shot to the throat, had been fired without the moderator in place, he would have expected to find blood in the barrel of the gun. If the moderator was attached it was "virtually certain" that Sheila Caffell's blood would get into the moderator. There was, he said "a very slight possibility of it not happening, but very slight".
http://www.homepage-link.to/justice/judgements/Bamber/index.html
In other words ... if Sheila had shot herself blood would have been drawn back into the barrel of the gun. If someone else had shot her using a silencer that draw back would have taken Sheila's blood into the silencer.
Sheila's blood was found in the silencer. Someone shot her. And the only person that could have been was Jeremy Bamber.
Do you think I haven't pored over this with a magnifying glass?!
It wasn't "virtually certain" at all that blood would deposit in/on the barrel if the silencer wasn't attached.
From a book authored by Dr Vincent DiMaio - The Pathology Of Gunshot Wounds:
Page 326
"Absence of blood on or in the barrel does not preclude a close range or contact wound".
https://en.wikipedia.org/wiki/Vincent_Di_MaioBrie my challenge to you: find a case, test fire, forensic research, absolutely anything, where blood is found inside a silencer as a result of the 'drawback' phenomenon. I'll give you a clue the physics behind the whole proposition make it impossible.