So, on 9th August 1985, not only do police know about one of the silencers, they already have possession of one (SBJ/1), and what is more, the police let Jeremy know that they know about the existence of the silencer before they hand the keys to the farmhouse back to the family, later that same evening...
So, if Jeremy was the killer, why did Jeremy allow the police to give the keys to the farmhouse over to the relatives, who despised Jeremy?