I can go along with that David for the simple fact that it was so obvious as to the intentions of the relatives.
Ann Eaton is the logical suspect for planting the scratch marks.
1. She knew where the silencer had come into contact with the mantle shelf before anyone else.
2. Julie had told her about Nevils injuries after the mortuary visit.
3. DC Clarke had told her where Nevils body was found.
4. She would have seen the blue coat hanging over that area of the mantle shelf. Obscuring it from crime scene photos.
5. She had unlimited access to the scene from the 9th of August onwards.
6. The scratch marks helped erase a substansial debt to Jeremy and enabled her to become director of Osea caravan park.