The missing piece of toenail belonging to Sheila,,which was found downstairs,,,would have been damaged by the recoil of the rifle. Nobody has made the suggestion that she'd have been holding, and firing the rifle to have done that. There would have been bleeding from that alone,,, if the nail was torn from the nailbed.
Would not that also have been proof on its own that she had the rifle,,and injured her own toe with it.?
Nobody else is going to shoot someone in the toe.