Well do make it explicit. Jeremy had time to fix the scene as he wanted,whether it was tossing a bible onto the body,digging one of Sheila's false nails from her vanity bag into Nevill's flesh or placing her hand on the shotgun after death. He had many months to plan things out(Stage 4 of catathymic crisis)..
I feel quite certain that if you or I search hard enough we'll find a syndrome suffered by those who have a deep need to find evidence, however implausible, to fit ludicrous scenarios of their own making. Sadly, like all personality disorders, there's no cure
