Most inheritence killers are not forensically aware. Not so much now as there is so much available information. However they escalate from nothing to murder.
In Jeremy's case, his biggest crime was the caravan break in. Where he threw a few papers around & thought everyone would believe it was a burglar. Doubtful Nevill believed him but at the time he was not prosecuted.
On the 7th August he felt rifle on Sheila, windows shut, tell EP Sheila is a looney - home free.