im no M.E. but a few things come to mind, i have removed deceased people in this position that Nevill was found in, its possible he was still alive while in the chair and was left to die, his age , would have speeded up rm, its not always possible to flex limbs not all the time, if he was left to die jeremy must be innocent sheila could have used the last few hours to check from time to time , remember she could have tested for death , there was no need to confirm it because she would die also, a killer could not afford to wait,the gamble would be too great , lastly, because if jeremy was inside he would not have the outside on his mind, all it would take is unknown to him someone could have called the police because car theivs were on his land one knock on the door and its over think that over.