So what motive does Sheila have for killing her boys? Either she's in control of her faculties(as it's my case Jeremy was when he killed his family),she destroys anyone and everything who comes in her way including Nevill which would explain the cut-off telephone call,or she's in psychosis and hasn't a clue what she's doing or the consequences.
I put it to you that Sheila was not the vindictive type,she was squeamish at the best of times and was guilty no more of indolence and wanting to hook a rich man as a husband after Colin left her.
There doesn't have to be a motive as such,Steve. It's that their minds and way of thinking is a lot different to ours. Their thought mechanism is, at the most part,irrational and overstretched out of all proportion no matter how much you try and reason with them.
It's made worse by the fact that they're renowned for missing doses of medication or not taking it at all,,,and when these things happen,,,they're at their most vulnerable and dangerous.
As it was,,Sheila was missing medication and also appointments at clinics/hospital or GP,,quite possibly because she was taking other drugs which,as I've said before,,cancels out the benefit that her medication for psychosis was meant for.
Just how long she'd been taking cannabis and cocaine for,,nobody knows,,,but it was absolutely futile to think that her medication was doing any good while she was taking the other stuff,,,because there'd have been no effect or improvement to her illness.
I often wonder if Dr.Ferguson knew of her drug use coupled with her medication.