You know when a train of thought takes you somewhere weird? I was musing earlier and now I'm wondering this:
Can you contest a Will, on the basis that the deceased had lost capacity, but if they hadn't they'd have changed the Will themselves?
My (admittedly dark) musings were as follows:
Say we have a couple, the wife has a couple of children, and later marries a man who becomes their stepfather. In old age, the wife/mother loses capacity - her Will leaves everything to her husband.
But before the wife/mother dies the stepfather kills his now adult stepchild. (told you it was dark 
)
The wife/mother knows nothing of this, having lost awareness of the world around her. But one could reasonably think if she was aware, she would not want to leave everything to her child's killer.
Does anyone know, would that be a legal basis to contest the Will? Or is there a mechanism to allow the Will to be changed even though capacity is lost?
I know if you murder someone you can't profit from the crime, but I'm not sure this would come under that.