Charges have been dropped, prejudicial assessment is a potential risk/result of the lack of evidence regarding the poisonings of Simon.
“…the source of Simon Patterson’s gastrointestinal disturbance is empirically undeterminable, any such inference would be weak.”
I agree.
As I've opined here before, had that case proceeded, and in light of the conduct of the defence of the murders case by Mandy, IMO prosecuting the charges would have been an uphill battle to return a beyond reasonable doubt conviction.