Speculation is brewing over the intentions of the woman who cooked up a deadly mushroom lunch in Victoria

Gail and Don Patterson and Gail's sister Heather Wilkinson died after having lunch at their ex-daughter-in-law Erin Patterson's home.

Heather's husband, Ian, remains in a critical condition.

Australian correspondent Murray Olds says the ex-husband of the woman, Simon Patterson, claims she once tried to poison him.

"Simon suspected he'd been poisoned by Erin, because he spent three weeks in intensive care." 

Forensics are underway on a food dehydrator found at a dump near the house.

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