Erin Patterson's conviction for the deaths by poisoning of her estranged husband's relatives has prompted fevered speculation across Australia about her motive.

An Australian woman was on Monday convicted of murdering three elderly relatives of her estranged husband with a meal laced with poisonous mushrooms, and attempting to murder a fourth, in a case that gripped the country.

The jury in the Supreme Court trial in Victoria state returned a verdict after six days of deliberations, following a nine-week trial that gripped Australia.