Australian Erin Patterson found guilty of murdering three of her estranged husband's relatives by deliberately serving them poisonous mushrooms for lunch.

A court in Australia on Monday convicted Erin Patterson of murdering three elderly relatives of her estranged husband with a meal laced with poisonous mushrooms as one of the biggest criminal trials gripping the country concluded.

Mushroom killer Erin Patterson has been found guilty after a trial with sentencing coming later - she had poisoned relatives with beef wellington.