An Australian woman has been jailed for life, with no chance of release for at least 33 years, for murdering three relatives and trying to kill another with a toxic mushroom meal.

The jail term, one of the longest ever handed to a female offender in Australia, means Erin Patterson, 50, will be in her 80s before she can apply for parole.

A Supreme Court judge said Patterson's crimes were the 'worst category' for offending and involved an 'elaborate cover-up'.

Patterson killed her in-laws Don and Gail Patterson, both 70, and Gail's sister Heather Wilkinson, 66, after serving them a toxic beef Wellington at her home in Victoria in 2023.

Heather's husband Ian Wilkinson, a local pastor, survived the lunch after recovering from a coma and has ongoing health issues related to the poisoning.

Patterson's estranged husband Simon Patterson was meant to attend the lunch too but cancelled at the last minute, in part due to his belief that his wife had been trying to poison him for years.

Patterson has long maintained her innocence, saying the toxic death cap mushrooms in the dish she prepared were accidentally added and that she never intended to harm her relatives.

Justice Christopher Beale pointed out that the prosecution had not alleged a motive for Patterson's crimes during the nine-week murder trial, which wrapped up two months ago, and that he would not either.

'Only you know why you committed them,' he said, in reference to the three murders and the attempted murder. 'I will not be speculating about that matter.'

During his sentencing remarks, Justice Beale noted that Patterson's reputation and the public interest in her case meant she would likely remain a notorious prisoner, facing risk from other inmates in her female maximum security prison.

The judge summarized Patterson's actions as showing no remorse, stating, 'Your failure to exhibit any remorse poured salt in all the victims' wounds.'

Outside the court, Ian Wilkinson, the sole survivor of the fatal lunch, thanked the police, prosecutors, and medical staff who treated the victims and encouraged kindness among others.

Patterson has 28 days to lodge an appeal against her sentence and the guilty verdicts.