An Australian woman convicted of killing three family members with poisonous mushrooms has been ordered to spend the rest of her life in prison after an appeals court ruled that her crimes were too grave to justify any possibility of release.

The three-judge appeals court on Friday rejected Erin Patterson’s attempt to overturn her conviction, describing the murders as extraordinarily cold and calculated and ruling that her original sentence was too lenient.

Patterson, 52, was convicted in July 2025 of murdering three people and attempting to kill a fourth after serving a beef wellington meal laced with deadly death cap mushrooms at her home in July 2023.

Her victims were her estranged husband’s parents, Don and Gail Patterson, and Gail’s sister, Heather Wilkinson. Heather’s husband, Ian Wilkinson, survived after spending weeks in hospital.

Although Patterson had initially received three life sentences and another 25 years for attempted murder, she was given a 33-year non-parole period, which meant she could become eligible for release in her 80s.

The appeals court, however, ruled that the severity of the offences made it inappropriate to set a minimum period before which she could seek release.

“In all the circumstances, after anxious consideration, we have concluded that the case involved such shocking criminality that it is inappropriate to fix a non-parole period,” Justice Stephen McLeish said.

Patterson’s lawyers had advanced seven grounds of appeal, seeking to have her conviction overturned and a retrial ordered.

One of their major arguments concerned the arrangement for keeping jurors together during the trial in Morwell, Victoria. They argued that jurors sharing a hotel at different times with prosecutors and witnesses created a risk that their impartiality could have been compromised.

The judges rejected the argument, saying there was no objective basis to believe that the jury had failed to reach its verdict according to the law.

The court also dismissed objections to the admission of cellphone evidence which placed Patterson near locations where death cap mushrooms had been reported on a citizen scientist website.

CNN reports that the judges held that the evidence was admissible as part of the prosecution’s wider circumstantial case.

The case arose from a family lunch Patterson hosted at her home in July 2023, where she served beef wellington to four guests.

Within hours, the guests developed severe stomach pains, while three later died from mushroom poisoning.

Although Patterson admitted preparing the meal, she maintained that the poisonous mushrooms had entered the food accidentally while she was trying to improve its flavour.

Prosecutors, however, argued that she deliberately selected the mushrooms for the killings, dried them in a dehydrator and later disposed of the appliance as her guests battled for their lives in hospital.

The jury accepted the prosecution’s case, leading to her conviction and the subsequent life sentences.

The ruling brings another major legal setback for Patterson in a case that has attracted international attention because of the unusual method used to carry out the killings.