Erin Patterson was sentenced to three life sentences and 25 years for attempted murder on Monday for killing three family members in July 2023.

Erin Patterson (C) leaves the Supreme Court of Victoria in Melbourne, Australia, on Monday, when she was sentenced to three life sentences plus 25 years. Photo by Joel Carrett/EPA UPI

Sept. 8 (UPI) -- Erin Patterson, the Australian mother convicted last month of killing her estranged husband's parents and aunt by serving them a dish containing poisonous death cap mushrooms, was sentenced to three life sentences plus 25 years for attempted murder on Monday.

The sentences are to be served concurrently with a non-parole period of 33 years, Justice Christopher Beale of the Victorian Supreme Court said during sentencing, which was broadcast live.

"Fixing a non-parole period is not to undervalue the horrendous nature of your offending," he said. "Your total effective sentence will be life imprisonment and the period during which you will be ineligible for parole will be a very substantial one."

Patterson, 50, was convicted by a jury in July for killing Gail and Don Patterson, the 70-year-old parents of her now ex-husband, Simon Patterson, and his 66-year-old aunt, Heather Wilkinson, and attempting to kill Heather's husband, Ian Wilkinson, on July 29, 2023.

The method was poisonous death cap mushrooms that she cooked into a lunch and served them at her home in Leongatha, Victoria.

"Your offending involved an enormous betrayal of trust," Beale told Patterson during sentencing. "Your victims were all your relatives by marriage. More than that, they had all been good to you and your children over many years, as you acknowledged in your testimony.

"Not only did you cut short three lives and cause lasting damage to Ian Wilkinson's health, thereby devastating the extended Patterson and Wilkinson families, you inflicted untold suffering on your own children, whom you robbed of their beloved grandparents."

Authorities said her target was her estranged husband, who did not attend the lunch.

During the nine-week trial, prosecutors built a case showing that Patterson had planned the murder, deliberately picking the mushrooms from locations she learned about online, dehydrating them and then turning them into a powder that she served to her guests in a beef Wellington.

The jury heard she had enticed the family to her house by faking a cancer diagnosis and then feigned being sick along with the rest of her guests.

Ian, who became sick after eating the meal, survived.

During remarks to the press outside the courthouse, Ian thanked authorities for their work on the case.

"They made a professional, efficient and effective investigation into what happened at the lunch," he said. "They brought to light the truth of what happened with the death of three good people. We're grateful for their skills that brought this truth to light."

In handing down his sentence, he declined to enforce the harsher penalty of life in prison without the possibility of parole, as the prosecution was seeking.

In explaining his reasoning, Beale said Patterson had been held in continuous solitary confinement for the last 15 months and there was "a substantial chance" that, for her own protection, she would be held there for years to come.

"The harsh prison conditions that you have experienced already and the likely prospect of solitary confinement for the foreseeable future are important and weighty considerations which should count for something in the sentencing exercise," he said.

"In my view, the only scope for making them count is by fixing a non-parole period."