The 51-year-old was found guilty last year of murdering her husband’s parents and an elderly aunt in 2023 by serving them a beef Wellington lunch laced with lethal death cap mushrooms.
Patterson was also convicted of the attempted murder of her husband’s uncle, a small-town local pastor who survived the beef-and-pastry dish after weeks in hospital.
A judge sentenced her to life imprisonment, eligible for parole after 33 years.
Her lawyers sought on Wednesday to overturn that conviction, alleging a litany of irregularities and the misuse of evidence during her trial.
Lawyer Veronika Drago argued that some evidence allowed by the judge — relating to cell towers and posts of death cap mushroom sightings — was “innocuous” and unreliable.
Obliging her to answer questions based on this evidence “arises to the level of a substantial miscarriage of justice”, Drago said.
Other evidence about mushroom images on a memory card in Patterson’s home was wrongly excluded, her defence said.
Patterson watched the proceedings at Melbourne’s Supreme Court via a live video link from her maximum-security prison, the Dame Phyllis Frost Centre in Melbourne’s western suburbs.
She was wearing a blue prison jumper, national broadcaster ABC said.
Her other defence lawyer, Richard Edney, said there was “unfair and oppressive” cross-examining of Patterson during her trial.
Edney also argued that the fact that members of the jury had stayed in the same hotel as a witness for the police — as well as members of the prosecution — undermined the fairness of the trial.
He said it represented a “fundamental failure” of the legal process “in perhaps one of the most high-profile criminal trials this state has ever had”.
However, he conceded there was no evidence to suggest the jury had communicated with others.
Prosecutor Brendan Kissane said in response that placing the jury in the hotel was an “accident”.
The prosecution also defended the use of evidence intended to demonstrate that Patterson had been able to source the deadly mushrooms before the fateful lunch.
The three judges will also hear an appeal on Thursday from the prosecution seeking a stiffer sentence.
Prosecutors have said the non-parole period of 33 years imposed by the judge was “manifestly inadequate”.
They say the judge erred in finding there was a substantial chance Patterson would be held in solitary confinement for years to come, and this “infected” his decision on parole.
A 12-person jury found Patterson guilty in July last year of murdering her husband Simon’s parents, Don and Gail Patterson, as well as his aunt, Heather Wilkinson, at her home in the Victorian farming village of Leongatha.
She was also found guilty of attempting to murder Heather’s husband Ian, a pastor who fell gravely ill but eventually recovered. (AFP)
