Patterson was found guilty last year of murdering her husband’s parents and elderly aunt, deliberately lacing their beef Wellington meal with highly toxic death cap mushrooms.
The 52-year-old maintained her triple murder convictions were a “miscarriage of justice”, urging the Court of Appeal in Victoria state to either set her free or have the case heard again.
The court found the killings were “carefully planned and deliberate”, and there were insufficient grounds to try the case again.
“This offending was extraordinarily cold and calculated,” judge Stephen McLeish said.
“It stands to be denounced in the strongest terms.”
Patterson has also been convicted of the attempted murder of her husband’s uncle, a small-town local pastor who survived after weeks in hospital.
The court not only threw out Patterson’s appeal, it also found that her original jail sentence did not match the gravity of her crimes.
Patterson was initially eligible to apply for release after 33 years.
The court ruled that she should not be eligible for parole, meaning Patterson is likely to die in prison.
Patterson did not front the trial in person, instead watching proceedings via video link from a maximum security prison on the outskirts of Melbourne.
Her lawyers had alleged a litany of irregularities in the trial, including an “oppressive” cross-examination and unfair decisions on the admission of evidence.
Prosecutors argued that the non-parole period of 33 years imposed by the judge was “manifestly inadequate”.
They said 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.
Patterson’s trial last year drew podcasters, film crews and true crime fans to a courthouse in the rural town of Morwell, a sedate hamlet in Victoria better known for its prize-winning roses.
Audiences from New York to New Delhi followed every twist of what many now simply call the “mushroom murders”.
The motive of the killings remains a mystery.
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)
