Patterson, 51, was sentenced to life behind bars after she killed her three lunch guests by serving them beef Wellingtons laced with death cap mushrooms in July 2023.
But Victoria's top prosecutor Brendan Kissane KC is challenging her 33-year minimum term that makes her eligible for parole in her 80s.
The sentencing judge rightly found Patterson's crimes were a cruel betrayal and the worst case of murder, Mr Kissane told the Victorian Court of Appeal on Thursday.
But the prosecutor argued the judge made a mistake giving Patterson a chance at walking from prison.
"It was not open to His Honour to fix a non-parole period in this case when it involved three murders, one attempted murder and significant circumstances of aggravation," Mr Kissane said.
Even if the court was against him, Mr Kissane still submitted 33 years was manifestly inadequate.
He argued the sentencing judge wrongly determined Patterson would likely be held in solitary confinement for years to come.
Mr Kissane pointed to the fact Patterson had access in prison to the library, leisure equipment and the chaplain.
But Patterson's barrister Richard Edney argued the sentencing judge was correct to find she was experiencing solitary confinement.
The judge made clear and "impeccable" sentencing remarks that the court should not overturn on appeal, Mr Edney said.
"He has clearly taken into account all relevant considerations," the barrister said.
"In our submission, the sentencing judge did everything right in this complex sentencing exercise."
Patterson is separately fighting to quash her murder convictions, arguing she suffered a substantial miscarriage of justice.
One of her appeal grounds is that she was forced to give evidence at trial because the trial judge excluded mushroom photos.
Her barrister Veronika Drago pointed to the judge's decision to not allow the photos from 2020 found on Patterson's SD card into evidence.
The defence wanted to use those photos to show Patterson always had an interest in foraging for mushrooms, Ms Drago said on Wednesday.
Without the images, the only way jurors could hear evidence of foraging was through Patterson, the barrister argued.
But crown prosecutor Jeremy McWilliams refuted that claim on Thursday, saying Patterson seemingly always intended to give evidence.
He noted there was no evidence Patterson had previously foraged, citing her police interview, in which she denied any interest.
Mr McWilliams referenced statements from Patterson's family and friends who did not have recollections of her foraging.
But Patterson's trial barrister submitted in his opening address that she had lied in the police interview and she always had an interest in foraging, Mr McWilliams said.
"(Patterson) would need to give evidence about those matters given the evidentiary landscape," the prosecutor said on Thursday.
"Both to overcome the lie but also the suite of evidence that tends to support the lie."
Mr McWilliams denied that simply tendering the photos to the jury would have been sufficient.
The prosecutor also refuted the claim Patterson's cross-examination was unfair and oppressive, arguing the trial prosecutor had been fair and careful.
"Plainly, we reject any suggestion the prosecutor acted as anything other than a model administrator of justice," Mr McWilliams said.
A jury found Patterson deliberately served beef Wellingtons laced with death cap mushrooms to her former in-laws Don and Gail Patterson, 70, and Gail's sister Heather Wilkinson, 66.
The three guests died after the July 2023 lunch at Patterson's Leongatha home, in regional Victoria.
Heather's husband Ian fell seriously ill from the meal but survived.
Patterson was also convicted of Mr Wilkinson's attempted murder.
Mr Wilkinson and other members of the Wilkinson and Patterson families were back in court on Thursday, alongside members of the public and dozens of journalists.
Justices Stephen McLeish, Lesley Taylor and Peter Kidd will hand down their decision on the two appeals at a later date.
12°C