Prosecutors in Australia have filed an appeal against the sentence of mushroom murderer Erin Patterson, saying it was “manifestly inadequate”.

Last month Patterson, 51, was jailed for life with no chance of release for at least 33 years, for murdering three relatives and trying to kill another with a toxic mushroom meal.

On Monday, the deadline for the appeal, the Department of Public Prosecutions (DPP) confirmed that it had filed an appeal “on the basis that the sentence handed down to Erin Patterson is manifestly inadequate”.

Patterson’s jail term – one of the longest ever handed to a female offender in Australia – means she will be in her 80s before she is able to apply for parole.

Last week, her barrister Richard Edney told a hearing in Melbourne that she intended to appeal against her conviction, though this has not yet been formally lodged.

Patterson’s appeal is not an automatic right. Her legal team must convince the appeal court in the state of Victoria that there were legal errors and that it should hear the appeal. No details have been given on their grounds for appeal.

The intense public interest in her case created a media frenzy and saw journalists, podcasters and documentary makers from around the world – as well as members of the general public – descend on the small courthouse in the country town of Morwell.

Patterson killed her in-laws Don and Gail Patterson, both 70, and Gail’s sister Heather Wilkinson, 66, after serving them individual portions of beef Wellington containing death cap mushrooms at her home in Victoria in 2023.

Heather’s husband, Ian Wilkinson, a local pastor, survived the lunch after weeks in hospital and still has ongoing health issues related to the poisoning.

Patterson’s estranged husband, Simon Patterson, was meant to attend the lunch but cancelled at the last minute, in part due to his belief that his wife had been trying to poison him for years.

Following the trial, it was revealed that he had become so violently ill after eating several of her meals in the past that he had been in a coma, a large part of his bowel had been surgically removed, and his family were told to say goodbye to him twice as he was not expected to survive his ailments.

During sentencing, Justice Christopher Beale agreed that Patterson’s crimes were the worst of their kind, but said his decision to allow parole was influenced by the “harsh prison conditions” she faced.

He noted that she had spent 15 months in solitary confinement at the time of her sentencing, and, for her own safety, there was a “substantial chance” that she could face more time in an isolation wing, where prisoners are not allowed to mix and meals are delivered via a small opening in the cell door.

The judge noted that Patterson’s reputation and the high level of media and public interest in the case meant she would likely “remain a notorious prisoner for many years to come, and, as such, remain at significant risk from other prisoners”.

Justice Beale further described Patterson’s current jail conditions in a female maximum security prison – the Dame Phyllis Frost Centre in Melbourne – where she spends 22 hours a day in her cell with no contact with other inmates due to her “major offender status”.