Prosecutors have lodged an appeal against mushroom killer Erin Patterson’s sentence on the grounds the judge “erred” when he considered the triple murderer’s time in solitary confinement.

Patterson was handed three life sentences for the murders of Heather Wilkinson, Don Patterson and Gail Patterson, and 25 years for the attempted murder of Ian Wilkinson, with a 33-year non-parole period.

Prosecutors have lodged an appeal on the basis there was an error in the sentence imposed and that it was “manifestly inadequate”.

“The sentencing judge erred in finding that there was a ‘substantial chance’ the respondent would be held in ‘solitary confinement for years to come’ when such a finding was not open on the evidence, and that finding infected his assessment of the respondent’s likely future conditions in custody and his decision to fix a non-parole period,” the appeal filing notes.

The filing also stated it was inappropriate for the judge to fix a non-parole period.

Patterson is also expected to appeal her convictions.

The 51-year-old’s appeal period was due to expire at 11.59pm today, but during the hearing last Thursday, Justice Christopher Beale cited a new court practice note directing applications for appeal extensions of 28 days or fewer to be granted automatically.

Patterson’s defence had not given any indication of an intention to appeal during her sentencing last month.

To appeal her sentence or convictions, Patterson’s defence team need to provide specific grounds for the appeal, such as errors of law, an unreasonable verdict, or a miscarriage of justice.

If the appeal grounds are valid, Patterson’s case would be heard by judges in the Court of Appeal.

These judges have the ability to overturn sentences or convictions if they find grounds to.

If an appeal against a sentence is allowed, the Court of Appeal could reduce or increase the sentence.

If the Court of Appeal decides there was no legal error, the appeal will be dismissed and the original sentence will stand.

A breakdown of Patterson’s prison sentence

Patterson was last month sentenced to life in prison with a non-parole period of 33 years, meaning she will remain behind bars for at least that long.

Assuming it is not successfully appealed, Patterson’s sentence, which includes the 676 days she served in pre-sentence detention, would see her eligible for release on parole in 2056 at the age of 81.

Beale sentenced Patterson to four separate sentences, all to be served concurrently: