Court of Appeal orders retrial for alleged arsonist Shilane May Quist after juror asked their mum what she thought

A woman who was found guilty of firebombing a strip mall has had her conviction quashed because a juror broke the rules.

A woman found guilty of a shopping centre arson attack has won a retrial on appeal after a juror discussed the case with their mum.

Shilane May Quist, 66, was found guilty at trial in March this year of the blaze in a toilet at Parafield Gardens Shopping Centre in December 2013.

But her conviction was quashed by the Court of Appeal on Thursday.

Shilane Quist won a retrial on allegations she firebombed a strip mall to get an insurance payout on her mother's newsagency. Picture: Greg Higgs

She had yet to be sentenced.

The appeal judgment reveals a juror in the District Court trial had discussed the case with their mother after the jury had begun its deliberations. Asked for her thoughts, the mother had advised the juror “you can’t find her guilty”.

The jurors had been allowed home overnight on the understanding there was “no discussion or communication with anyone else about the issue or the case whatsoever”.

The next morning, trial Judge Liesl Chapman was alerted to the juror’s discussion with their mum by a note from the jury.

She declined to declare a mistrial, later telling defence counsel she had refused because she was “anticipating a real chance of acquittal”.

In the unanimous judgment, president Trish Kelly, and Justices Mark Livesey and Chris Bleby, said Judge Chapman’s failure to declare a mistrial “caused a miscarriage of justice” and an “interference with the integrity of the functions of a jury”.

They set aside the conviction and ordered a retrial.