Australian woman found guilty of murder after serving poisonous mushrooms to in-laws for lunch

An Australian woman was on Monday convicted of murdering three elderly relatives of her estranged husband with a meal laced with poisonous mushrooms, in a case that has gripped the country.

Erin Patterson, 50, was charged with the murders of her mother-in-law Gail Patterson, father-in-law Donald Patterson and Gail's sister, Heather Wilkinson, along with the attempted murder of Ian Wilkinson, Heather's husband.

The four gathered at Erin Patterson's home in Leongatha, a town of about 6,000 people some 135 kilometres southeast of Melbourne, where the mother of two served them a meal of individual Beef Wellingtons accompanied by mashed potato and green beans, which were later found to contain death cap mushrooms.

On Monday, the jury in the case found her guilty of all four charges, the court heard in Morwell, a town around two hours east of Melbourne where the trial was being held.

Her barrister, Colin Mandy, made no comment as he left the court through a scrum of journalists.

Jessica O'Donnell, a spokesperson for Patterson's estranged husband, Simon Patterson and his siblings, also declined to comment.

Patterson, who had pleaded not guilty to all charges, saying the deaths were accidental, will be sentenced at a later date.

The 10-week trial attracted huge global interest, with local and international media descending on Court 4 at the Latrobe Valley Magistrates' Court in Morwell, the nearest court to Patterson's home where she had requested to be tried, despite being warned of lengthy delays.

State broadcaster ABC's daily podcast on proceedings was consistently among the most popular in Australia during the trial, while several documentaries on the case are already in production.

The prosecution, led by barrister Nanette Rogers, told the court that Patterson had employed four major deceptions in order to murder her guests.

She first fabricated a cancer diagnosis to lure the guests to the lunch, poisoning their meals while serving herself an untainted portion, Rogers told the court.

Patterson then lied that she was also sick from the food to avoid suspicion, before finally embarking on a cover-up when police began investigating the deaths, attempting to destroy evidence and lying to police, the prosecution said.

Patterson, who said during the trial she had inherited large sums of money from her mother and grandmother, retained a four-person legal team, led by Colin Mandy, one of Melbourne's top criminal barristers.

She was the only witness in her defence, spending eight days on the stand, including five days of cross-examination.

Patterson told the court about a life-long struggle with her weight, an eating disorder and low self-esteem, frequently becoming emotional as she spoke about the impact of the lunch on the Patterson family and her two children.

She had lied about having cancer not to lure the guests to the lunch to kill them, but because she was looking for their help with telling her children and was embarrassed to say that she actually planned to have weight loss surgery, she told the court.

Patterson had also not become as sick as her lunch guests because she secretly binged on a cake brought by her mother-in-law and then purged herself, she told the court.

The jury of seven men and five women retired on June 30, taking a week to reach a verdict.

Justice Beale gave the jurors in the trial special dispensation to avoid jury duty for the next 15 years, due to the length and complexity of the case.