An Australian woman accused of murdering three of her estranged husband's elderly relatives with poisonous mushrooms gave her account of the fatal lunch on Wednesday, in a case that has gripped the public.

Erin Patterson, 50, is charged with the July 2023 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 prosecution alleges she knowingly served the guests lethal death cap mushrooms in a beef Wellington at her home in Leongatha, a town of around 6,000 people some 135 kilometres from Melbourne.

She denies the charges, with her defence saying the deaths were a "terrible accident." She faces a life sentence if found guilty.

The accused, the first witness for her own defence and who began her evidence on Monday afternoon, repeatedly wept as she told the court on Wednesday she may have accidentally included foraged mushrooms into the food she served.

"Now I think there was a possibility there were foraged ones in there," she said as she was questioned by her own barrister, Colin Mandy.

The court also heard on Wednesday that Erin Patterson had invented medical issues partly to elicit sympathy from her estranged husband's relatives, from whom she said she felt she was growing apart.

"I didn't want their care of me to stop, so I kept it going. I shouldn't have done it," she told the court.

"Did you lie to them?" Mandy asked.

"I did lie to them," the accused replied, through tears.

The prosecution alleges Patterson invented the medical issues to lure the victims to her home for the meal, a claim she denies.

The prosecution rested its case on Monday, following a month of evidence from witnesses, including relatives and medical, forensic and mushroom experts.

The trial, which began on April 29, has seen intense interest from Australian and international media, with podcasters, journalists and documentary-makers descending on the town of Morwell, around 155 kilometres east of Melbourne, where the trial is being held.

State broadcaster ABC's daily podcast about proceedings is currently the most popular in the country, while many Australian newspapers have been running live blogs on the case.

The trial, scheduled to conclude this month, continues.