A juror has been dismissed from Erin Patterson's triple murder trial after a judge was told they discussed the case with family and friends.
Justice Christopher Beale discharged one of 15 jurors, who cannot be identified for legal reasons, from the court in regional Victoria on Thursday.
"I received information that (the juror) had been discussing the case with family and friends, contrary to my instructions," he told the jury.
"I was of the view that there was at least a reasonable possibility the information I received was credible."
He said he had not made a "positive finding" that the juror had discussed the case outside the jury room, but he could not dismiss that as a possibility.
"It was at least a possibility that he had breached my instructions," the judge said.
The judge told jurors not to contact the discharged juror.
He also issued a warning to the 14 remaining jurors, who will be whittled down to 12 to decide Patterson's fate at the end of the trial, to discuss the case only among themselves.
Erin Patterson's trial in Morwell, about two hours' drive from Melbourne, is nearing the end of its third week.
She has pleaded not guilty to three counts of murder and one of attempted murder over a poisonous beef Wellington she served to her former in-laws Don and Gail Patterson, Heather and Ian Wilkinson.
Wilkinson was the only guest to survive the July 2023 lunch.
Victorian Institute of Forensic Medicine chief toxicologist Dimitri Gerostamoulos gave evidence about his testing of the poisonous meal.
He confirmed that beta-amanitin, the toxic compound found in wild mushrooms, had been detected in the mushroom paste and the meat remains he tested.
It comes after scientist Camille Truong on Wednesday said she had done a microscopic test of the beef Wellington leftovers and found no signs of death cap mushrooms.
Additionally, Dr Gerostamoulos found evidence of the deadly toxins inside a food dehydrator police seized from a tip in the days after the meal.
He tested blood and urine samples from the four lunch guests, as well as Erin Patterson and said nine samples from Patterson were analysed but no toxic compounds found.
