This includes the person's age, weight, their tolerance to the mushroom's poison and the amount that they consume, toxicologist Dimitri Gerostamoulos told a Supreme Court jury in regional Victoria on Friday.
Patterson, 50, has reached the mid-way point of a trial where she is accused of murdering three of her estranged husband's family members by deliberately poisoning them with a beef Wellington.
She has pleaded not guilty to three counts of murder and one of attempted murder over the July 2023 meal which led to the deaths of Don and Gail Patterson, 70, and Heather Wilkinson, 66, and hospitalisation of Heather's husband Ian.
Patterson claims the deaths were all a terrible accident.
She took herself to hospital two days after the lunch and claimed she had eaten the same meal as her in-laws but was found to be well enough to be discharged by doctors on August 1.
A child protection worker on Thursday said Patterson told her she'd eaten half of her serve of the beef Wellington, and complained of feeling unwell and experiencing loose bowel movements.
Defence barrister Colin Mandy SC on Friday cross-examined Dr Gerostamoulos, the Victorian Institute of Forensic Medicine's chief toxicologist.
He asked whether some individuals could be "less severely affected than others" after consuming death cap mushrooms because of the amount they had ingested.
"Yes that's possible," Dr Gerostamoulos said.
"The age of the individual might be a factor?" Dr Mandy continued.
"That can be a factor," he replied.
Dr Gerostamoulos also agreed that the weight of the person may be a factor, as could the individual's tolerance to the toxin.
Prosecutor Sarah Lenthall then re-examined the toxicologist.
"If two adults with no serious pre-existing health conditions consumed the same amount of the same meal, which contained death cap mushrooms, and one person dies - what are the health outcomes for the person who did not die?" she asked.
"There likely would be adverse outcomes for the person who survived, the severity of which may vary," Dr Gerostamoulos replied.
More photos of the poisoned beef Wellington were shown to the jury on Friday, as Plant Health Victoria diagnostics manager David Lovelock gave evidence.
He performed a second test on remains of the meal and found no sign of death cap mushrooms.
Dr Lovelock said he did find death cap mushrooms inside a food dehydrator, which had been seized by police from a tip days after the meal.
Another scientist, Camille Truong, also found no sign of death caps in the meal when examining it under a microscope.
However, Dr Gerostamoulos told the jury on Thursday he found death cap mushroom toxins inside the meal's remains when he performed chemical testing.
Justice Christopher Beale sent the jury home for the weekend with a warning after one of their fellow jurors was dismissed for discussing the case with family and friends.
"I don't want to sound like a broken record but only discuss the case with your fellow jurors in the privacy of the jury room," he said.
The trial will resume on Monday.
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