The first witness will give evidence as the trial over a poisonous lunch cooked by alleged triple murderer Erin Patterson continues.

The 50-year-old mother, who has pleaded not guilty to three murder charges and one of attempted murder, faced the first full day of her jury trial in regional Victoria on Wednesday.

Prosecutors claimed Patterson told a series of lies before and after the fatal lunch at her home in Leongatha on July 29, 2023.

These included false claims she had cancer, lies to police about disposing of a dehydrator and that she did not go foraging for mushrooms.

Prosecutors also alleged she feigned illness after eating her portion of the lunch.

Defence barrister Colin Mandy SC said Patterson accepted some of the claims she lied about, but denied that she had not told the truth about becoming sick after lunch.

He claimed she told some lies because she had "panicked" after her guests became ill from her cooking amid intense police and media scrutiny.

He told the 15 jurors Patterson had no intention to kill or cause "any harm" to any of her guests.

Following Sunday service at Korumburra Baptist church on July 16, Patterson invited her estranged husband, Simon, his parents, Don and Gail, and his aunt and uncle, Heather and Ian Wilkinson, to lunch at her home.

Simon declined, but the rest of his family attended a meal that would become deadly.

She served beef Wellington to her guests, which consisted of steak covered in a paste containing death cap mushrooms wrapped in pastry.

Prosecutor Nanette Rogers SC claimed that Patterson served the meals to her guests on plates different from hers.

Evidence will begin on Thursday, and the first witness is expected to be called at the Latrobe Valley Courts in Morwell at 10.30 am as the trial continues.

With AAP.