A key prosecution witness in Chris Dawson’s murder trial says she believes he killed his wife and denies shaping her evidence to become an indispensable part of The Teacher’s Pet podcast and any associated movie or television series.

Julie Andrew, a friend and neighbour of mother-of-two Lynette Dawson, has told the NSW Supreme Court she had seen Dawson standing over his crying wife, screaming at her and shaking her shoulders in the backyard of their Bayview, Sydney, home in late 1981 – weeks before she disappeared.

Ms Andrew said she later checked on Ms Dawson who was upset because the babysitter, JC, was going to live at the family home permanently.

Ms Andrew told Ms Dawson she couldn’t let JC, a student at the school where Dawson was teaching, live in her house because he was having sex with the girl.

“It’s your house, you can’t let her move in. He’s f***ing the babysitter,” Ms Andrew said she told her friend.

Having first noticed JC around the house in late 1980, Ms Andrew described her as a “vulnerable teenager” who was often topless at the pool.

“I do believe Chris Dawson murdered his wife,” Ms Andrew said on Monday after being called as the trial’s first witness.

“I’d be lying to you if I said otherwise.”

Questioned by defence barrister Pauline David, Ms Andrew agreed she had no presumption of innocence when it came to Dawson but claimed she was capable of putting any prejudice aside when giving her evidence.

Audio recordings of conversations between Ms Andrew and The Teacher’s Pet podcast creator Hedley Thomas were played to the court where they talked about interest in the case from Hollywood stars such as Hugh Jackman and Joel Edgerton.

Ms David accused Ms Andrew of happily shaping her evidence during Dawson’s trial to ensure the outcome she wanted was achieved. Ms Andrew denied this.

Ms Andrew also rejected claims she had embellished her evidence after getting carried away by her involvement in the podcast and feelings of self-importance.

Asked earlier by crown prosecutor Craig Everson SC what Ms Dawson said when Ms Andrew told her that her husband was having sex with JC, Ms Andrew replied: “She accepted what I was saying was true.

“She’d known it.

“She was deluding herself into thinking things could go back to the way they were between her and Chris.”

Ms Andrew said Ms Dawson had had such a difficult time giving birth to her two daughters that she would never have abandoned them.

She denied claims by Ms David that she had come to court to paint Dawson in the most monstrous way she could.

Dawson, 73,  a former Newtown Jets rugby league player, has pleaded not guilty to murdering his wife in January 1982.

The crown case against Dawson is that he killed his wife and disposed of her body because of his affair with JC.

Ms David, in her opening address to the court on Monday, said Dawson might have failed his wife as a husband, but he did not kill her.

She said the police investigation into Ms Dawson’s disappearance had been flawed and they had failed to follow up alleged phone calls from her and sightings of her after she had supposedly been murdered.

The trial before Justice Ian Harrison resumes on Tuesday.