Chris Dawson's sister-in-law has told a court the accused murderer was a supportive partner and "hands-on father" who was never violent in her presence.
Marilyn Dawson has been married to Chris' identical twin brother, Paul, since 1969.
In the 1970s, both couples lived on Gilwinga Drive in the leafy suburb of Bayview on Sydney's northern beaches.
Chris Dawson is on trial for the murder of his first wife, Lynette, who went missing in January 1982.
The Crown is arguing he did it pursue an "unfettered relationship" with a 16-year-old student at the high school where he was a teacher.
The student, known as JC, also worked as a babysitter for his family at the time.
Chris Dawson has always denied any involvement in Lynette's disappearance and says she left their home of her own accord.
Today, Marilyn told the court she had never seen Lynette with a black eye or bruised throat, but that she bruised easily in other places.
"Lyn wasn't very muscly, and so she had softer skin, often on her leg or arms there'd be a bruise, and that's just how her body was."
Previous witnesses, including some of Lynette's former colleagues, said they saw bruises on her arms, legs, throat and face in the weeks leading up to her disappearance.
"He was never violent towards Lyn in my presence ever," Marilyn told the court today.
Last month, JC, who went on to become Chris' second wife in 1984, testified that he had arranged for Marilyn to forge Lynette Dawson's signature on life-insurance paperwork after she disappeared.
In a 1999 police interview, Marilyn admitted it was possible she had signed a document, but in the witness box she denied it.
"How many times, if ever, has Chris Dawson asked you to sign something?" Crown prosecutor Craig Everson SC asked today in court.
"Never," she responded.
She said in the final months of 1981, when JC was living with Chris and Lynette Dawson, she believed the marriage had become "shaky".
"I drove Lyn home one day ... I thought she was devastated and maybe mentally she was not coping," she told the hearing today.
"I said 'you need to stay at home because you don't want another person in your home unsupervised' ... I asked Lyn to be strong and stay in her own home if she wanted to show that she loved her children, and her home, and her husband."
She told the court that when Chris Dawson and JC turned up at her home on Christmas morning in 1981, she knew the two were romantically involved but agreed not to say anything to Lynette.
"Chris didn't want Lyn to know he and [JC] were at the house. I know I wasn't happy, but I'm not confrontational ... I felt torn," she said.
She said she hadn't heard from Lynette Dawson since Christmas 1981, and by early 1982 understood Chris Dawson and JC to be "a couple".
