Horrific details of the relationship between a teenage babysitter and Chris Dawson emerged throughout his murder trial, with the woman claiming the older man treated her as a "sex slave".

Dawson was taken to jail after sensationally being found guilty of the 1982 murder of his first wife, Lynette Dawson.

Justice Ian Harrison found that the 74-year-old was "infatuated" and "obsessed" with his former teenage babysitter, referred to as JC.

He found Dawson had "resolved to kill his wife" so he could finally be with his student, with whom he had formed a sexual relationship while Lyn was still alive.

"I am satisfied that distressed, frustrated and ultimately overwhelmed and tortured by her absence up north, Dawson resolved to kill his wife," he said.

JC provided an unsettling insight into their relationship throughout the trial, with Justice Harrison saying Dawson's obsession with the 16-year-old started when he was teaching her at a school on Sydney's northern beaches.

JC met Dawson in 1980 when he was her Year 11 physical education teacher and she was soon asked to be the babysitter for the two children he shared with Lyn.

She moved into the couple's home in late 1981, with JC claiming she would have sex with Dawson while his wife was asleep.

The teen was forced to move out of the family's home when Lyn confronted her over the situation, accusing her of "taking liberties" with her husband.

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Chris Dawson was found guilty of murdering his wife Lynette decades ago. Photo / Getty Images

Days before Christmas in 1981, JC and Dawson packed up a car with plans of running away to Queensland together.

However, before they reached the border, JC became ill and said she wanted to return to Sydney, with the pair arriving back on Christmas Day.

In early 1982, the teenager went to South West Rocks on NSW's Mid North Coast on a holiday with her family and friends and phoned Dawson every day.

JC said during one phone call Dawson told her: "Lyn's gone, she's not coming back, come back to Sydney to help me look after the children."

She moved back into the Bayview home and began sleeping in Dawson's bed and wearing his wife's clothes.

'I was a child'

During the trial, JC hit back at the suggestion that she had a "relationship" with the older man.

"It wasn't a relationship. I object to that … I was a child!" she told the court.

She claimed Dawson treated her like his "slave".

"I was taking care of two children, having to learn to cook, having to learn to clean … having to learn how to be a substitute housekeeper, sex slave, stepmother, babysitter … slave … just a slave," she said.

The pair married in 1984 and moved to the Gold Coast in Queensland.

Chris Dawson and JC on their wedding day in 1984. Photo / Supplied, File

JC told the court of an incident on their wedding night when she said Dawson grabbed her around the throat, describing it as "frightening".

In 1985, JC gave birth to their first and only child. It was after the birth that JC claims Dawson underwent an "enormous" change.

She said he was frustrated with her inability to emotionally connect with his two other daughters and the fact that she had a stronger bond with her own daughter.

This was when the woman claims she started to see an even more violent side of Dawson.

"I feared for my life by that time," she told the court.

JC described feeling isolated living on their 7.5 acre (3ha) property at Yawalpah and recalled an incident where Dawson became physical with her after she had squirrelled away and bought a G-string.

"He got physically violent at me and said, 'You're not going to wear that for anybody but me,'" JC told the court.

" 'You don't have any rights' kind of thing. And he ripped them off me."

'You could easily get rid of me'

JC told the court she was in a "domestic violence situation" and it was "daily, all the time".

As the situation continued to deteriorate, she recalled telling Dawson: "You got rid of your first wife, you could easily get rid of me."

"He stood completely still … and said 'don't say things like that'," she said.

The pair eventually divorced in 1990, with JC winning custody of their daughter.

During the cross-examination, barrister Pauline David argued JC held genuine affection for Dawson during the "early stage of the 1980s".

"In the grooming stage, you mean?" JC responded.

David accused JC of making up the domestic violence allegations, including that he had put his hands around her neck on their wedding night.

"It's a part of your absolute determination to destroy Christopher Dawson," David said.

"I'm not going to destroy him, he will destroy himself for what he's done to people – to me, to Lyn. I'm telling the truth," JC replied.

In the wake of the guilty verdict, Lyn's family have expressed gratitude to JC, saying she played a "pivotal role" in Dawson's murder conviction.

Chris Dawson and Lynette Dawson from a Simms family photo album tendered to the NSW Supreme Court. Photo / Supplied, File

Speaking on the Today show, Lyn's niece Renee Simms spoke highly of the then teenage "victim".

"We have always thought that she's a victim in this too," Simms said.

"We are so incredibly grateful that she had the courage and the willingness to come forward because she played a pivotal role in getting us a verdict that we got yesterday.

"So we're incredibly grateful and we absolutely do not blame her at all for any of this."

JC was a central component of the Crown's case that Dawson had the motive to kill his wife.

- Ally Foster, news.com.au