Ms Dawson's sister Patricia Jenkins on Tuesday testified at the NSW Supreme Court trial of Chris Dawson, who has pleaded not guilty to murdering his wife and mother of their two children in January 1982.
The Crown claims Dawson, 73, a former Newtown Jets rugby league player and teacher, killed his wife and disposed of her body because of his affair with one of his students, known as JC.
Dawson's legal team has argued at the trial that he might have failed his wife as a husband, but he did not kill her.
The court on Tuesday was told Ms Dawson initially appeared to have a happy marriage, but by 1981 there were tensions in the Bayview, Sydney, home about the presence of JC.
It was told tensions eased when Dawson left the family in late 1981 but that Ms Dawson had little money and did not know what the future was going to be.
"She was in great distress, I could tell by her voice," Ms Jenkins said,.
She agreed Ms Dawson was intelligent, made independent decisions and stood up to people, but said "I think she was cowered" by Dawson by 1981.
Quizzed over whether Ms Dawson could have needed a break from what was going on in the household, her sister conceded it was a remote possibility.
"There's always that little bit of hope you're going to find her," she said.
Ms Jenkins in her evidence became emotional, but declined a break in proceedings, when recalling a conversation with her sister a day or two before Christmas 1981 in which she was told that Dawson had left the family.
The witness said Ms Dawson told her she came home to find a note on the bed from Dawson that said: "Don't paint too dark a picture of me to the girls".
She said her sister told her Dawson's clothes and pillow were gone and that "she didn't know if Chris was coming home again or not", causing her to be upset.
She also testified her sister told her she was worried about Dawson's health due to him being angry at her, and thought there may be a physical cause.
Ms Jenkins said she spoke of her husband's "black eyes flashing", trying to give him a hug but being pushed away, and him giving her "such a dirty look".
The last time Ms Jenkins talked to her sister was on New Year's Day 1982 when Ms Dawson told her of a "sad Christmas" and a yacht party that Dawson attended.
"I've not seen her since then, not heard from her since then," Ms Jenkins said.
She described listening to the The Teacher's Pet podcast as "very overwhelming" and conceded meeting with its creator Hedley Thomas.
Also on Tuesday, Ms Dawson's brother Greg Simms gave evidence, describing Dawson, who was best man at his wedding, as a "very colourful character".
He agreed his sister was very stressed in late 1981 about the state of the relationship with Dawson whom she loved "with all her heart", and recalled Dawson saying of his sister that year: "She can get in the bloody kitchen where she belongs".
He denied making up evidence about a sales inspection report he said he found in a blue dressing gown owned by his sister to "convey Mr Dawson in a poor light".
"No, that's incorrect," Mr Simms said.
The judge-alone trial continues on Wednesday.
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