Dawson 'noticed' student after seeing topless photo

Convicted wife-killer Chris Dawson's first interaction with a student he's accused of having an unlawful sexual relationship with was to return a topless photo.

Taken on a picnic when the student, known in court only as AB, was 14 or 15, the photo was circulating around her school where he taught.

Before he saw a picture of her in a "vulnerable position", she "went unnoticed" by Dawson and had little to do with him.

"There was no need, he wasn't my teacher. I was ensconced in my social group and trying to navigate that normal 15-year-old life," she told the NSW District Court on Tuesday.

Dawson, 74, has pleaded not guilty to engaging in sexual activity with AB between July and December 1980 while she was aged 16 and his student on Sydney's northern beaches.

The historical carnal knowledge charge, which Dawson denies, was replaced in 1986.

Prosecutors have to prove the alleged sexual activity occurred while he was her teacher, public defender Claire Wasley said.

Crown prosecutor Emma Blizard said it is not disputed sexual activity took place.

"The central issue will be one of timing and when events commenced," Ms Blizard said.

Dawson said he wanted AB in his class to get to know her, telling her that numerous times.

"Because it softened me," she said, giving evidence on Tuesday.

He made her feel special and she began confiding difficulties she was having at home, before he allegedly put his hand on her bare knee at a sports carnival.

She started babysitting Dawson's children, almost every weekend, including while he and his wife spent the night at home.

He began attending the pub where AB and other students drank underage on Fridays, telling her stories about "how fabulous he was" as "part of the grooming process".

"It just got out of control in terms of the amount of time I was spending with him," she said.

She was brought to exercise classes Dawson taught with his twin brother.

"When one twin was running the class the other was out the back with whichever student was their property at the time," AB said.

Ms Wasley reminded Judge Sarah Huggett she is not required to judge Dawson by contemporary legal or moral standards and what she knows about his conviction for murder should have no bearing.

She said it was disputed the alleged sexual activity started while AB was Dawson's student.

AB told the court she was 16 and Dawson was her teacher when the first alleged sexual activity occurred at his parents' home at Maroubra in Sydney's south.

He told her to keep it a secret, AB said, and it continued, at Dawson's home, in his office at the school, and in the back of his car once he removed the baby seat.

He left notes in her bag while she sat in classes and left coded messages on her school reports, noting in November 1980 she was a "pleasure to teach".

"He wasn't referring to teaching sports coaching ... he thought it was very clever to be able to put that on a public document," she said.

Dawson was jailed in 2022 for murdering his wife Lynette in January 1982, with a judge finding he was motivated by a desire to pursue an unfettered relationship with a student.

Health issues in his old age mean Dawson will have frequent breaks during the judge-alone trial.

His lawyers observed Dawson having difficulties following the proceedings and he will appear via audiovisual link rather than being ferried to and from prison to attend court from Wednesday.

1800 RESPECT (1800 737 732)

National Sexual Abuse and Redress Support Service 1800 211 028