A “generally truthful” woman groomed by Chris Dawson as a teen might be wrong about a crucial element holding up the wife-killer’s other criminal conviction, judges have heard.

The 76-year-old has appealed a conviction related to sexual abuse of a former student who later moved into his home.

His total sentence for that offence was mostly subsumed into his full 24-year sentence for murdering his wife Lynette Dawson in January 1982, adding one year to his non-parole period.

While he had admitted sexual intercourse with the teen in Sydney’s eastern suburbs, he denied this happened until after her 17th birthday – a critical element of the offence.

His challenge of the carnal knowledge verdict was heard in the NSW Court of Criminal Appeal today where barrister Stephen Odgers SC said there were plenty of questions surrounding evidence from the complainant, known in the case as AB.

He argued there were real questions around exactly when Dawson and AB had their first kiss during driving lessons, and when he and his twin brother Paul gave fitness classes to her and another teenage girl.

AB contends the first act of sexual intercourse took place after both the kiss and the fitness classes, anchoring it to the year before her 17th birthday.

But Odgers said the court should acquit Dawson if satisfied there were enough questions around the timing of the first act of sexual intercourse.

“Even if the judge correctly finds she’s generally truthful, generally reliable, there still may be reasons for doubt,” Odgers told the court.

Dawson has also challenged the verdict as unreasonable.

He silently watched the hearing from a small room at Silverwater prison in Sydney’s west, speaking only briefly to tell the court that he was OK to continue.

During the District Court trial in 2023, the court was told the then-PE teacher groomed AB during fitness classes and organised a tennis match so the girl could meet his wife and start babysitting.

The teen started sleeping with Dawson and eventually moved into his home soon after Lynette was murdered and he disposed of her body, the NSW Supreme Court found when he was convicted over the killing in 2022.

For the carnal knowledge verdict, while Judge Sarah Huggett acknowledged discrepancies in AB’s evidence, she nonetheless found the 76-year-old guilty.

Crown prosecutor Helen Roberts SC urged the appeals court to uphold the judge’s findings.

She pointed to other “compelling” evidence that showed Dawson was indeed engaged in sexual activity with AB in 1980, as opposed to just showing her romantic affection.

In a birthday card given to the girl on her 17th birthday in 1981, the teacher described her as “the most beautiful girl in the world”.

“To my lovely, beautiful bub,” he wrote.

“Hoping today is a very happy one.”

Other conduct included threats made to a teenage boy who expressed interest in AB, standing between her legs as she sat on his desk at school, and attending a local pub to meet with her and her friends.

This showed there was a physical relationship in 1980, Roberts said.

By the end of 1980, Dawson said he loved AB and wanted to marry her, the court was told.

During fitness classes the following year, there was “kissing and cuddling and canoodling” including in the facility’s swimming pool, Roberts said.

The appeals court’s judgment will be delivered at a later date.

Dawson’s appeal of the murder conviction was thrown out in June.

His 18-year non-parole period for murder expires in 2040.