A finding that Chris Dawson murdered his wife was unreasonable because he had loved her and tried to restore a relationship fractured as he pursued a teenage girl, a court has been told.

The ex-teacher is appealing against a verdict by Justice Ian Harrison from August 2022 that he murdered his wife Lynette and disposed of her body on January 9, 1982 because he was infatuated with the schoolgirl.

As a three-day hearing started in the NSW Court of Criminal Appeal on Monday, the 75-year-old’s barrister, Belinda Rigg SC, said Dawson made an effort to repair the relationship with his wife in the days before she disappeared.

This was because the teenage student, who can legally be identified only as JC, had indicated she did not want to be in an intimate relationship with her teacher, Rigg said.

“The evidence indicates that [Dawson] in January 1982 had feelings for both women, for JC and for his wife,” she said.

Dawson and his wife had attended marriage counselling on January 8, 1982, and were seen as being positive and happy.

However, he had told police Lynette appeared distressed that night while drinking wine. She disappeared the next day.

Rigg said it was plausible Mrs Dawson had decided to take a few days alone to think things over given her husband’s pursuit of his student and babysitter.

“She and [Dawson] were at an absolute crossroads in terms of working out what to do,” the barrister said.

“Her circumstances were likely to have been equally fragile at the time.”

Dawson watched the hearing by video-link from Clarence Correctional Centre near Grafton.

There was not enough evidence to show his wife was not alive on January 9, 1982, when Dawson claimed he received a phone call from her at a swimming pool on Sydney’s lower north shore, a three-judge panel was told.

Dawson said of that conversation that his wife had told him she needed time alone.

“He contends that on the whole of the evidence, it was not open to be satisfied beyond reasonable doubt of his guilt,” Rigg said.

To prove Dawson guilty of murder, crown prosecutors needed to show that his wife was dead by the time of the Northbridge Baths phone call, she said.

While Rigg admitted her client had been in love with the teenage girl at the time his wife disappeared, she said there was no evidence that he was jealous or possessive of her at the time.

A key finding by Harrison was that Dawson killed his wife because he was infatuated with the babysitter.

If Dawson’s legal challenge fails, the former PE teacher and Newtown Jets rugby league player is likely to die in jail after being sentenced to a maximum prison term of 24 years.

His term will expire in August 2046 – when he would be in his mid-90s.

His sentence was extended by a year when he was found guilty of unlawful carnal knowledge with the same then-underage student, and he will not be able to apply for parole until August 2041.

Because Lynette Dawson’s body has never been found, laws preventing convicted murderers from being paroled until they disclose the location of their victims mean Dawson could be forced to serve his full term.

The hearing continues.