Chris Dawson had lost the chance to gather records and eyewitness testimony proving his wife was still alive because he went on trial for her murder 40 years after she disappeared, a court has been told.
The ex-PE teacher is appealing against an August 2022 verdict by Justice Ian Harrison that he killed his wife Lynette Dawson and disposed of her body on January 9, 1982 because he was infatuated with a teenage student.
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 her client suffered a significant forensic disadvantage because of the length of time it had taken to prosecute the case.
The appeal revolves around a critical phone call Dawson claims he received from his wife while at Northbridge Baths in Sydney's Lower North Shore on January 9, 1982.
In that call, he says Ms Dawson wanted to take a few days away from her family.
At the time, her husband had become infatuated with the teen student, trying to abandon his family over Christmas 1981 and start a new life with the girl in Queensland.
Justice Harrison found Ms Dawson was dead by January 1982 and that the claimed phone call was a lie by the ex-teacher to cover up what he had done.
Ms Rigg told a three-judge panel on Monday that because of the delay, her client had been unable to source critical phone records and bank statements to try and prove his wife was still alive.
He was also unable to get original police statements and cross-examine certain individuals who claimed they had seen Ms Dawson after she disappeared, the barrister argued.
"The quality of the evidence is greatly impoverished," she told the court.
Ms Rigg argued her client did not kill his wife, instead making an effort to repair their relationship in the days before she disappeared.
This was because the teenage student, who can legally only be identified as JC, had indicated she did not want to be in an intimate relationship with her teacher, Ms Rigg said.
"The evidence indicates that (Dawson) in January 1982 had feelings for both women, for JC and for his wife," she said.
Ms Rigg said it was plausible Ms Dawson had decided to take a few days alone as her client had claimed.
"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 Ms Dawson was not alive on January 9, 1982, the court was told.
"He contends that on the whole of the evidence, it was not open to be satisfied beyond reasonable doubt of his guilt," Ms Rigg said.
While Ms Rigg admitted her client had been in love with the teenage girl at the time his wife disappeared, she said there was no evidence he was jealous or possessive of her at the time.
A key finding by Justice Harrison was that Dawson killed his wife because he was infatuated with the babysitter.
If Dawson's legal challenge fails, the former Newtown Jets rugby league player is likely to die in jail after being sentenced to a maximum prison term of 24 years.
The jail stint will expire in August 2046 - when he would be aged in his mid-90s.
He will be able to apply for parole in August 2041 after his non-parole period was extended by a year when he was found guilty of unlawful carnal knowledge with the same then-underage student.
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 the full-term.
The hearing continues on Tuesday.
1800 RESPECT (1800 737 732)
Lifeline 13 11 14
