Former Sydney teacher Chris Dawson allegedly used an "engineered window of quiet seclusion" to dispose of his murdered wife's body after four separate plans to leave her failed, a judge has been told.
The former rugby league player, 73, has pleaded not guilty to murdering Lynette Dawson, who hasn't been seen since early 1982.
In a closing address, Crown Prosecutor Craig Everson SC told the NSW Supreme Court Mr Dawson was "besotted" and "infatuated" with their babysitter — a student at the high school where he taught known as JC.
By late 1981, Mr Dawson was "desperate to do whatever he needed to do to pursue that relationship and secure what it was he desired in her," the court heard.
Mr Everson described four "plans" he said Mr Dawson had to end the relationship with Ms Dawson and instead pursue JC, to whom he had proposed marriage.
They included searching for a flat in Manly, unsuccessfully attempting to get Ms Dawson to sign paperwork to sell their northern beaches house and allegedly contemplating the recruitment of a hitman.
Mr Everson said the final, short-lived plan was for the pair to move to Queensland around Christmas 1981, but the court has heard they returned before reaching their destination because JC was sick and wanted to return to her family.
By this point, he argued, Mr Dawson's "slide into moral turpitude was obvious to those who knew what he was doing".
Mr Everson said the potential loss of JC caused him considerable anxiety and he came to view his wife as an "impediment" to being with her.
"His obsession with JC, his fear of losing her and the impediment his wife posed ... ultimately motivated him to murder her," Mr Everson said.
Mr Dawson has maintained Ms Dawson called him while he was working as a lifeguard at the Northbridge Baths one day in January 1982 to tell him she wouldn't be returning home.
Mr Everson told Justice Ian Harrison that by January 9, 1982, Mr Dawson "had his dominoes all lined up and they were ready to fall".
He said Mr Dawson didn't say anything to anyone about what he was doing that night, and no person has given evidence about seeing him.
"The Crown contends that this engineered window of quiet seclusion gave the accused the opportunity to dispose of a body before he started making his way north to collect JC."
Mr Dawson's legal team has challenged the hitman allegation by highlighting its timing; it was first disclosed by JC during acrimonious family law proceedings in 1990.
But Mr Everson said the timing of the allegation should be looked at "in a broader context" that extended years prior.
Mr Dawson's barrister, Pauline David, began her own closing address by acknowledging he may have "failed" his wife but said he did not have any motive to get rid of Lynette Dawson.
She said the case had a 30-year history of investigation, but both the investigation and media reporting had been to the effect that Mr Dawson was "a guilty man".
"He has not ever been afforded the presumption of innocence," Ms David told the judge.
She said what was "more frightening" was the "significant forensic disadvantage" the accused now experienced, because of a "coloured prism" through which the case had been viewed since the late '90s.
"Everything he has said has been discounted or ignored ... his voice has been completely quashed."
Ms David said Lynette Dawson may have concluded the relationship was "not going to work" and left.
"That is not unusual in the sense that her trust had been breached horribly by Christopher Dawson," she said.
"Perhaps she saw the writing on the wall that the relationship was not going to recover."
