Former Sydney teacher Chris Dawson is now awaiting a verdict after the conclusion of his lengthy murder trial, with the judge indicating he hopes to deliver a decision "relatively quickly".
Mr Dawson, 73, pleaded not guilty to murdering his first wife, Lynette Dawson, who vanished from the city's northern beaches in January 1982.
The Crown alleged Mr Dawson's motivation was to have an "unfettered relationship" with the family's teenage babysitter, known in court as JC, who was also a student at the high school where he taught.
The NSW Supreme Court heard the former rugby league player was "besotted" with the teenager, who he later married, and came to view his wife as an "impediment" to being with JC.
Mr Dawson's defence team argued it was possible Ms Dawson made the decision to abandon her family, having seen the "writing on the wall" that their relationship would not recover from a breach of trust.
On her fifth and final day of a closing address, his barrister Pauline David told the court Ms Dawson would have been "understandably, deeply hurt" by her husband's behaviour with JC.
She argued it was a contributor to Ms Dawson's decision to leave the home.
"We say notwithstanding his relationship, however inappropriate, the defence position is that doesn't make him a murderer," Ms David said.
Mr Dawson has maintained he dropped his wife off at a bus stop in Mona Vale on January 9, 1982, and planned to meet up with her later at a pool with their children.
While he didn't give evidence during the trial, he has claimed to police that Ms Dawson called him at the pool and told him she needed time away to think about things.
He further claimed to have received similar phone calls in subsequent weeks.
Mr Dawson's defence team relied on those calls, a suggestion Ms Dawson's bank card was used shortly after her disappearance, and alleged sightings of her by five people between 1982 and 1984, to suggest she could have been alive after January 1982.
Ms David told the judge that was a reasonable hypothesis which had not been excluded by the Crown.
"I hope to be able to provide my judgement relatively quickly," Justice Ian Harrison said at the conclusion of the submissions.
"That doesn't mean tomorrow, I can assure you."
The Crown did not oppose the continuation of Mr Dawson's conditional bail.
