Former schoolteacher Chris Dawson is a "conniving monster" who betrayed his family, the Hunter-based brother of his murder victim Lynette has told a court.
A statement by Greg Simms, of Lake Macquarie was read out in the NSW Supreme Court, describing how the loss of his sister had impacted generations.
"We considered you an equal in all respects. We trusted you. You repaid us by committing the ultimate betrayal," Mr Simms wrote of Dawson.
Thursday's sentencing hearing comes 10 weeks after Dawson, now 74, was found guilty of murdering his wife in January 1982 so he could have an unfettered relationship with one of his high school students, known as JC.
"It was a brazen act of a conniving monster hell bent on one thing, getting what you wanted at any cost," Mr Simms said.
Wearing prison greens sitting in the court dock, Dawson listened to statements from Mr Simms as well as Lynette's sister Patricia Jenkins and his own daughter Shanelle Dawson.
Before reading her statement, Shanelle took a pause to fiercely stare at Dawson from across the courtroom, breaking into tears before speaking.
"The night you removed our mother from our lives was the night you destroyed our sense of safety and belonging in this world," she said.
She had glimpses of memories from the "nightmare night" her mother disappeared, she said. Her life had been shattered, she found it difficult to trust men, and she had been diagnosed with PTSD after learning what her father was capable of.
"The torture of not knowing what happened, of what you did with her body - please tell us where she is. I hope you will finally admit the truth to yourself," she said.
Ms Jenkins said she had been "confused, alarmed, distressed and in a deep dark void" upon hearing that her sister had disappeared.
Dawson would lie to his daughters after the murder, telling them that Lynette wasn't their "real mother" but was only pretend because she had walked out, Ms Jenkins said.
"Lyn's disappearance and the journey has since taught me that no one is safe from tragedy. It can unexpectedly strike anywhere and justice can also be a long time coming."
Mrs Dawson went missing from the couple's Bayview home in Sydney's northern beaches. Her body has never been found despite extensive police searches.
Also on Thursday, crown prosecutor Craig Everson SC said Dawson had planned a "deliberate and conscious act" of domestic violence with an intention to kill.
He said a crime of "very great heinousness" required a term of life imprisonment.
It was heinous because of the significant harm to others through delays in the case and Dawson's lack of remorse, Mr Everson said.
JC, who was also the family babysitter, was installed in the Bayview home as Dawson's partner days after he killed his wife.
He has consistently denied any involvement in his wife's disappearance, claiming she simply up and left her family home and children without a trace.
Justice Harrison had rejected this version of events as "ludicrous".
Two days after his guilty verdict, a lawyer for the ex-Newtown Jets rugby league player told the court his client had already received death threats while at Silverwater prison due to the high profile nature of the case.
The case shot into the public eye largely as a result of The Teacher's Pet podcast by The Australian's Hedley Thomas which garnered millions of views across the globe.
Dawson has already filed an appeal against his conviction.
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