Almost 40 years after killing his wife Lynette and disposing of her body, former Sydney schoolteacher Chris Dawson will spend at least 18 years in jail.

On Friday, Justice Ian Harrison delivered a maximum sentence of 24 years in the NSW Supreme Court after finding the 74-year-old guilty of murder in August.

“In my opinion the murder of Lynette Dawson is an objectively serious crime,” Justice Harrison said while sentencing Dawson.

“Lynette Dawson was faultless and undeserving of her fate.”

The decision concludes a four-decade long wait for justice for Mrs Dawson’s family, who are still pleading with the convicted wife-killer to reveal the location of her body.

Dawson was given a non-parole period of 18 years, meaning he will be aged in his 90s before he can apply for release from jail.

The court heard that Dawson’s health was deteriorating, and he shows signs of chronic traumatic encephalopathy, a brain condition often experienced by those who play contact sports.

Justice Harrison acknowledged Dawson’s health issues.

“Mr Dawson is not old by contemporary standards, but the reality is he will not live to reach the end of his non-parole period, or will alternatively, by reason of his deteriorating cognitive condition and physical capacity, become seriously disabled before then even if he does,” he said.

“I recognise that the unavoidable prospect is that Mr Dawson will probably die in jail.”

Mr Dawson has never revealed the location of his former wife’s body.

Dawson murdered his wife in January 1982 to have an unfettered relationship with a high school student who was also his babysitter, known as JC.

During the sentence hearing in November, 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.

Dawson’s lawyer Greg Walsh disputed claims the crime was at the high end in terms of objective seriousness.

Mr Walsh said the former Newtown Jets rugby league player had already suffered under the “most constant and egregious publicity” for four decades.

Outside court, Mr Walsh said his client still maintained his innocence despite the guilty verdict and his daughter’s plea to reveal where her mother’s body was.

“I’m innocent. I don’t know where she is because I didn’t murder her,” Dawson allegedly told Mr Walsh.

Mr Walsh said there were no winners in such a case, with Mrs Dawson’s family and the community suffering and Dawson himself likely to spend the rest of his days in jail unless he is successful in appealing the conviction.

“It’s a very, very sad case indeed. You see the family there and they’re suffering. They’re feeling it and they’ve felt it for a number of years,” he said.

Mr Walsh, who has represented Dawson for four-and-a-half years, said he would step down from the role. Public defender Belinda Rigg SC will take his place.

Dawson has filed an appeal against his conviction.

Ms Dawson’s brother Greg Sims also spoke outside court.

“Today marks the end of a very long, painful and challenging journey. At last we have justice for Lyn and that was our main aim,” he said.

“Chris Dawson discarded her, the Dawsons disregarded her. From today on we would like her to be known and remembered as Lynette Joy Simms.”

He said he hoped Dawson would live a long life so that he could serve the sentence imposed on him.

“We really didn’t believe this day would ever come. What we need now is to find Lyn and put her to rest. It’s our time to begin living our lives without having this hanging over our heads. Chris Dawson has had 40 years of freedom. Now it’s our turn.”

1800 RESPECT 1800 737 732

Lifeline 131 114

– with AAP