Former teacher and convicted wife-killer Christopher Dawson will have to wait one year more to be eligible for parole over a sexual relationship with one of his students four decades ago.
The 75-year-old groomed his victim, leading her into sexual activity at his parents' home and taking advantage of her vulnerability due to troubles in her home life, Judge Sarah Huggett found on Friday.
The judge sentenced Dawson for three years commencing August 30, 2039 with a non-parole period of two years.
This total sentence will be entirely subsumed by the 24-year jail period imposed for the murder of his wife Lynette Joy Dawson with the only practical effect being that he will now be eligible for parole one year later on August 29, 2041.
Dawson was sentenced at Sydney's Downing Centre District Court after being found guilty of carnal knowledge as a teacher of a girl over 10 and under 17.
He plans to appeal the June verdict.
Ahead of the sentencing, crown prosecutor Emma Blizard said the teacher's offending was not a one-off but rather a course of conduct that led to his student being groomed over an extended period.
She told Judge Sarah Huggett that Dawson had exploited the victim's vulnerability as part of his crime.
Dawson appeared by video-link from Long Bay prison wearing prison greens and waved to his lawyer as he appeared.
Ms Blizard said the offence was in the middle range of objective seriousness, pointing to the age difference between the teacher and his victim as well as his breach of the trust she would have had in him.
Dawson's lawyer Claire Wasley argued that the objective seriousness was lower because the victim was 16 years old and towards the maximum age of 17 set down by law for the offence.
The crime is the 75-year-old's second conviction after he was last year found guilty of murdering his wife Lynette and disposing of her body in January 1982.
Dawson planned the murder to pursue an "unfettered relationship" with the teenage student, who cannot be legally named.
While he was still married and living with Lynette, he groomed the girl and ultimately engaged in sexual activity with her before the end of the school year in December 1980.
He pleaded not guilty at his trial, although he did not dispute the pair had a sexual relationship.
Dawson's public-defence lawyer instead argued the sexual activity began when the student was no longer in the teacher's class.
The student said they first engaged in sexual activity at the Maroubra home of Dawson's parents, who were out of town.
Former students at the same Sydney northern beaches school described seeing her sitting in Dawson's lap and him standing between her legs on school grounds and in his office.
However, Friday's sentence is unlikely to affect how long the 75-year-old spends in jail.
He received a 24-year sentence for murdering Lynette Dawson, whose body has not been found after her disappearance in 1982.
Laws preventing his parole before he discloses the location of her body mean he is expected to never be released.
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National Sexual Abuse and Redress Support Service 1800 211 028
© AAP 2023