An Australian teacher who killed his wife so he could start a new life with a teenage student has been sentenced to an extra year in prison for a crime committed when the girl was 16 years old.

Chris Dawson, 75, sat with his head in his hands as he awaited the sentence on Friday from a room inside Long Bay Correctional Complex, south of Sydney, where he is already serving a 24-year sentence for killing his wife, Lynnette.

Lynette’s disappearance in the early 1980s became one of Australia’s most intriguing mysteries, confounding police for decades and inspiring a podcast that delved into the whereabouts of the mother, whose body has never been found.

On Friday, Judge Sarah Huggett sentenced Dawson to three years in prison on one charge of “carnal knowledge upon a girl above the age of 10 and under the age of 17” for a sex act committed in 1980.

The sentence comes with a non-parole period of two years, so the net effect will an extra year in prison for Dawson before he’ll eligible for parole in August 2041, Huggett said.

At the time of the offense, Dawson was a teacher around 32 years old, who took active steps to become the girl’s teacher by singling her out and telling her she was beautiful, the court heard.

Huggett said Dawson did not use threatening words or conduct “to secure the victim’s consent and silence” but there was a “degree of manipulation and exploitation.”

Dawson knew the girl was having trouble at home and told the victim “what he was doing was effectively something the victim needed and/or that it would be helpful,” she said.

“The offense was committed on a Friday or Saturday night when the offender took the victim to his parents’ home … He told her his parents were away at their holiday home, it was nighttime and no one was home,” Huggett said.

The court heard that Dawson and the girl engaged in a lawful sexual relationship for many years after she turned 17 and later married and had a child.

Their relationship continued despite intense speculation about the whereabouts of Dawson’s wife Lynette, who Dawson had claimed walked out on their family when their children were just two and four years old.

No trace of Lynette Dawson has ever been found despite multiple police investigations and searches, which included digging up the backyard of the couple’s former home on Sydney’s northern beaches in 2018.

Dawson has continued to maintain his innocence, even after being found guilty in 2022 of murdering Lynette sometime around 1982.

During the judge-only trial, multiple witnesses claimed to have seen Lynette Dawson in the years after, but Judge Ian Harrison dismissed those as false or mistaken.

Harrison said that while the verdict was unsupported by direct evidence, he was satisfied by the Crown’s submission that Dawson had become infatuated with his student, to the extent that he saw no other way to be with her than to kill his wife. (CNN)

•PHOTO: Chris Dawson and team arrive at NSW Supreme Court on August 30, 2022 in Sydney, Australia. Lisa Maree Williams/Getty Images/FILE

Update news