An Australian physical education teacher who murdered his wife so he could start a new life with a teenage student has been found guilty of sexual abuse.

Judge Sarah Huggett of the Sydney Downing Centre District Court on Wednesday convicted Chris Dawson on a charge of “carnal knowledge upon a girl above the age of 10 and under the age of 17.”

The charge relates to the same student Dawson began a new life with after murdering his wife Lynette in 1982. He later married the student and had a child with her, but the pair later divorced.

Dawson was found guilty last year of murdering his first wife Lynette in a conviction that ended one of Australia’s longest-running cold cases.

He had long denied the murder, claiming Lynette had left him and their two young children before disappearing.

The student, who can be identified only as AB, alleged Dawson had sexually abused her in 1980, when she was a 16-year-old pupil in one of his classes at Cromer High School in Sydney.

Dawson, who appeared in court via video link from Sydney’s Long Bay jail, had denied that, claiming he began the relationship with AB when she was 17 and no longer his student.

Judge Huggett sided with AB, finding that Dawson had groomed the teenager while she was still his pupil.

AB said she began babysitting for Dawson when she was 16, often staying the night at Dawson’s house.

“He asked me to marry him when I was 16, many, many times, I always felt obligated,” AB had alleged.

Judge Huggett said she accepted the evidence that Dawson had proposed to AB at least once in 1980, when AB was 16.

The judge established there was “powerful evidence” within a 17th birthday card sent by Dawson to AB in early 1981, in which “the accused, a mature man, as opposed to an immature teenager, was confident in the existence of a reciprocal and permanent relationship. And that was because a sexual relationship had commenced” in 1980.

Dawson dedicated the card to “the most beautiful girl in the world” and wrote “knowing we will share all the birthdays to follow.”

The body of Dawson’s wife has never been found. He is not eligible for parole as long as the body remains missing.

AB had testified against Dawson in the murder trial, which saw Dawson jailed for 24 years. The judge in that case found allegations that Dawson had sexually abused his 16-year-old student in 1980 were “truthful and reliable” and that Dawson’s obsession with the teenager was enough to motivate him to kill Lynette.

Dawson responded to Wednesday’s verdict by swearing repeatedly.

He will be sentenced on the “carnal knowledge” charge on September 15. (CNN)

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