In Christchurch's High Court today Cameron, 39, received a 19-year non-parole term as part of his life sentence for murder, and a 10-year preventive detention sentence for the sexual violation of Marie Davis.
Marie's mother Janet Davis read her victim impact statement to the court.
She told of a beautiful, intelligent and loving 15-year-old who was good at school and wanted to go to university.
The 12 days she was missing was a living nightmare, and her mother clung to the hope that her daughter had run away.
Her most important job was to be a good mother, and she had been cheated by Marie's slaying.
"I was so careful with my daughters, people said I was overprotective,
"He has destroyed my family for no good reason. I cannot understand why it had to happen."
Marie's sister Amy also read her victim impact statement recalling how she and Marie used to fight, laugh and cry together. "This was sudden, unjustified and cruel. She was stolen from us.
"Dean Cameron killed my little sister. I will never forgive him."
Crown prosecutor Kathy Bell said the rape and murder happened in Marie's own home where she should have been safe.
It was calculated and premeditated, and the health assessors' reports on Cameron had some difficulty in determining future risk in this case, she said.
Defence counsel Frank Hogan said Cameron wanted a finite sentence. He said this rape and murder had no chilling aspects, no suggestion of sadism, or long suffering.
This prompted a comment from the public gallery and Justice Lester Chisholm issued a warning that people would be removed from court if there were any more outbursts.
Mr Hogan said psychological and psychiatric reports showed no mental health issue with Cameron. He had normal intelligence and no personality disorder.
He said Cameron did not appear to lack insight, but had substance abuse and anger issues.
Justice Chisholm said he had sentenced Cameron to life imprisonment when the jury found him guilty of murder on June 11 this year.
He said Cameron overheard a conversation that Marie would likely be at home alone on April 6, 2008.
The jury accepted that he gained access to her house, raped her there and either murdered her or rendered her deeply unconscious.
He then took her to the Waimakariri River, weighed her down with rocks and put her naked body in the river.
She was not found until 12 days later.
Cameron's semen was found in her vagina and DNA evidence linked him to her home.
"You robbed her of her life, you robbed her of her future," Justice Chisholm said.
Cameron had a lengthy list of previous convictions including sexual violation and violence, and breaches of protection orders.
He had only been out of jail nine months when he committed this callous act, he said.
Justice Chisholm imposed a 19-year non-parole sentence for her murder, and considered preventive detention for the rape charge.
He said the community agonised over Marie's unexplained disappearance, and when she was discovered, had unbridled anger at her murder.
"It strikes at the very heart of communities, and is every parent's worst fear."
He said the reports he had read said Cameron was unwilling to discuss his offending, probably to preserve appeal rights.
The reports put him at a medium to high risk of recidivist sexual offending, and with a negative attitude to rehabilitation.
He said Cameron had no remorse or victim empathy, did not recognise his drug and alcohol problem, and had previously breached court sanctions.
He said that without insight Cameron would be an extremely high risk of reoffending, and that was a bleak outlook.
He imposed a preventive detention period of 10 years for rape.
After sentencing Janet Davis said she was pleased she had read her victim impact statement to the court as Cameron had to hear how he had affected the family.
She was surprised that he could look her in the eye while she did so, she said.
She was angry that he had shown no remorse, and felt it was not right that he could appeal the sentence.
