A judge has described a BMX rider who sexually abused more than 20 young girls as a "monster of sexual depravity", whose crimes demonstrated the dangers of social media.
Fabian Meharry, 28, befriended 22 girls on social media websites before asking them to send him sexual photos of themselves.
He blackmailed the girls, aged between 11 to 17 years, into performing degrading and painful sexual acts on themselves online, secretly recording videos of them which he used to continue blackmailing them.
County Court Judge Liz Gaynor sentenced Meharry on Wednesday to 12 years' prison with a non-parole period of 10 years for more than 60 child sexual abuse crimes including producing child pornography, sexual penetration of a child under 16 and grooming children using a carriage service.
"Yours was prolonged, classically predatory, depraved, cruel and remorseless behaviour, which demonstrated with appalling clarity the dangers inherent in social media [that have required] the formulation of punitive legislation designed to protect, as far as it can, the young and vulnerable from persons such as yourself," Judge Gaynor said.
"It would not be unfair to classify you as a monster of depravity."
When his victims refused to perform sexual acts according to his instructions via webcam or Skype, he would threaten to publish the photos online or to send them directly to their families.
He also threatened to take his own life, filming himself holding a knife to his own throat.
Conversations where demands were made sometimes went from 30 minutes to three hours, and different victims were offended against for a day, weeks or months, with one abused for four years.
He also met some of his victims in person, when his crimes escalated into direct sexual abuse. One girl was blackmailed into performing acts of bestiality and incest.
Meharry - who is well-known in the Echuca BMX scene - told his victims about his internet business, which sold grinding wax for bikes and skateboards as a way to attract them to him, the court heard.
"It was as if you saw the internet as providing you with a vast array of vulnerable teenagers whom you could prey upon, exploit and terrorise, as the whim took you," Judge Gaynor said.
She said the sexual acts forced on the victims were often their first sexual experience.
They feared the world, had suffered difficulties in their families, felt guilty and blamed themselves.
Judge Gaynor said Meharry deliberately targeted young girls because they were able to be exploited to do what he wanted.
Older, more experienced women would be less likely to submit to his demands or believe his comments that he could not be caught and that they themselves had would be in trouble if they reported him to police.
His victims were from all over Australia. He knew how old most of them were. One was in court for the sentence and another appeared via video link.
The judge rejected Meharry's insistence he was now disgusted and shocked by his own crimes, saying he had had "ample opportunity" to stop before police ended his "nine-year reign of trauma".
He continued his crimes even after a police raid on his home in 2015, and another judge in 2008 warning him against sex with under-age girls, when he was sentenced for a sexual relationship with a younger child.
Judge Gaynor said his difficult family background and psychiatric reports did not explain his crimes.
She said he had "poor" prospects for rehabilitation.