A martial arts teacher who sexually offended against a teenager has been jailed for at least 18 months.
Aaron Smalley, now 29, met the girl when she was in primary school and got to know her more as she took martial arts lessons from the age of 10.
He began to sexually assault her when she was 15 and he was then 26.
The offending began in the back of his car after a fitness exhibition.
He began to have sex with her after she turned 16 and on Tuesday was convicted of 13 charges including sexual assault of a child aged under 16, and sexual penetration of a child aged 16 or 17 under his care, supervision or authority.
The offending took place in secret locations, including at a martial arts venue and his mother's home.
County Court Judge Michael O'Connell jailed him on Tuesday for three years and seven months, ordering him to serve at least 18 months before he's eligible for parole.
The young woman said she felt as if the most crucial years of her teenage life had been taken from her by her involvement with Smalley.
She felt hurt, betrayed and anxious. She had once loved martial arts but had to stop attending classes because of Smalley's offending.
After reporting it to police she secretly recorded Smalley in a conversation, prompting his arrest. He confessed when interviewed by officers.
But he was supported during his sentencing by a former Victoria Police officer who had investigated sexual crimes.
Bronwyn Cook described him in a reference as loving, caring and at times naive.
She watched the sentencing on Tuesday and said she had spoken with Smalley at great length about the inappropriateness of his relationship with the young woman and while he hadn't comprehended the imbalance of power at the time, he does now.
Judge O'Connell said Smalley's offending breached the trust placed in him by the young woman and her parents.
"She clearly looked up to you as her coach," he said, noting when asked to write an assignment for school on a significant adult of of influence in her life, she had chosen him.
He said the offending was not spontaneous, but was considered, frequent and sustained over six months between October 2018 and mid-2019.
While an expert assessed him as a moderate risk of re-offending, Judge O'Connell found he had excellent prospects for rehabilitation.
