Robert John Faragher, then 28, was going through a "turbulent time" when he contacted the 13-year-old, a Brisbane court has been told.
He was on parole, using cannabis heavily and feeling alone after a toxic relationship ended with his partner leaving.
Faragher portrayed himself as a 16-year-old in a dating profile, while the girl admitted her age when he collected her from home before taking her to a deserted location.
He offered her cannabis which he also smoked before touching and sucking her breasts, licking her vagina and twice attempting to penetrate her, the Brisbane Supreme Court was told on Thursday.
After the girl went to police, detectives searched Faragher's house, finding evidence of an unsophisticated cannabis business that involved 38 supplies to about 10 customers over about three months.
He advertised different cannabis strains to his customers and that he had the drug available at a good price.
Police also seized cannabis plants from the backyard and drug paraphernalia.
The full extent of the trafficking was not known as encrypted applications were used, Justice Rebecca Treston said in sentencing Faragher.
She took into account the girl was 15 years younger than Faragher when he committed persistent and protracted offences.
"Your actions in using an online profile misrepresenting your age when the girl in question was 13 … is terribly concerning," Justice Treston said.
The unprotected sexual acts Faragher instigated put the child at risk of disease, while sharing cannabis to encourage her compliance had a predatory element, she added.
It was also of serious concern that Faragher told police he found a 16-year-old more attractive than older women.
Justice Treston accepted Faragher, who began taking drugs after becoming involved with a bad crowd, recognised he had made bad choices.
She handed down a head sentence of three years and three months behind bars, ordering Faragher, now aged 29, be immediately eligible to apply for parole.
Faragher pleaded guilty to charges including four counts of indecent treatment of a child under 16, two counts of attempted penile intercourse with a child under 16 and one count each of trafficking and supplying a dangerous drug to a minor.
He has been in custody since his arrest while on parole in November 2022, initially serving a suspended sentence for the previous trafficking conviction.
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