Tomo told police at the time that he had been in a consensual sexual relationship with the woman since he was 10 or 11. He also said he had consensual sex with her two nights prior to the reported incident.
In court today, Crown prosecutor Ngaroma Tahana said there was never a consensual relationship between the pair.
"There is a number of aggravating factors, the vulnerability of the victim, it was well established her intellectual disability, the harm that she suffered . . . and premeditation, there was an element of forward planning given [Tomo] knew of her home and where she lived at the property - there was an element of home invasion as she was entitled to feel safe," Ms Tahana said.
"Mr Tomo has little insight into the offending and continues to maintain he's innocent."
Defence lawyer Harry Edward said there was familiar contact between Tomo and the victim.
"[Tomo] has a certain naivety and lack of sophistication, he doesn't have the ability to cast his mind to her shortcomings," Mr Edward said.
A pre-sentence report stated Tomo was in a relationship with the victim and did not have the means to assess her disability. Judge Weir rejected this, saying it took Tomo's claims only and did not interview the victim.
He described claims there was an ongoing sexual relationship between the pair as "fanciful" and that there was consensual sex two days prior as "unbelievable".
"What is also unbelievable is your assertion as far as you were concerned that she was completely normal. Her disability was clearly pointed out by the psychologist. I observed myself the complainant in the witness stand clearly suffers from significant cognitive and intellectual disabilities," Judge Weir said.
"Giving evidence was quite painful for her and being cross-examined she was saying 'I want my mum'. You knew what the position was with her."
In a victim impact statement the victim's mother said her daughter was still extremely traumatised by what happened to her. She has had to go to the doctor a considerable amount of times, who was considering prescribing anti-depressants.
There was also a deterioration in her self-confidence and the victim was undergoing counselling, Judge Weir said.
"So far as mitigating factors - there are no mitigating factors. You lack insight and there is no remorse. There is nothing to assist me and provide any reduction to you on these charges," Judge Weir told Tomo.