"He approached her and told her that he had been watching her," Judge Bell said. "The offender indicated to the victim that he could help her if she would help him, and indicated his groin."

Aiken then led the woman to some public toilets, where she performed sexual acts on him. Afterwards, in what Judge Bell described as a "cold-blooded act of theft", Aiken rifled through the woman's purse and stole $200, which he spent at Burwood RSL. The woman alerted Westfield security and Aiken was soon arrested.

Today the 31-year-old was jailed for up to four years after pleading guilty to sexual intercourse without consent, indecent assault and theft over the incident on June 9 last year. "He's taken advantage of a woman in a very vulnerable situation," Judge Bell said.

"She thought that he was a security officer ... but he didn't do anything to dissuade her from thinking he was. "She was vulnerable because she had been caught herself engaging in acts of illegality." Aiken's wife wept in the public gallery as the judge noted the devastating impact of the offender's behaviour on his family and the "domino effect of what was an act of lust".

With her husband in jail and shamed by what had happened, Aiken's wife had sent their two young children to stay with her parents in Vietnam. In line with Vietnamese custom, she had tried to offer reparation to the victim, an acquaintance, only to find herself charged with approaching a prosecution witness.

"Her distress, I'm sure, is as much as that of the victim, if not more," Judge Bell said. He praised her for standing by her errant husband, saying "some women might feel that this was sufficient justification for turning their back on the man". Judge Bell said Aiken was on a bond for assault at the time of the offences and his lengthy criminal history included a conviction for indecently assaulting a child under the age of 10.

"He obviously needs some assistance in learning to control his sexual drive," he said. Judge Bell jailed Aiken for a maximum of four years for the sexual assault, 16 months for the indecent assault and 12 months for the theft, ordering him to serve at least 12 months for each offence.

With time already spent in custody, Aiken will be eligible for parole in June.

AAP