A sexual attack on a teenage girl in a Christchurch park has drawn a jail term for an intellectually disabled man.Judge David Saunders today sentenced Tailiauli Aso, 31, to a three-year, two-month prison term for his assault on the girl in April, 2010.Aso had a Samoan-language interpreter in court, and a psychological report assessed him as having a low level of intellectual functioning - said at an earlier court session to be about that of a 10-year-old.The incident occurred in a Hornby street when Aso encountered a girl walking home.He yelled that he wanted to see her, but she ran away and went into Denton Park, where he grabbed her by her clothing and pushed her to the ground and held her there for a short time.Aso then sexually assaulted her, but she was able to push him off and escape.He pleaded guilty to the charge of assault with intent to commit sexual violation. His criminal record shows convictions for indecent assault in 2003 and 2005.