A mildly intellectually disabled teen was on home leave from the Singapore Boys' Home when he sexually assaulted a 10-year-old boy early last year, a court heard.

Woo Eng Loong was 17 when he performed oral sex and sexually abused the boy, who has a low IQ of 87, outside a shop in Maude Road at about 11.30am on Jan 30 last year.

Woo pleaded guilty in July.

Reformative training had not been recommended for the now 19-year-old, who was given seven years' jail yesterday. District Judge May Mesenas backdated his sentence to Feb 1 last year.

The court heard that Woo was loitering around his neighbourhood when he saw the victim and asked him if he wanted to "hang out". The victim told Woo to ask for his mother's permission.

When asked where he lived, the boy pointed towards a Housing Board block.

Woo then took the boy to the block, before leading the victim to a secluded area outside an empty shop.

There, Woo sternly told the victim to stand straight. Scared, the victim complied.

Woo suddenly pulled down the victim's pants and underwear to his ankles, and performed a sexual act on the terrified boy, who started crying. When the boy shouted for help, Woo covered his mouth as he struggled.

Woo turned the boy around to face the wall and committed another offence.

He then turned the victim around again and took off his own pants, before asking the boy to do the same. But the boy pulled up his pants and underwear, grabbed his bag and ran home. The boy's father later made a police report.

Pressing for at least seven years' imprisonment, Deputy Public Prosecutor Chee Ee Ling said that the protection of the public is of paramount importance.

She referred to Woo's serious offences and his inability to be rehabilitated due to his low IQ, lack of familial support and his propensity to target vulnerable young males.

She said the victim was young and especially vulnerable, with a low IQ. She also said that the offences committed by Woo were premeditated.

Woo, who has previously been convicted for theft, mischief, theft in dwelling, fraudulent possession and a rash act, has also been assessed to have a moderate to high risk of reoffending, she added.

Woo's pro bono lawyer Christopher Sim said in mitigation that his client has shown remorse and comes from a poverty-stricken family. His mother and sister also have low IQ, Mr Sim told the court.

The maximum penalty for sexual assault by penetration is 20 years' jail and the offender may also be fined or caned.

Elena Chong