On a Sunday he was allowed to go home fom the Singapore Boys' Home last September, a teenager raped his older sister when he got back.

The 16-year-old pleaded guilty in the High Court today but the case was adjourned for an independent psychiatric assessment.

His lawyers felt that he could be emotionally scarred as he had been sodomised by an elder brother, who also raped the same sister in 2002.

His brother, now 20, is serving sentence.

The court earlier heard that a psychiatrist at the Institute of Mental Health (IMH) had found the sister, who is two years older, to be mildly retarded with an IQ of 64, lower than the normal 90 -100.

She was raped in her bedroom of their four-room HDB flat at 4.20pm while the mother was sleeping in the master bedroom and an 11-year-old brother, who is also mentally retarded, was in the living room.

The offender then returned to the Boys' Home with his mother. The raped sister decided to tell an uncle living nearby.

The uncle called the mother and told her but her son bolted as they were approaching the uncle's flat.

He was arrested five days later.

He had been placed in the Boys' Home for two years for committing robbery with some friends in April 2005, while on probation for burglary, receiving stolen property and inhalant abuse.

An IMH psychiatrist found him to be beyond parental control and without the capacity and motivation to change for the better.

None of them can be named to protect the identity of the victim.