The question of whether a mildly intellectually disabled young offender who committed a serious offence should be sentenced to a long jail term with caning, or a stint of reformative training instead, has put a High Court judge in a quandary.

After weighing his "limited" options, Justice Woo Bih Li yesterday handed down a sentence of the latter for a teenager who committed rape when he was 14, even as he flagged the larger issues that went beyond the current case.

The prosecution had sought a jail term of between 15 and 18 years and caning of at least 15 strokes for the teenager, now 17.

While out on bail for other offences in 2014, he raped and sexually assaulted a 16-year-old girl, a stranger he followed to a lift lobby three doors away from her flat.

His assigned lawyers had argued for reformative training, a structured regime for offenders below the age of 21 that can last between 18 months and three years.

However, the prosecutors said reformative training should not be considered, pointing to the gravity of the offence and the egregious circumstances in which it had been carried out.

Justice Woo disagreed, and said reformative training was still an option as the rehabilitation of the accused remained a predominant consideration to be balanced against deterrence of crime and protection of the public. What troubled him was the accused's low IQ of 61.

"I would have had less hesitation in sending him to reformative training if he did not have any intellectual disability," said Justice Woo.

Prosecutors had argued that the accused was unlikely to benefit from reformative training as he lacked the requisite cognitive abilities to understand the programmes. However, Justice Woo said it was "oversimplistic" to say that reformative training should not be ordered just because the accused might not benefit.

The alternative was a long jail term and caning, the judge noted.

"Is that the answer? I do not think so," he said.

Justice Woo noted that the accused was himself a vulnerable person, in view of his young age and intellectual disability.

"It seems to this court that reformative training still offers the better prospect of rehabilitation when compared to imprisonment," said the judge, noting that there was a greater risk of the accused becoming a hardened criminal were he to be sent to prison.

Justice Woo said the case had exposed larger issues at stake, including the limited sentencing options available to a court faced with a young offender who has some intellectual disability. He said he would elaborate on these issues in a written judgment to be delivered at a later date.

The judge allowed an application by Deputy Public Prosecutor David Khoo for a stay of the sentence until the conclusion of any appeal.

The teen's lawyer, Ms Nadia Moynihan, had objected, saying he had spent the last three years in remand at the Singapore Boys' Home.