A 25-year-old man raped a 42-year-old cleaner at knifepoint in a back alley in Serangoon Gardens after she thwarted his attempt to rob her, the High Court heard yesterday.

Singaporean Kelvin Singh pleaded guilty to a charge of rape and two charges of sexual assault by penetration for the offences that took place past midnight on Jan 13 last year. Four other charges, for attempted robbery, abduction, aggravated outrage of modesty and criminal intimidation, will be taken into consideration when he is sentenced at a later date.

He faces between eight and 20 years' jail and at least 12 strokes of the cane for each charge of rape and sexual assault.

The court heard that Singh, who had absconded from the Reformative Training Centre at the time, was cycling in Serangoon Gardens, looking for victims to rob when he spotted the woman.

The Chinese national, who cannot be named due to a court order, was walking home using her usual route after work. He followed her into a back alley off Worthing Road beside Kensington Park Condominium, got down from his bicycle and ran towards her, brandishing a foldable Swiss Army knife.

Suspecting that he was going to rob her, the woman threw her handbag containing about $800 over the fence into the compound of a house along the alley.

When Singh pointed his knife at her and demanded money, the terrified woman pointed at the house and told him "no money" in English.

Angered by the realisation that the woman had thrown her bag over the fence, Singh decided to have sex with her.

Holding the knife, he signalled for her to follow him to the end of the alley, where he forced her to perform oral sex on him and raped her after threatening her with the knife.

The woman did as she was told out of fear that he would kill her.

After the sexual assault, Singh used his right thumb to make a slitting gesture across his own throat, and warned her not to call the police, before cycling off.

The woman then phoned her boyfriend to tell him where she was. When the 38-year-old driver arrived, the woman told him about the foiled robbery but felt too embarrassed to mention the sexual assault.

The boyfriend called the police to report the attempted robbery.

Three days later, a member of the public alerted the police after spotting Singh cycling around the nearby Tavistock Avenue Park.

It is understood that police had asked residents to come forward if they had information regarding the incident.

When police officers arrived and identified themselves to Singh, he dropped his bicycle and fled on foot. He boarded a taxi in Ang Mo Kio Avenue 3 but was arrested after a brief chase.

A report by an Institute of Mental Health psychiatrist said Singh has prominent anti-social and narcissistic personality traits but did not suffer from any major mental illness. The report added that he did not appear to show genuine remorse for his actions and was at considerable risk of committing similar serious sexual or violent offences in future.

A psychiatric report on the victim five months after the rape stated that she felt down for about a week after the incident but hardly thinks about it any more.