Over the past 30 years, Quek Yah Chiang has repeatedly molested children and young people.
Two years ago, a 13-year-old girl suffering from moderate mental retardation became his fourth victim.
The 66-year-old was sentenced to 21 months jail yesterday.
Quek, then manager of a maid agency, has a history of sexual offences against youngsters, dating back to 1985. His youngest victim was an 11-year-old boy.
In his latest case, Quek had spotted the girl in her school uniform, sitting on a stone bench in an MRT station on May 2, 2012.
He approached the girl, held her left hand and chatted with her. She cannot be named as she is a minor.
Posing as a teacher, he boarded the train with her. They alighted at Paya Lebar and she followed him to the Singapore Post Centre, near the MRT station.
Quek led her to a secluded staircase where he hugged and kissed her.
He also undressed her and performed indecent acts on her.
Throughout the ordeal, the girl did not dare to move as she was afraid he would hit her, court papers said.
When he had completed the lewd acts, he kissed her on the lips and made her promise not to tell anyone what had happened. He also gave her $4 in lunch money.
When she arrived home, she told her family what had happened and they lodged a police report that night.
She also visited a clinical psychologist. She mentioned she was frightened of Quek after the incident and required her family to ensure her safety, court papers said.
Quek was arrested and pleaded guilty in August this year.
His lawyer, Mr Peter Fernando, said his client was suffering from depression at the time.
In sentencing, District Judge Christopher Goh said he had committed a serious offence and that Quek had taken advantage of a vulnerable, young victim.
He also took note of Quek's past offences.
Quek, who was dressed in a blue shirt and black pants, was accompanied by four family members yesterday. They appeared calm throughout the hearing.
Later, a woman in her 60s believed to be Quek's sister told TNP outside the courtroom that she was not happy with the sentence, as it was too harsh. "Of course I am not satisfied," she said, raising her voice as she spoke.
"It's not as if he killed someone," she added, before another family member ushered her away from this reporter.
She then broke down and sobbed uncontrollably as the other family members consoled her.
Dr Ken Ung, a consultant psychiatrist at Adam Road Medical Centre, said offenders like Quek return to their old ways for the thrill and sexual gratification.
"It's a sexual deviation where they feel like they have total power and control (when molesting someone).
"But it's a myth that all such offenders re-offend. Quite a lot of them do not."
This article was first published on October 25, 2014.
Get The New Paper for more stories.