SINGAPORE - He was dubbed the Clementi monster, a young man with a penchant for sexual violence.
Groping his victims was not enough of a thrill. He needed to entrap, humiliate and hurt them as well. In 1998, then 16 years old, he was convicted of four counts of aggravated outrage of modesty after he stripped and molested female classmates.
He was sent to the Singapore Boys' Home, but after he breached home discipline, was transferred to a Reformative Training Centre (RTC).
Time in an RTC did not cure him.
Weeks after his release in 2004, he went on the prowl again, just minutes from where he lived. Between 2004 and 2005, Sashi Kumar Pubalasingam savagely attacked three women, including one who was then 67.
In 2006, he was jailed for 20 years and ordered to receive 24 strokes of the cane.
Psychiatrist Adrian Wang said that such perpetrators usually have anti-social or sociopathic traits. They are unable to feel remorse and empathy for their actions.
He added: "Combined with poor impulse control and aggressive tendencies, these people could invoke violence on others - both physically and sexually. Some do so out of sheer self-gratification or the mere thrill of seeing another person suffer."
Over the years, a number of sexually violent criminals have been locked up, only for some of them to re-offend after their release.