He was 15 when he was coached to kill mastermind Anthony Ler's wife in 2001, and is now one of only two inmates serving time at the President's pleasure (TPP) after being convicted of a capital offence.
After being in jail for 16 years, he drew public notice again recently when he sought the President's clemency last November for his release. He was detained under a form of TPP, where anyone below 18 convicted of a capital charge, such as murder, kidnapping and drug trafficking, is spared the gallows because of his age and is jailed indefinitely.
His conduct and progress are reviewed periodically and the President can direct his release, based on a recommendation, if he is found suitable for release.
After the Criminal Procedure Code was amended in 2010, capital offenders under 18 are sentenced to life imprisonment instead of TPP, and have to serve a minimum period of 20 years before being reviewed for possible release.
Since 2012, three inmates detained earlier under TPP have been freed after being jailed for between 13 and 19 years. They were released before the 20-year mark because their offences were committed before the Court of Appeal's decision in the case of Abdul Nasir Amer Hamsah on Aug 20, 1997.
In this case, the Court of Appeal ruled that a term of "life imprisonment" meant imprisonment for the duration of the prisoner's natural life and not 20 years.
Before this decision, it was understood that life imprisonment sentences lasted for 20 years with remission, and a similar duration was used to review TPP detainees for release.
There is another form of TPP administered by the Singapore Prison Service that relates to people of any age acquitted of criminal offences because they were of unsound mind at the time of the offence.
Such people are reported to the Minister for Law, who may order that they undergo TPP detention.
There is no minimum period of detention, and their mental state is reviewed by psychiatrists every six months. If the review finds that they may be discharged without danger of injuring themselves or others, the minister may release them. During detention, they may be released into the custody of a friend or relative who gives security and promises to care for them properly and prevent them from injuring themselves or others.
A Prisons spokesman said those under this form of detention may be detained at the Institute of Mental Health or at prisons.
As of Dec 14, 2017, there were three offenders detained under this form of TPP. Two had committed murder and one had caused hurt with a dangerous weapon.
"(Ministry of Law) has conducted public consultation on proposed legislative amendments concerning the second form of detention, to introduce a maximum detention period and regular court review of the detention," said the spokesman.
In 2001, Z, as he was named in court papers, was just 15 when he knifed Ms Annie Leong. He killed her under the direction her estranged husband Ler, 34, who was convicted and executed in 2002.
He has been studying for a degree behind bars, and with testimonials backing his model behaviour in jail, is appealing to President Halimah Yacob to be considered for clemency and be set free.
His lawyer, Mr Peter Ong Lip Cheng, said yesterday: "My client is hopeful of his petition. He just marked his 32nd birthday in prison last week, as he has for the past 16 years. He has served all his formative years in jail and will live with this grave guilt all his life. He seeks the chance to return to the community and live with his parents."
Detained at the President’s pleasure
MUHAMMAD NASIR ABDUL AZIZ, 17
In 2008, Muhammad Nasir Abdul Aziz, who killed his lover's husband, was ordered by the High Court to be detained at the President's pleasure (TPP).
Nasir, 17, pleaded guilty to the murder but was not sentenced to death because of his age.
He was two months short of turning 17 when he stabbed disc jockey Manap Salip, 29, to death outside his 16th storey flat at Block 74, Whampoa Drive on July 1, 2007.
In 2001, a 15-year-old named Z in court papers knifed insurance agent Annie Leong, 30, as instructed by Anthony Ler, her estranged husband.
Investigations showed Z was manipulated and instigated by Ler to kill her so Ler could retain their Housing Board flat and custody of their daughter, who was then four years old.
Z attacked Ms Leong from behind at the fourth-floor lift landing of a block in Hougang on May 14, 2001.
She died later in hospital from multiple knife wounds to her neck and chest. He was convicted and sentenced to be detained at the President's pleasure given his age then, while Ler was convicted and sentenced to death. Ler was executed on Dec 13, 2002.
* Mohamed Redha Abdul Mutalib repeatedly stabbed his mother to death after hearing voices in his head which told him to do so in 2012. He had a history of substance abuse and was heavily intoxicated with pills, meant to treat a cough, when he attacked Madam Asnah Aziz in their Eunos home.
The 56-year-old housewife later died of multiple stab wounds. Two years later, Redha, then 32, was acquitted of murder in the High Court on grounds of temporary insanity.
Instead, he was held in custody at Changi Prison before being transferred to the Institute of Mental Health, where he was held at the President's pleasure.
* A then 16-year-old boy was detained at the President's pleasure for 20 years after he and Ramu Annadasvan, 26, assaulted a man with a gardening rake in 1981.
During the fight, Ramu instructed the boy to pour petrol on the victim. Ramu then set the man on fire. Ramu was hanged for the murder while the boy was detained at the President's pleasure.