On 25 October 1997, near Dhoby Ghaut MRT station, 18-year-old Png Hock Seng (; also spelt Phng Hock Seng), a full-time National Serviceman and member of the Sio Gi Ho gang, was attacked by seven members of the Sio Koon Tong gang, which operated at Orchard Road. Png died from a stab wound inflicted on his back. The seven offenders, all youths between 16 and 19, were charged with murdering Png, whom they erroneously believed to be a member of a rival gang.
The charges of murder against all seven accused were eventually reduced and the youths were thus convicted of lesser charges; out of all the seven, the main offender Allan Tan Kei Loon () was found guilty of the most serious charge of manslaughter, and sentenced to seven years' jail and nine strokes of the cane, despite the prosecution's request for the maximum sentence of life imprisonment and 24 strokes of the cane. Although the prosecution's appeal to raise Tan's sentence from seven years to life had failed, Tan's sentence was nonetheless increased to ten years' jail and 15 strokes of the cane. The remaining six offenders were convicted of rioting and jailed between 18 and 30 months with caning.
Death at Dhoby Ghaut MRT station On the night of 25 October 1997, an 18-year-old full-time National Service man was stabbed to death by a group of youths outside Dhoby Ghaut MRT station.
The victim was identified as 18-year-old Png Hock Seng, a Singaporean citizen who resided in Yishun with his parents and elder sister, and he only enlisted for two months at the time of his death. The police responded to a report about an alleged fight taking place at the nearby area, and they arrived to find Png, who was stabbed once on the back and also suffered multiple bruises and injuries on his body. Png was later pronounced dead on the way to Singapore General Hospital and his family never got there on time to see him one last time. An autopsy report by Dr Gilbert Lau revealed that single stab wound on Png's back measured about 20 to 22 cm deep and it penetrated the liver and kidney and the left chest, and it also severed the blood vessels, and the injury was sufficient in the ordinary course of nature to cause death.
According to his sister and parents, Png was a filial and obedient son and brother who had a close relationship with his family. Png's sister said that due to the family's poor financial situation, her brother wanted to sign on as an army regular in the Singapore Armed Forces (SAF) and earn money to allow his 20-year-old sister, a polytechnic student, to further her studies overseas, and the last time she saw her brother was at around 6.30pm before he went out. Png's father said that while his son had a short temper, he loved singing, liked making friends and often hang out with them at karaoke lounges, and he would never argue with anyone else. In fact, Png was supposed to go out with his friends for a karaoke session that night before he was murdered. Witnesses testified that they saw an injured Png running for a distance before he collapsed and became motionless, and several drivers stopped their cars and alighted to tend to Png. Png's two friends, who were together with him at the time the attack happened, assisted the police in their investigations into Png's killing.
Arrest and charges The police classified the death of Png Hock Seng as murder, and the Special Investigation Section of the Criminal Investigation Department (CID) was put in charge of the investigations.
On 31 October 1997, a 16-year-old youth named Benedict Kho Lian Teck (), allegedly a member of a gang, was reportedly arrested and charged with murder for allegedly causing the death of Png Hock Seng. Kho was the first suspect to be charged in this case. District Judge See Kee Oon ordered Kho to be remanded in police custody to assist in police investigations.
On 1 November 1997, 18-year-old Ong Kian Heng () became the second person to be charged with murder. Three days later, on 4 November 1997, 18-year-old Koh Boon Wee (; alias Martin Koh) was charged with Png's murder. Although this went unreported, the police managed to arrest four more suspects, and altogether, seven teenagers, who all belonged to the same gang an aged between 16 and 18, were apprehended and found to be responsible for the murder of Png Hock Seng.
Although all the seven youths were together charged with murdering Png Hock Seng, it eventually became known by June 1998 that only one of them, 18-year-old Allan Tan Kei Loon (born 13 October 1979), who surrendered himself on 4 February 1998, was left facing a murder charge while the other six teenagers had their charges reduced. Offenders aged 18 and above could be sentenced to death under the law if found guilty of murder.
Motive and attack The following was the official version of the murder of Png Hock Seng, based on the court documents, statement of facts provided by the seven accused and evidence collected by the police.
It was recounted that prior to the murder, Benedict Kho Lian Teck, one of the youths involved in the murder, and his friends were attacked by several members of the Sio Gi Ho gang at Bugis Junction shopping mall. Kho, who belonged to the Sio Koon Tong gang, sought the help of his own gang to seek revenge, and six members of the gang, together with Kho, were dispatched to look for the Sio Gi Ho gang and retaliate. The seven members gathered at Dhoby Ghaut MRT station, where they encountered Png and his two friends coming out of a taxi. The group approached Png, and asked him which gang did he belong to. Png, who happened to be part of Sio Gi Ho but was not involved in the earlier gang clash, replied that he was a member of Sio Gi Ho, and upon receiving the answer, the group started to attack Png without further verifying any of his involvement in the incident.
One of the youths, identified as Yeo Hsi Tsung (), allegedly stood guard over Png's two friends on the side and stopped them from intervening, while the rest sprang upon Png, who was kicked and punched multiple times. At one point, while Png was keeling down and warding the blows by covering his head, one of the attackers, Allan Tan Kei Loon, charged at him and plunged the knife into Png's back only once. Tan had earlier bought two knives and provided one for one of his fellow gang members while arming himself with the other. This single stab wound inflicted by Tan mortally wounded Png and he died soon after the group ended their attack upon seeing that he was down.
Trial proceedings Trial of the first four accused On 17 June 1998, four of the seven offenders became the first to stand trial for their roles in the murder of Png Hock Seng. The four youths - 17-year-old salesman Benedict Kho Lian Teck, 18-year-old Ong Kian Heng, 18-year-old sales promoter Koh Boon Wei and 18-year-old food stall assistant Yeo Hsi Tsung - pleaded guilty to lesser charges of rioting before District Judge Daniel Koh, who reportedly quoted that it was disconcerting to see the rise in rioting offences being committed in public. Official statistics showed that there were a total of 478 rioting offences committed in 1997, 518 in 1996 and 361 in 1995.
Out of the four, Kho was sentenced to 18 months' jail and five strokes of the cane, while both Koh and Ong were each given five strokes of the cane and 24 months' jail, and Yeo received the most severe sentence of 30 months' jail and five strokes of the cane. Aside from this, Yeo, who was previously convicted of becoming part of an unlawful assembly, faced an unrelated charge of rioting in March 1996 and received a concurrent 12-month sentence, and both Ong and Koh were each given a concurrent sentence of six months' jail for association with an unlawful assembly in September 1996, and a third charge of theft against Ong was taken into consideration during sentencing.
Trial of Allan Tan Kei Loon On 8 August 1998, 18-year-old Allan Tan Kei Loon, who formerly worked as a part-time waiter, stood trial for the killing of Png Hock Seng. By then, Tan's original murder charge was reduced to culpable homicide not amounting to murder, also known as manslaughter in Singapore's legal terms. The reduction of the charge allowed Tan to escape the death penalty for murdering Png, but he faced a possible sentence of up to ten years' jail or life imprisonment with a possible fine or caning. Tan pleaded guilty before Judicial Commissioner Tay Yong Kwang at a hearing convened at the High Court.
The prosecution sought the maximum sentence of life imprisonment and 24 strokes of the cane for Tan, and Deputy Public Prosecutor (DPP) Foo Cheong Ming highlighted that the violence exhibited was "wanton and senseless" by nature, and the fatal attack on Png was "brutal, savage and unjustified". He stated that Png had in no way caused any provocation despite being the rival gang member and the killing of Png took place on a Saturday and in the public, and the prosecution stated that Tan should be severely punished with the highest penalty possible to uphold the need to safeguard public safety and order.
On the other hand, the defence lawyer Fong Weng Khai submitted in mitigation that Tan's father, with whom Tan was close to, died of throat cancer three years ago in July 1995 and it was an emotional blow to Tan, who could not concentrate on his studies and gave up retaking his N-levels, and compounded by his mother's loss of her job as a hawker and his younger brother bring transferred to his relatives' care due to financial difficulties, Tan had to work in various jobs and subsequently joined the gang for protection while he worked as a waiter in a Boat Quay restaurant. he asked for leniency for Tan.
By the order of Abdul Nasir Amer Hamsah's landmark appeal on 20 August 1997, life imprisonment is to be defined as a term of incarceration lasting the remainder of a convict's natural life, instead of the old definition of life imprisonment as 20 years in prison. The changes to the law was to be applied to future cases that took place after 20 August 1997. Since Tan committed the crime of manslaughter on 25 October 1997, two months after the landmark ruling, and if he were to be sentenced to life in prison, Tan would be imprisoned for the rest of his natural life.
On that same day, Judicial Commissioner Tay Yong Kwang delivered his decision on sentence. He rejected the prosecution's arguments for life imprisonment in Tan's case, stating that he took into consideration both Tan's lack of criminal records and his young age of 17 or 18 at the time of the killing, and he also pointed out that with life imprisonment being presently construed as a natural life jail term rather than 20 years, he decided that it would be manifestly excessive to allow Tan be jailed for the remainder of his whole life after balancing out the aggravating and mitigating factors of his case. As such, Judicial Commissioner Tay sentenced 18-year-old Allan Tan to seven years in jail and nine strokes of the cane.
Trial of the last two youths It was confirmed through the Chinese newspaper Lianhe Wanbao coverage of Tan's sentencing that the remaining two offenders, identified by Chinese newspapers as Andy Ng Guohao () and Stanley Chin Jiachun (), would stand trial the following week after Tan's trial, but the duo's sentences or convictions were not made known to the public.
Prosecution's appeal of Allan Tan's sentence