In a third case, Teo failed to report to the police while under supervision, and hence he spent one year in prison after his conviction for the offence on 23 April 1963.

Teo was convicted a fourth time on 2 December 1965, when he committed armed robbery with several other people, and hence he was sentenced to three years' imprisonment.

In his fifth case, Teo was found guilty of criminal breach of trust and on 3 September 1966, he was given a jail term of ten months.

[1] On 26 March 1969, Teo Cheng Leong, then 36 years old, teamed up with three men to commit armed robbery at Sims Avenue, Geylang.

On the afternoon of that day itself, Teo and his three accomplices – Ng Chwee Bock (黄水木 Huáng Shuǐmù), Khoo Meng Hwa (邱明华 Qiū Mínghuá) and a third person whose identity remains unknown – barged into the shophouse of 39-year-old cobbler Chew Sin Kok (赵善国 Zhào Shànguó), and out of the four, Teo and one of his accomplices each wielded a gun while the remaining two were armed with knives.

While Chew was outside the shop and having lunch, the robbers held the other occupants of the shophouse hostage, and they robbed Chow Sow Lin (周秀莲 Zhōu Xiùlián), a housewife and mother of four (two sons and two daughters), of her valuables (worth about S$1,000) and S$1,000 in cash, as well as two wrist watches, a camera and radio.

Feeling peculiar, Chew went to the back of the shop and he noticed his 30-year-old colleague Cheok Yan Soo (石贤斯 Shí Xiánsī), who was one of the hostages of the holdup, looking down at him from the two-storey window and beckoning him to call the police to catch the robbers.

Inspector D'Oliveiro, who allowed several men to enter his car, chased after Teo, who eventually reached an empty hut in the forest, which belonged to a furniture maker.

[6][7] Another of Teo's accomplices, 33-year-old Ng Chwee Bock, surrendered himself to the police two days after Khoo was captured, making him the third person to be apprehended for the robbery.

The two men pleaded guilty to armed robbery charges in February 1970,[9] and during the same month, both Ng and Khoo were each sentenced to ten years in prison.

[10] As for Teo, he was charged with both armed robbery and illegal discharge of firearms, the latter offence which attracted the death penalty under Singaporean law.

15 years later in 1984, PC Quek, who by then was promoted to Corporal, would engage in a gunfight with infamous gunman Khor Kok Soon, whom they caught trying to commit firearm robbery.

On these grounds, Teo was found guilty of a single charge of firing two shots at Inspector D'Oliveiro with intent to injure him.

[37] In September 1970, Teo Cheng Leong, who was then incarcerated on death row at Changi Prison, engaged veteran lawyer and opposition politician David Saul Marshall (assisted by J B Jeyaretnam) to represent him in his appeal.

[38] As for the prosecution, then Attorney-General Tan Boon Teik made a special appearance to assist the prosecutor S Rajendran,[39] and Tan argued that the appeal should be dismissed as the jury system was completely abolished on 5 January 1970, which meant that Teo did not have a vested right to a jury trial and he could only be entitled to a trial by two judges at the High Court.

[47] After losing his final death row plea, 38-year-old Teo Cheng Leong was hanged at Changi Prison on one Friday morning in May 1971, but the exact date was unknown.

[48] Two years after Teo was put to death, in November 1973, the Arms Offences Act was passed as a replacement of the previous firearm law to prescribe the mandatory death penalty for unlawful use of firearms (including the offence Teo was convicted for), which made life imprisonment no longer allowed as a penalty for such crimes.

[50] As for Teo's three accomplices, both Khoo Meng Hwa and Ng Chwee Bock were released from prison since 1979, while the fourth robber remains on the run as of today.