The two victims were 24-year-old Phoon Ah Leong and his 56-year-old mother Hu Yuen Keng, who were both operating a stall selling roast duck and noodles at the centre itself.

[3][4][5] Inspector Leong Kong Hong became in charge of the police investigations, and they managed to identify the suspect, who was arrested at Singapore General Hospital where he sought treatment for an arm injury he sustained from the earlier stabbing.

[1] The killer was a 35-year-old hawker named Haw Tua Tau, who operated a neighbouring stall selling roast-pork, satay and oyster omelette.

[1] During the same month of his arrest, Haw Tua Tau was charged with two counts of murder in relation to the double deaths at Margaret Drive.

[11][12] One of the witnesses, Soh Poh Choo (苏宝珠 Sū Bǎozhū), who was the helper of Haw's hawker stall, said she tried to intervene but got hurt by Phoon's brother.

[16] He testified that he was approaching Phoon with the intention of telling him to clean the table properly and sweep up the duck bones that dropped onto the floor.

Overall, Haw's defence was he had accidentally stabbed the victims to death, and that he was not aware that he had a weapon in his hand when he confronted Phoon over the table cleaning issue.

Haw's wife Chan Lee Kheng (陈丽卿 Chén Lìqìng), who was present in court, reportedly wept as the death sentence was pronounced on her husband.

Diplock, who delivered the verdict on behalf of the panel, stated it was not necessary for the prosecution to meet the criteria of proving a case beyond a reasonable doubt before calling for an accused to put up a defence in court.

[43] After losing his final death row plea, 41-year-old Haw Tua Tau was hanged at Changi Prison in 1982, but the exact date of his execution is unknown.

However, during the appeal of a drug trafficker Arulpragasan Sandaraju in 1996, the Haw Tua Tau test was overruled by a majority decision of four to three from the Federal Court of Malaysia, after it deemed through Arulpragasan's appeal that the burden of proof by the prosecution should be the higher requirement of proving all elements of a case beyond a reasonable doubt at the end of its case, before the defence should be called to give an answer, rather than deploying the Haw Tua Tau test.

This led to the acquittal of Arulpragasam for trafficking 1.2kg of diamorphine,[50] and it also enabled a hockey coach M Mahendran to succeed in his appeal to overturn his conviction and sentence of ten years' jail with four strokes of the cane for raping a student.

Some lawyers in Singapore also questioned the use of the Haw Tua Tau test in many cases as they felt it made the prosecution having an easier job in securing a conviction for an accused, and they called for a higher tier of requirement for the prosecution to present a case that was sufficiently proven beyond a reasonable doubt and so sufficient that an accused was bound to put up his defence.

[58] Notably, in January 1995, the case of Haw Tua Tau was referenced to by Malaysian lawyer Karpal Singh, who was defending a convicted gunman Ng Theng Shuang during his appeal against the death penalty.

[63] The test itself was discussed among lawyers, with some agreeing to its application while some also believing that it was more sound to have a case proven beyond a reasonable doubt by the prosecution before calling for the accused to present his defence in court.