On 22 April 1972, Poon Sai Im (潘世英 Pān Shìyīng), a 58-year-old provisions shop owner who lived on the island of Pulau Ubin, Singapore, was ambushed by two men, who had gone from mainland Singapore to the island to rob her of money, cigarettes and gold items. When one of Poon's attackers went into the room to look for valuables, the other attacker, 19-year-old Mohamed Yasin bin Hussin, alias Rosli, took upon himself to rape the victim and while doing so caused the elderly victim to die from fatal rib fractures (caused by Yasin sitting on top of her). Both men were eventually arrested nine months after the case and tried for murder.

Yasin was initially found guilty of murder and subjected to the death sentence (the other man was convicted of and jailed for robbery), but before he could be executed, Yasin won his appeal to the Privy Council in London. He was subsequently taken to court to be tried for rape and consequently spent ten years in prison before his release in 1983. Yasin's case was a subject of debate and question in Singapore's criminal law regarding the definition of murder under Section 300(c) of the Penal Code, in which the offence of murder constitutes one's intentional causing of fatal injuries to a person despite having no intention to kill.

In early April 1972, Mohamed Yasin bin Hussin (born 1953), alias Rosli, then 19 years old, formed an intention to rob a 58-year-old shop owner from Pulau Ubin. The shop owner was a widow named Poon Sai Im, who made a living by selling provisions in a shophouse. Her business had earned her quite some profit that considered her a rich person.

Knowing that Poon was quite wealthy and kept a lot of money in her house, Yasin approached his friend and fellow labourer, 25-year-old Harun bin Ripin^{[lower-alpha 1]} (born 1946) to join him in the robbery attempt. Harun initially neither agreed nor declined the request, but eventually on 22 April 1972, he agreed to go along with Yasin's plan. A third man, only known as Maarof, was initially also approached to join the both of them, but he declined, saying that he was not interested.^[1]

That night, Yasin and Harun rowed a sampan boat from Changi Point Jetty to Pulau Ubin, and both arrived at the beach nearby Poon's house. After reaching the house, Harun devised a plan to lure Poon out of the hut. Yasin then executed the plan and went to Poon's chicken pen where he disturbed the chickens, which led to Poon unlocking her door and came out. Upon the appearance of the woman, Yasin and Harun made their move and caught hold of Poon and covered her mouth to prevent her from shouting.^[2]

As the two men brought her inside the house and pinned her down, Harun left Yasin alone to go search for items to steal in the other parts of the house. As Yasin was struggling to restrain Poon, he looked down and noticed that Poon's baggy trousers had slipped off her waist, exposing her naked lower half. Upon caught sight of it, the teenager formed an impulse to have sexual penetration and thus began to take off his trousers to rape the elderly woman. During which, Yasin had sat onto the chest of the victim and covered her mouth to stop her from calling for help. It was after he finished raping the woman, when 19-year-old Yasin noticed that Poon had become motionless and stopped moving.^[3]

Just at this moment, Harun returned to the kitchen with $40 in cash, 10 packets of cigarettes and a gold ring. Upon seeing Poon's motionless body, he asked Yasin what had happened.^[4] After Yasin told him that he had raped the woman, the two men examined Poon and realised that she was dead. After which, the pair quickly took the corpse to the sea, and they splashed seawater on the deceased Poon's face to revive her, and it failed.^[5] The men quickly boarded their sampan and took the body with them. It was in the ocean that both Yasin and Harun disposed of the 58-year-old woman's corpse into the sea before they returned to mainland Singapore.^[6]

The next day, on 23 April 1972, Poon's youngest daughter Lim Ah Moi went to her mother's house and found that her mother was missing. She informed her boatman husband Ng Tan Tee, alias Tong San, about this and found her house ransacked. The couple then reported it to the police.^[7]

A day later, a fisherman fished out a semi-nude body of a woman and reported it to the police. The police managed to identify the deceased woman as the missing Poon Sai Im. Initially, the police presumed that she may have accidentally drowned in the sea, but when the body was taken to Outram Hospital (now Singapore General Hospital) for an autopsy, the truth came out.^{[8][9][10][11]}

Forensic pathologist and professor Chao Tzee Cheng, who examined Poon's corpse, found that the woman was not dead by drowning but by murder. He found a total of nine fractures on the victim's ribs, which he ascertained as the cause of death as these fractures were sufficient to cause cardiac arrest and thus lead to death given her age and the bones' resulting fragility. These fractures were caused by compressions applied on her chest, which was actually a result of Yasin sitting on Poon's chest while he restrained and raped her before her death. Professor Chao also found bruises on her face and wrists, which were defensive injuries caused by Poon trying to defend herself against her attacker(s) and her being punched or hit by a blunt object. He also told police that the woman was sexually assaulted, as there were abrasions and injuries on her vaginal wall and bruises on her thighs, showing that someone used force to pry her thighs open and presumably raped her. These were presented in the forensic report which Professor Chao submitted to the courts. Police investigations took place but there was no progress for the next nine months due to the lack of clues in the case.^[12]

After he was sentenced to death, Yasin submitted an appeal against the death sentence to the Court of Appeal. On 4 November 1974, however, the three judges hearing the appeal - T Kulasekaram, Tan Ah Tah and Chief Justice Wee Chong Jin - found that there was no doubt that Yasin had intentionally caused the nine fatal broken rib injuries on 58-year-old Poon, which therefore fitted the definition of murder under Section 300(c) of the Penal Code and thus appropriate for Yasin to be convicted of murder by application of the law. They also accepted the forensic evidence by Professor Chao, as argued by prosecutor Glenn Knight (who replaced Pala Krishnan and assigned the case), that the fractures were caused by compression of the chest with some force, This compelled the judges to dismiss Yasin's appeal.^[31][32]

After the failure of his appeal at the Court of Appeal, Yasin was left with two remaining avenues of appeal - one was to the Privy Council in London and another was to appeal for a pardon from the President of Singapore - which would enable him to escape the gallows if successful. Yasin was later granted leave to appeal to the Privy Council, which heard his appeal on 17 May 1975.^[33]

On 4 February 1976, Singapore's national newspaper The Straits Times reported that Yasin had successfully escaped the death sentence when the Privy Council allowed his appeal against the death sentence.^[34] In their verdict, the three Privy Council judges, led by Lord Diplock, found that there was no evidence to suggest that Yasin had intended to cause the death of Poon when he sat on her chest. They also said that while the prosecution had duly proven that Yasin knew what he was doing and intended to sit on the chest (which was voluntary), they commented that it failed to give rise to the contention that Yasin had intended to cause the fatal rib fractures on Poon or knew that the injuries he caused to the victim would be sufficient to kill her.^[35]

The three Lords further scrutinized the case and stated that the prosecution's burden of proof was to show that Yasin had indeed sat on the chest of Poon to stop her from struggling and in the process, intentionally caused the grave injuries that were medically possible to cause the death of someone of Poon's original age and build even if Yasin himself genuinely did not have the medical knowledge of what he was doing, and they said the prosecution failed to fulfill it, since there was no evidence of whether Yasin had indeed sat on Poon's chest and the judges only inferred that Yasin did so from the forensic evidence provided by Professor Chao.^[36]

As such, the Privy Council in London dismissed the murder charge and revoked Yasin's death sentence. Instead, they found him guilty of causing death by a rash or negligent act not amounting to culpable homicide under Section 304A of the Penal Code. The case was remitted back to the Court of Appeal in Singapore for re-sentencing. It was also confirmed that Yasin would be facing a re-trial for the rape of Poon while causing her to die.^[37][38][39]

On 18 May 1976, Yasin was sentenced to the maximum of two years' imprisonment for the reduced charge he was convicted of.^[40]

Following the reprieve from death row by the Privy Council, Yasin was soon brought back to court in Singapore, with the prosecution charged him with raping Poon. DPP Sant Singh became in charge of the case, and defence lawyer Murugason became Yasin's new lawyer for the retrial.

Yasin claimed trial in the High Court for rape on 9 May 1977. His former accomplice Harun, who was then serving his 12-year sentence in Changi Prison, was called by the prosecution to be a witness against Yasin. Harun, who took the stand on 11 May 1977, told the court that Yasin had done the act while he was in another room ransacking for valuables, and claimed that when he returned, he asked Yasin what happened, with Yasin replying to him that he had intercourse with the woman. Yasin denied telling Harun that he had sexually penetrated the elderly woman, and insisted that he had not raped the woman and only intended to come to Pulau Ubin with Harun to steal from Poon, who kept a lot of cash in her home.^{[41][42][43][44]}

On 12 May 1977, Yasin's trial for rape ended. High Court judge A. P. Rajah determined that Yasin had indeed intended to have sex with Poon against her will. Despite so, Justice Rajah fell short of finding Yasin fully guilty of rape and instead convict the former labourer of attempted rape, as from the nature of the forensic evidence, he was not entirely satisfied that Yasin had sexual intercourse with the victim while she was still alive, and thus gave Yasin the benefit of the doubt. Despite not finding him guilty of rape, Justice Rajah admonished Yasin for committing such an atrocious crime on the unfortunate Poon, in his own words, "However, I find that you manifested this intention to have intercourse with the woman, and in furtherance of your intention, you did a number of acts against the deceased with a view to attaining your objective."

For his conviction of attempted rape, Yasin was sentenced to eight years' imprisonment for the crime. The sentence was backdated to the date of his arrest on 10 February 1973.^[45][46] The two-year sentence which Yasin received for killing Poon was to run consecutively with the term of eight years.

In the aftermath of Yasin's case, the Privy Council's verdict, titled Mohamed Yasin bin Hussin v Public Prosecutor, became one of the notable judgements that questioned the context, definition and existence of murder under Section 300(c) of the Penal Code (under which Yasin was originally convicted of).

Original text of Section 300(c) (Extracted from the Penal Code):

(c): if it is done with the intention of causing bodily injury to any person, and the bodily injury intended to be inflicted is sufficient in the ordinary course of nature to cause death^[52]

There were discussions related to the Privy Council's verdict regarding the need to find a person guilty of murder with no intention to kill. The verdict by the Privy Council was in the direction of a "precise injury" approach, which was produced by the three Lords who felt there was a lack of intention on Yasin's part to cause the precise injuries to cause Poon's death. It contradicted the Singaporean courts' normal procedure to convict a person of murder with a "broad injury" approach, which they adopted from an Indian court case verdict Virsa Singh v the State of Punjabi relating to find a person guilty of intentionally inflicting a serious injury which is sufficient to kill regardless of whether he/she knew the fatality of the injury even if he/she had no intention to kill, leading to confusion among the judges in Singapore

Being constantly cited in later murder verdicts in later years since 1976, the Yasin verdict was one of the judgements in which it questioned the problematic application of Section 300(c) in court cases to find a person guilty of murder with no intention to cause death, and its wording gave rise to ambiguity to its real definition. Other cases like Lim Poh Lye and Tan Chee Hwee had also, like Yasin's case, asked such a question about the section, and it contained the judges' own reservations about sentencing an offender, who never intended to kill in the first place or had any knowledge that death would arise from the injuries caused, to death for murder. There was also some criticism directed at the Yasin verdict for not giving a precise explanation about the precise injury approach or its decision, in relation to the context of Section 300(c) (e.g. Tan Cheow Bock v PP).^[53]

The Privy Council's verdict over Yasin's case is included as a case study in the syllabus of Singapore's law courses in universities such as the National University of Singapore and Singapore Management University. It is also included as one of the subjects tested in the bar examinations in Singapore.^[54][55][56]

• Capital punishment in Singapore
• List of major crimes in Singapore