Ayako Watanabe had recently joined her husband in Singapore
The Court of Criminal Appeal recorded that Ayako Watanabe arrived in Singapore in December 1969 with her three children to join her husband Hiroshi Watanabe, a mechanical engineer working on reclamation projects. Hiroshi had previously formed an intimate relationship with Mimi Wong while living in Singapore.
On the evening of January 6, 1970, Hiroshi was away working late. Mimi Wong and Sim Woh Kum entered the Watanabe home. Ayako was attacked in the bathroom and died from stab wounds that caused severe blood loss.
The couple's eldest child became an important witness
Ayako's eldest daughter, Chieko, was in the house and saw enough of the incident to identify Mimi Wong and a man. The appellate judgment recounts her evidence and the circumstances in which Hiroshi returned home and learned what had happened.
The prosecution also relied on the conduct and admissions of the two defendants, physical evidence and the circumstances leading to their arrival at the Watanabe home. Both defendants attempted to shift responsibility during the case, but the trial court found them criminally responsible for the murder.
Convictions and the common-intention finding
Mimi Wong and Sim Woh Kum were convicted of murder after trial in December 1970. The court found that Wong inflicted the fatal knife injuries and that Sim participated in the attack and shared the legally relevant common intention.
The appellate court considered whether the evidence supported liability under the common-intention doctrine. It concluded that the trial court had been entitled to find either a common intention to cause Ayako's death or a common intention to inflict the knife injuries that caused her death.
The appeal was dismissed
On July 22, 1972, the Court of Criminal Appeal dismissed the appeal in Wong Mimi and Another v Public Prosecutor. The published judgment left both murder convictions in place.
Later reporting by The Straits Times records that both Wong and Sim were executed on July 27, 1973. That later event is included only as procedural history; the case is classified solved because of the convictions and unsuccessful appeal.
Separating the victim from the sensational narrative
Contemporary and later coverage often focused heavily on jealousy, infidelity and the notoriety of Mimi Wong as the first woman sentenced to death in post-independence Singapore. Those details can obscure Ayako Watanabe herself.
For this archive, the essential facts are that Ayako was a 33-year-old mother who had recently moved to Singapore with her children, was killed in her own home, and that two defendants were convicted of her murder after a full trial and appeal.
Timeline
December 23, 1969: Ayako Watanabe arrives in Singapore with her three children to join her husband.
January 6, 1970: Ayako is murdered at the family home in Jalan Sea View.
December 7, 1970: later established reporting records the convictions and death sentences after trial.
July 22, 1972: the Court of Criminal Appeal dismisses the appeal of Mimi Wong and Sim Woh Kum.
July 27, 1973: later reporting records that both sentences were carried out.
Current status
The murder of Ayako Watanabe is Solved / Adjudicated. Mimi Wong Weng Siu and Sim Woh Kum were convicted of murder, and Singapore's appellate court dismissed their appeal in 1972.