Court rejects new self-defense claim and upholds sentence over fatal Sengkang flat dispute.

Singapore’s highest court has upheld an 18-year jail sentence in a fatal family dispute, rejecting arguments that the offender’s mental impairment and claimed fear of her adoptive father justified a shorter term.

Court of Appeal Upholds Sentence
The Singapore Court of Appeal on September 16, 2026, dismissed Tan Qiu Yan’s appeal against her 18-year prison sentence for killing her 67-year-old adoptive father, Tan Ah Bang. The 35-year-old Singaporean had sought a reduced sentence of between 12 and 15 years. The three-judge panel found that the original sentencing decision was neither legally wrong nor manifestly excessive.

Flat Ownership Drove the Dispute
Court findings showed that Tan’s adoptive mother, Koh Li Hua, had told her before dying in August 2022 that she would leave her share of the family flat to her. However, Tan Ah Bang automatically became the sole owner after his wife’s death. Tan later became convinced that her father would deprive her of the property and force her out, leading to repeated arguments about the Sengkang flat and other family assets.

Tan Bought Chopper Months Before Killing
According to court documents, Tan bought a chopper in September 2022 and intended to use it if her father did not transfer ownership of the flat. On November 3, 2022, she again asked him to share ownership with her, but he refused. She later attacked him in their flat and subsequently contacted the police, who arrested her.

Mental Disorder Reduced Criminal Responsibility
Tan pleaded guilty in July 2025 to culpable homicide not amounting to murder and qualified for the partial defense of diminished responsibility. She was found to have suffered from persecutory-type delusional disorder with a background of schizoid personality disorder at the time of the offense. Her lawyers argued that the extent of her mental impairment justified a shorter sentence.

Judges Reject New Motive Claim
During the appeal, Tan argued that she killed her father because she believed he intended to kill her. The Court of Appeal rejected that claim, noting that she had not previously raised it and finding that her central motivation remained the dispute over ownership of the flat. Justice Hri Kumar Nair also noted that Tan had delayed acting for about two months after purchasing the chopper, which the court considered evidence that she retained some ability to control her actions.

For Singaporeans, the decision confirms the Court of Appeal’s view that Tan’s mental condition had already been appropriately reflected in the 18-year sentence while still accounting for her responsibility for the killing. For Indonesian readers following Singapore’s legal system, the case also shows how the courts can consider diminished responsibility without removing criminal liability altogether.

Sources: Mothership (2026) , CNA (2026)

Keywords: Sengkang Killing Case, Tan Qiu Yan Appeal, Singapore Court Of Appeal, 18 Year Jail Sentence, Culpable Homicide Singapore, Sengkang Flat Dispute