SINGAPORE - A 69-year-old retired aircraft technician, who developed delusional beliefs that his family was trying to harm him, decided to take a pre-emptive strike by killing his wife of 36 years, the High Court heard on Friday (Sept 8).

Kong Peng Yee pleaded guilty to a charge of culpable homicide by slashing Madam Wong Chik Yeok's head, first using a knife and then a chopper, at their Sengkang home on the afternoon of March 13 last year.

He was initially charged with murder but the charge was reduced, as a psychiatric assessment by Dr Kenneth Koh from the Institute of Mental Health found that his mental responsibility for actions had been substantially impaired by his psychotic delusions.

Kong's psychotic state could have its origins in severe depression following mild physical impairments after his eye surgery, said Dr Koh's report in April last year.

A further report in May this year said Kong had a "brief psychotic episode" at the time.

Kong, who was put on anti-psychotic and anti-depression medicine in prison, no longer suffers from the delusions.

The court heard that Kong and Madam Wong, 63, lived with their younger daughter Yanni, 27, in Compassvale Crescent. Their older daughter Annie, 36, lived elsewhere.

In January last year, Kong underwent cataract surgery. Over time, he began to associate various other ailments, such as constipation, weakened knees and insomnia, with his surgery or his food intake.

He refused to take laxatives, believing they were poisonous. When his wife and younger daughter made him drink prune juice for his constipation, he believed they were trying to torture him.

On March 12 that year, after collecting health check-up results, he felt someone was trying to harm him or that he was going to die from some illness, even though the report was not adverse.

When Kong and his wife spent the night at Annie's place, he told her to take care of her younger sister if he was not around. He also told Annie that he did not think she was his biological daughter but did not want her to go for DNA testing.

At church the next day, a Sunday, Kong made incomprehensible noises, ending with "mad already" while they were in the lift.

When Kong and Annie ran into a pastor, he blurted out something to the effect that God wanted him to return his daughter to the rightful parent. During the sermon, he told a stranger next to him that people were poisoning him.

After church, Annie drove her parents home and left to meet Yanni.

Kong, who had taken a nap, claimed that he woke up to roaring sounds. He walked to the kitchen, took a knife from the sink and stabbed Madam Wong in the back while she was folding some clothes in the living room.

He moved to her front and continued stabbing her. When the knife dropped to the floor, he went to the kitchen to get a chopper and continued attacking his wife, stopping only when he realised she was dead.

Kong phoned Yanni, but she missed his call. He then called his younger sister and told her he had killed his wife. He told his sister to call the police and distribute his money to his two daughters.

He also wrote on a piece of paper how his assets should be distributed.

When Yanni called him back, the first thing he said was "I killed Mummy". When she told him not to talk nonsense, he replied, "Already killed".

Annie drove back to the flat and called the police, while Yanni kept her father on the phone.

When they reached the flat with police officers, Kong was sitting on the sofa in blood-stained clothes, while Madam Wong was lying motionless on the bloodied floor.

An autopsy noted 189 injuries, including knife wounds and bruises, mostly concentrated around Madam Wong's head and neck. She bled to death from multiple slash wounds to the head.

Kong told police that he believed his family would not look after him if he was unwell, that Annie had reconciled with her "real" parents, and that he should kill his wife first because his family might want to kill him.

He said that on the day in question, his mind told him to "make sure she die" and that he was "happy" on realising that she was dead, the court heard.

The case was adjourned for sentencing after Justice Choo Han Teck said he would like to ask Dr Koh some questions.

Deputy Public Prosecutor Sarah Shi sought at least nine years' jail, while defence counsel Sunil Sudheesan asked for five years' jail.