Deputy Judge Daniell adjourned sentencing until August 27, pending a background report. Ma's bail of $20,000 was extended.

Acting Senior Assistant Crown Prosecutor Stephen Wong said that at the time of the incident, the couple were living with their daughters and a 13-year-old grandson in a flat in Tai Po.

The couple had six children aged between 35 and 46.

The court was told that on June 17 last year, the grandson returned from school and could not find the couple in the flat. He discovered the toilet door was locked and called the police.

They found the defendant sitting unconscious on the floor holding a pair of scissors on his chest. His wife was lying next to him. There was a strong smell of propane gas.

Wong was certified dead on arrival at Tai Po Jockey Club clinic.

The cause of death was found to be multiple stab wounds with injuries to the heart, lung and liver. The defendant was treated for a stab wound to his liver.

He admitted under caution that he and his wife had had a dispute over her request for food money, which he had refused.

He claimed his wife had become emotional.

The court was told he then saw his wife enter the toilet. He went back to his room to rest. Half an hour later, he heard his wife shouting for help and when he pushed open the toilet door, he found her bleeding profusely.

She was holding a pair of scissors, which he used to stab her twice, the court was told.

He then dragged her to the living room, where he tied both their hands with electrical wire and attempted to electrocute himself and her by inserting one end into a socket.

After that failed, Ma took a gas stove and cylinder from the kitchen into the toilet and dragged his wife inside, the court heard.

Mr Wong said the defendant sealed the window of the toilet with pieces of cloth, then washed away the blood stains and mopped the floor of the sitting room.

In the toilet, he cut the plastic tube and released the gas from the cylinder. He then stabbed himself.

The court was told the defendant was examined by two psychiatrists, who both believed he had been suffering dementia for several years.

His history suggested he had suffered intellectual impairment and deteriorating memory function before committing the offence.

Mr Wong said experts felt that because of this abnormality of mind, Ma could have reacted in an exaggerated and disorganised way at the time of the offence.