SINGAPORE - A cleaner who had been harassed by his former neighbour's "voice" slashed the victim to "teach him a lesson", a court heard.

On Tuesday, Wong Keng Foong, 59, was jailed for four years after he admitted causing grievous hurt to Mr Low Chin Lye, a taxi driver, with a chopper at Sin Kee Heong Coffeeshop at Commonwealth Drive on May 31 this year.

The 61-year-old victim suffered cuts on his neck, shoulder and hands. He was warded for a week and given medical leave for about three months.

A district court heard that the victim was sitting in the coffeeshop to wait for his wife to have breakfast that morning when he suddenly felt something cold on his left neck.

He turned his head and saw Wong who shouted "I will chop!" in Hokkien .

When the victim tried to stand up, he fell and was attacked by Wong on his left shoulder and neck area.

When the chopper fell from Wong's hand, Mr Low picked it up and tried to fight back. The two scuffled and fell. They were separated by some patrons at the coffeeshop.

Investigation showed that earlier that day, Wong decided to make a trip to Commonwealth Drive area as he wanted to look for the victim and "teach him a lesson".

When he saw Mr Low sitting alone at the coffeeshop, he decided to look for a chopper and found one at a roasted meat stall.

Investigation also showed that Wong had been constantly "harassed" by the victim's "voice" and felt he was being pestered by the victim's "spirit". He launched the attack to rid himself of the "voice".

Wong, who was unrepresented, said he had been an Institute of Mental Health patient since 1985, and suffered injuries that day.

District Judge Salina Ishak, who backdated Wong's sentence to July 7, said although Wong had schizophrenia, he was not of unsound mind at the time.

The maximum punishment for the offence is 15 years' jail, fine or caning.