An elderly man with signs of a brain abnormality said he chopped his nagging wife to death because he could no longer tolerate her after more than four decades of marriage. Ng Kwok-yuen, 79, wept yesterday as he pleaded not guilty to murder but guilty to manslaughter. He told police his wife, So Yuen-yee, told him he was ugly and never helped when he was sick, the Court of First Instance heard. So had more than 30 chop wounds to her body. Mr Justice Alan Wright accepted the plea of manslaughter by reason of diminished responsibility and adjourned sentencing to September 14 pending a further psychiatric report. A psychiatric report read in court yesterday said Ng suffered from a condition known as frontal lobe syndrome, which could affect judgment, and was probably in an abnormal state of mind when he killed So, 68. Ng chopped So, whom he married in 1964 and with whom he had a daughter and two sons, to death while she was standing in the living room of their flat last August, according to a summary read in court. 'The accused thought that he would be put in jail, but went ahead because he had already suffered for 40 years,' the court heard. Ng, who has been a courier, waiter, delivery worker and cleaner, told police he could no longer tolerate his wife and that they had never got along since they were married. She constantly nagged and quarrelled with him, and was unappreciative of him. He cooked and washed the dishes while she would watch TV, and when he was sick, she would not attend to him, he said. He bought the chopper about three months before the killing for the purpose of chopping his wife to death, he told police. 'It appears that he did have the intention to kill his wife ... however, the intention was brought about by a gross impairment in judgment,' the psychiatric report said.