A 67-year-old man with the mental age of a young child killed another mentally disabled man by pushing him over after a row, the High Court heard. Cheung Kam-yau is accused of the manslaughter of 68-year-old Yiu Keung-shing in April last year at the Christian Family Service Centre, where both men had been long-term residents. The seven-strong jury found Cheung, who napped through some of the proceedings yesterday, was unfit to stand trial due to his mental disability. However, the jury was told to consider whether Cheung committed the act. If they found he did, the judge would decide whether he should be put into a mental hospital, under a guardianship order or discharged. Tighten supervision of those who care for the mentally ill CCTV footage of the incident on April 3 last year showed Cheung standing facing his bedroom door, before walking over to Yiu and pushing him onto the floor, causing him to hit his head. Yiu was taken to hospital after the incident, and died almost three weeks later from head injuries caused by blunt force trauma, a pathology report showed. The pair had a row before Cheung, now 68, pushed Yiu over, prosecution lawyer Richard Donald said. “What the argument was about we will never know,” he added. The court heard both men had a level of intelligence similar to that of a four year old, and communicated in single words or simple sentences, but there was no evidence of previous fights between them – or of either of them being violent, Donald said. Tsang Suet-ki, the nurse on duty, said she had seen them “taking the mickey” out of each other but there had been no arguments. “Both of them were simple and pure in their usual activities. It appeared to me they were both pretty passive,” she said. On the day, she heard a faint sound, and rushed out of the room she was in to find an unconscious Yiu lying on the floor. “From his eyes, I noticed that he looked very dull,” Tsang said. With 50 residents, disputes arose occasionally at the hostel, manager Cheuk Wing-yi said. Edwin Choy, defending, questioned whether there was sufficient proof to show the actions of Cheung had caused the death. “Death is of course very regrettable and of course Mr Yiu died in rather regrettable circumstances,” he said, noting that the jury could clearly see the incident in the CCTV footage. “The point I would ask you to focus on was causation … can you be very, very certain?” Choy asked. Mr Justice Kevin Zervos is expected to give direction to the jury today before members retire to consider their verdict.