A MAN, who subjected an 111/2-month-old baby to an attack which resulted in four skull fractures, was yesterday found not guilty of murder but guilty of manslaughter by a High Court jury. Mr Justice Keith sentenced Tsui Kai-sui, 31, a seafood wholesaler, to five years' jail for killing his girlfriend's daughter in May last year. The jury also found Tsui guilty of a charge of cruelty to the baby, Lee Po-yan, who had bruises and abrasions to her head, face and body which the court heard were consistent with being pinched. He received a concurrent sentence of 18 months on this charge. The defendant showed no emotion as he limped from the dock. He is a polio victim who moved in with the child's mother, sales assistant Hui Ting-ting, six months before the baby's death. In sentencing Tsui, the judge said the skull fractures which resulted in brain damage could have been caused only by hard and repeated blows to the baby's head. Mr Justice Keith said he appreciated the case had been a tragedy to the defendant, his family and Ms Hui, and that it was Tsui's first brush with the law. ''But the fact is the baby died at your hands when you subjected her to a violent attack,'' he said. It was the Crown's case that the defendant, irritated by the baby's crying, threw her heavily on to a bed and she dropped on to the floor. Po-yan's father was a married man and Ms Hui rented a room in Kai Ming Street, Hunghom, with his financial help. The baby was born in May 1991 and at first was cared for by an agency. A few months later, Ms Hui, who was then 20, got a job as a hostess at a nightclub, where she met Tsui. A month later he moved in with her. On March 28, last year, Ms Hui took back the baby. On May 18, last year, Ms Hui was to begin a new job at a department store and left home at 8.45 am. In a cautioned statement, Tsui admitted he was sleeping when Ms Hui left and became angry because Po-yan was crying, the court heard. He allegedly said he threw her on to the bed. She did not stop crying and he threw her harder on to the bed and she dropped on to the floor. After this, she was quiet and Tsui said he went to the toilet. On his return, he found her breathing short and there was blood on her mouth. He phoned his mother, who told him to take her to hospital. Po-yan was certified dead on arrival at Kwong Wah Hospital at 9.45 am. Tsui told police Po-yan always cried and he admitted he used to pinch her. In testimony, Tsui said he suspected Ms Hui might have dropped the baby the night before and, because he loved her, he decided to shoulder the burden. He later said police had framed and threatened him.