A CORONER'S jury yesterday returned a verdict of death by unlawful killing in the case of a 25-year-old Vietnamese inmate who died of stab wounds at Whitehead detention centre two years ago. Coroner Mr Warner Banks heard that inmate Mr Vu Minh Tam, who was found in an open space between huts 7A and 8A of the camp, died of a stab wound to the chest in the early hours of May 27, 1991. Mr Vu was carried to the camp clinic and then to the Prince of Wales Hospital where he was certified dead before arrival at 3.05 am. Fellow inmate Mr Nguyen Ba-hop, 37, a disciplinary prefect in the camp at the time of the incident, said he patrolled huts 7A and 8A at about 2 am that day. He said he was about 10 metres away when he saw a Vietnamese male inmate rush to Mr Vu and stab him in the back with a home-made knife. The assailant disappeared quickly, he added. ''At that time, I saw the deceased Vu Minh Tam falling down. He was stabbed to death, but I do not know why,'' Mr Nguyen said. He contended that it was an accident, but later conceded: ''I don't know the cause of the incident and I did not see clearly. As this took place very quickly, I can't say whether it was an accident or otherwise.'' Based on the evidence from two key witnesses, police had charged inmate Mr Luong Viet Loc with the murder of Mr Vu. Last November, Mr Luong was acquitted of the charge in the High Court after one of the witnesses who saw the stabbing, Mr Nguyen, gave evidence inconsistent with his earlier police statements. It is understood the other witness, Mr Vu Van Tam, 27, was voluntarily repatriated to Vietnam on January 10. Mr Vu Minh Tam's elder brother, Mr Vu Duc Thinh, 31, said he and his brother sailed on a boat from northern Vietnam to Hongkong in August 1988. Asked whether there was anything to suggest his brother's death was not an accident, he said: ''My brother was stabbed to death. Obviously it was a murder. It cannot be an accident.'' His evidence was echoed by senior forensic pathologist Dr Hau Kong-lung, who said it was unlikely that Mr Vu's death was accidental. Dr Hau, who prepared a post-mortem examination report on Mr Vu, said: ''The stab wound on the upper back of left chest was directed forwards, downwards and to the right. ''The total depth of the wound track was about 23 centimetres.'' He said the stab wound penetrated through the inner lower part of the left shoulder blade into the left chest cavity, the upper part of the lower lobe of left lung and the inner surface of the middle of the breast bone. Detective Senior Inspector Chong Siu-hing, attached to the District Crime Squad in Sha Tin at the time of the incident, said only two of the witnesses he had interviewed said they saw the deceased being stabbed in the back. He said most of the Vietnamese witnesses were reluctant to help the police, possibly because of fear of revenge.