A mental patient who was frequently attacked by fellow inmates died mysteriously in his room of severe internal bruising, an inquest heard yesterday. Coroner David Thomas recorded an open verdict on the death of Choy Tsan-ah, 39, who was found dead on July 6 last year. He said he found the case disturbing because it was not known what caused the bruising. 'I ask the police to consider whether further investigation is warranted in this case,' Mr Thomas said. The Hospital Authority said a thorough investigation into the patient's death had been conducted. It said it would consider Mr Thomas' advice to further boost staff awareness of the need to attend to mental patients. 'The hospital will conduct an overall review on the system of observation.' Choy, who had stayed at the Castle Peak institution for 17 years with mental retardation and schizophrenia, also had bruises on his face, head and chest. A postmortem examination concluded he died of peritonitis. Six ward attendants and nurses on duty at the time of his death testified that they heard nothing from his room. The inquest heard Choy frequently had conflicts with fellow inmates because he snatched their food. Nurse Law Hau-ping said he did not query why Choy was lying on the floor at midnight as he often slept there because of the heat.