LEGISLATOR Dr Huang Chen-ya has called on the Attorney-General Jeremy Mathews to tell the Legislative Council why his department dropped corruption charges against a mainland official. On Tuesday, the department decided to drop the case against Liu Zhongguo, former managing director of the Guangdong International Company, partly because heart disease prevented him from attending the trial. But Dr Huang, a United Democrat, said there was no indication that Mr Liu was examined by a Hong Kong Government cardiologist to determine whether his illness was so severe that the trial should be stopped. He said there had been cases of defence witness claiming terminal cancer or dementia in the defendant, and the trial being terminated. Yet after the trial was halted, the accused had remained in apparent good health. ''It is doubtful whether the Legal Department has fully utilised the expertise available in the public medical service to question and ascertain whether the medical opinion called by the defence were correct or reliable. ''These cases have all undermined public confidence in legal justice in Hong Kong,'' Dr Huang said. He asked the Legal Department to produce a report on the details of the decision to drop the case against Mr Liu, and review the procedures and ability of the department in dealing with legal cases involving medical evidence. A department spokesman said that it was not common practice for it to comment on individual cases. She said the department had verified medical documents issued by a mainland doctor to certify Mr Liu's heart disease.