A DRUG charge should never have been brought against a man who did not realise the prescribed tranquilliser to settle his nerves contained an ingredient recently listed as a dangerous drug, the High Court heard yesterday. Tsui Kin-ping, 35, said he had been wrongly advised to plead guilty by counsel representing him at his trial, when he had a perfectly good defence to rebut the allegation. Since the Crown did not support the conviction, it was quashed by Mr Justice Leong who declined to order a retrial and pointed out that no layman would take the pills prescribed by a doctor for analysis. Mr Tsui, a construction company owner, had pleaded guilty to a charge of possession of a dangerous drug and was given an absolute discharge by magistrate Paul Kelly who also ordered him to pay $750 costs. Mr Tsui was stopped at the Hong Kong-Macau ferry terminal Customs departure hall late on May 9 for a routine search. He was arrested when 73 Valium tablets, containing 0.17 grams of diazepam - a scheduled dangerous drug - were found on him. Asking the court to allow Mr Tsui to reverse his plea and quash the conviction, Gerard McCoy said his client had been involved in a traffic accident some years ago and had been taking Valium since 1988 to calm his nerves. The drug had been prescribed in both Hong Kong and China, but Mr Tsui had no idea that it contained an ingredient which had been recently listed as a dangerous drug. When he appeared before Mr Kelly, he was wrongly advised to plead guilty by his trial counsel who took the view that there was no defence, Mr McCoy said. While ignorance was no excuse, intention was always an element in almost every offence, he said. The police should never have charged Mr Tsui in the first place and the case should never have come to court, Mr McCoy said. Yasmin Mahomed, for the Crown, said the police should have asked the Legal Department for advice and conceded that, given Mr Tsui's background, the case should not have proceeded against him.