Authorities' power to destroy intelligence obtained by phone tapping could deprive defendants of evidence that might be useful to their defence and their right to a fair trial, lawmakers argued yesterday. Their concerns were expressed as the bills committee studying the new covert surveillance law continued a marathon effort to finish its task before the Legislative Council recess on July 12. The committee completed its clause-by-clause scrutiny of the bill in a five-hour meeting. The proceedings were dominated by concerns about the implications for fair trials because of the rules governing the admissibility of evidence obtained by covert surveillance. But the bill has yet to go through amendments proposed by the government. One lawmaker said the regulations relied too much on the 'conscience of prosecutors' to do the right thing, while another said authorities could effectively destroy evidence that could have provided a criminal suspect with an alibi. The issue was thrown into controversy in an ICAC case in which prominent lawyers Kevin Egan and Andrew Lam Ping-cheung were jailed last week. Lawyers for Lam had claimed that crucial evidence intercepted by the ICAC was destroyed, despite a letter from Lam seeking its preservation. The bill provides that products of covert surveillance, such as hidden cameras and tracking devices, are admissible, but not products of phone tapping. Evidence obtained by phone interception must also be destroyed as soon as possible - unless it contains evidence supporting innocence, such as an alibi for a suspect. 'It is crucial that the secrecy surrounding the conduct of this technique and the product be preserved,' said Ian McWalters, senior assistant director of public prosecutions for the Department of Justice, adding that this would override the prosecution's disclosure requirement. But Democrat James To Kun-sun said it would be unfair to destroy the material and then inform the defence that it contained evidence which might help its case. Permanent Secretary for Security, Stanley Ying Yiu-hong, said the purpose of intercepting communications was intelligence gathering and investigation. 'Once that purpose is served, the product will be destroyed.' Democrat Albert Ho Chun-yan said it should be mandatory in the law for prosecutors to disclose such evidence to the judge. 'Otherwise, we are relying on the conscience of the prosecutor, which is not good enough,' he said. Mr Ying said the administration would consider the mandatory requirement. A punishing schedule of meetings is planned today and tomorrow so the bill can be endorsed in time to be passed before Legco goes into recess.