Are too many guilty people going free? Some experts believe so, because - they claim -we have to use out of date rules of evidence in our criminal courts. Sir Robert Mark , Commissioner of the Metropolitan Police, has said: Only a small proportion of those acquitted by juries are innocent in the true sense of the word.' At this moment Parliament is considering overhauling these rules. MPs have before them a massive report, produced after eight years' work by the Criminal Law Revision Committee, which recommended important changes. These recommendations have aroused violent controversy in the legal world. Supporters and critics both base their case on what they think is in the best interest of the public. What is in our best interest? Michael Zander , lawyer and Legal Correspondent of The Guardian, explains how the law now stands, what the Committee's proposals are and why the legal profession is so concerned by the proposal to abolish the Right of Silence. This, it believes, would destroy the fundamental principle that ' in this country a person is innocent until proved guilty.' Producer ANTHONY DE lotbinieri