The issue of the admissibility of improperly obtained non-confessional evidence in criminal proceedings has been the subject of considerable academic discussion. However, much of the discussion in England has been confined to an exploration of the deficiencies and internal inconsistencies of the English law in the area. In particular, the House of Lords decision in R v Sang has been subjected to intense scrutiny and criticism. Little has been written which examines the theoretical issues associated with the problem of improperly obtained evidence, with view to laying down foundations for a new approach. It is this task which I seek to undertake here. First, it will be demonstrated that the major Anglo- American legal systems have all abandoned rules ofmandatory inclusion and mandatory exclusion of improperly obtained evidence in favour of more flexible positions whereby such evidence is to be admitted in some circumstances but excluded in others. This suggests that rules of mandatory inclusion and mandatory exclusion have been perceived to be undesirable.