The fate of a criminal trial can be determined by a decision by the trial judge to exclude evidence which has come about by illegal or improper investigative means. An exclusion of a confession obtained involuntarily, or drugs located in an illegal search, can result in the collapse of a case against an accused. Little has been written on a particular species of such evidence, that is, evidence which is derived from evidence which has been obtained by illegal or improper investigative means. Described variously in overseas literature as 'derivative evidence' or 'fruit of the poisonous tree', this species of evidence gives rise to considerations which are peculiar to it when applying the exclusionary rule and discretions. Thus, the second or subsequent confession obtained after in consequence of an improperly obtained confession may require the judge to think differently on the question of exclusion.
This text provides practitioners with a readily comprehensible analysis of the operation of the exclusionary rule and discretions in Australia, including the factors which come into play generally with respect to all evidence illegally and improperly obtained, and more specifically with respect to derivative evidence.